Sustainable Urban Development Master thesis Potentiality, impact factors and solutions for rainwater reuse in Ho Chi Minh City – Case study: Thu Thiem new urban area.

Luận văn Thạc sĩ Trường Đại học DarmStadt Đức Đề tài: Tiềm năng, các yếu tố tác động và giải pháp tái sử dụng nước mưa tại Thành phố Hồ Chí Minh Nghiên cứu trường hợp: Khu đô thị mới Thủ Thiêm. (Tiếng Anh) Water scarcity is one of the most important issues in the world currently. The increasing of population and urbanization leads to find the renewable water source to meet the demand. Rainwater is one of the suitable source for water supply which helps to reduce the exploitation of groundwater and the limited of surface water. Rainwater has been used since thousand years ago. Until now, it has been used in many developed and developing countries to conserve the water sources. In Ho Chi Minh City (HCMC), there are only households who cannot access to the city piped water network use rainwater as a non – potable water and sometimes use it as the potable water source after treating by boiled. It is a waste because the rainfall of Vietnam is quite high. Moreover, using rainwater can also bring other benefits such as preventing floods and conservation the water sources. Rainwater is a free water source, if there is a research for application of recycling rainwater in HCMC, these problems causes by rainwater as well as the water shortage can be decreased. Therefore, this paper studies about impact factors to rainwater in HCMC to answer the question why this city does not use rainwater while the average annual precipitation is high. The factors that hinder the widely use of rainwater are the attitude of residents and the strategies of authorities. Besides, the factors that causes the change in quality and quantity of rainwater are the land use change and the disappearance of catchment areas for rainwater.

Potentiality, impact factors and

solutions for rainwater reuse in Ho Chi Minh City –

Case study: Thu Thiem new urban area.

Le Thi Thuy Hang | SUD2012 – M08

Vietnamese German University

Sustainable Urban Development

Le Thi Thuy Hang

Student Identification: SUD2012 – M08

Course: Sustainable Urban Development

Dipl.-Ing Sonja Dieckmann

Prof Dr.-Ing. Hans-Joachim Linke

Academic Director of MSc.-Study program "Sustainable Urban Development" at the Vietnamese-German-University Ho Chi Minh City

Declaration on the presented work

I declare that all work presented here has been created without assistance of thirdparties and only with the sources and mediums mentioned All material taken from anysources is identified as such

I have not previously submitted this work or any version of it for assessment to anyexamination authority

Darmstadt, 25.11.2014

[Le Thi Thuy Hang] Signature:

5.2 SWOT Analyis of Recycling Rainwater In HCMC and Thu Thiem 31

6 Recycling rainwater in Thu Thiem new urban area 316.1 Basic concept of recycling rainwater master plan in Thu Thiem new urban area 316.2 Criteria for recycling rainwater in Thu Thiem new urban area 316.3 Details of recycling rainwater of Thu Thiem new urban area 31

Water scarcity is one of the most important issues in the world currently The increasing

of population and urbanization leads to find the renewable water source to meet thedemand Rainwater is one of the suitable source for water supply which helps to reducethe exploitation of groundwater and the limited of surface water

Rainwater has been used since thousand years ago Until now, it has been used in manydeveloped and developing countries to conserve the water sources In Ho Chi Minh City(HCMC), there are only households who cannot access to the city piped water networkuse rainwater as a non – potable water and sometimes use it as the potable water sourceafter treating by boiled It is a waste because the rainfall of Vietnam is quite high.Moreover, using rainwater can also bring other benefits such as preventing floods andconservation the water sources Rainwater is a free water source, if there is a researchfor application of recycling rainwater in HCMC, these problems causes by rainwater aswell as the water shortage can be decreased

Therefore, this paper studies about impact factors to rainwater in HCMC to answer thequestion why this city does not use rainwater while the average annual precipitation ishigh The factors that hinder the widely use of rainwater are the attitude of residents andthe strategies of authorities Besides, the factors that causes the change in quality andquantity of rainwater are the land use change and the disappearance of catchment areasfor rainwater

After understanding of the aspects affecting rainwater, this research investigates themaximum amount of water that HCMC can harvest from rainfall The results show that inHCMC, the maximum potential of rainwater is to be 182 liter per capita per day that canserve the non – potable purposes for domestic use In Thu Thiem urban area – a casestudy in this research, the potential of collected rainfall from impervious surfaces is quitelow, only 62 liter per capita per day because most part of this urban area is covered bywetlands However, the rainwater harvesting system is studied to apply in this areabecause the construction costs in lower than construction costs in the built – up area ofHCMC Further, rainwater is storage in the central in the heart of Thu Thiem peninsula.Therefore, the rainwater can provide to meet the demand of residents in Thu Thiem.The cost – benefits analysis and SWOT analysis draw rainwater harvesting system to beone of the alternative water source in HCMC and especially in Thu Thiem The solutionsfor recycling rainwater in Thu Thiem area is illustrated by some schematic figures

I would like to express my gratitude to Prof Hans Joachim Linke who has supervised andhelped me a lot on this thesis as well as gave me a very warm environment during thetime I am staying in Darmstadt, Germany to do my research

I am extremely grateful to my friend William Cheong for grammar correcting of mywriting while he was very busy

And another thanks to Ms Sonja Dieckmann who supported me in this paper

I also thank Dr Chris Merkelbach – my German teacher who taught me how to presentthe thesis as German style, and always encouraged me although I sometimes did notstudy hard in his German class when I had to concentrate on my thesis

And thank my lecturer and friends: Ms Quynh Thu, Thiep, Arman, Quang, Huong, Tan,Kiet, Quynh and Nam - those who helped and suffered me during the time I am here forthe thesis

And I give thanks to my family, and my close friends in Vietnam, with theirencouragement, I feel more motivated to finish this thesis

Another thanks, I would like to give to Dr Son Pham – my program cooperator and Ms.Hoang Anh – the program assistant who supported me for my studying issues inVietnamese German University

I give my special thanks to Ms Ute and her family, Prof Hollborn and his wife, Dr.Weidele, and Mr Hickel who introduced German culture to me and showed me how kindthe German people are That makes the time I worked with this thesis here was not soboring and stressful

Lastly, I need to thank DAAD (German Academic Exchange Organization) that supported

me the scholarship so that I could survive to write my thesis in this country

Finally, I have just done my Master thesis Thank you all

Darmstadt, 25th November, 2014

List of Abbreviation

DONRE Department of Natural Resources and Environment

DPA Department of Urban Planning and Architecture

HCMC Ho Chi Minh City

HIE Heat Island Effect

ITPC Investment and Trade Investment Center

LID Low Impact Development

RWH Rainwater Harvesting

Sasaki Sasaki Associates, Inc

SAWACO Saigon Water Supply Cooperation

SUHI Surface Urban Heat Island

USD United States of America Dollar

WSUD Water Sensitive Urban Design

WSI Water Stress Index

WTP Water Treatment Plant

List of Figures

Figure 1-1 Aerial view of Thu Thiem area 7

Figure 1-2 Master plan of Thu Thiem new urban area 8

Figure 3-1 Annual precipitation in HCMC from 2005 to 2010 26

Figure 3-2 Relationship between impervious cover and surface runoff 27

Figure 3-3 Results of urban expansion in the Northern part of Ho Chi Minh City in 1989, 1989, 2002 and 2006 from remotely sensed data 29

Figure 3-4 the change of temperature from 1989 to 2006 29

Figure 3-5 Percentage of water usage in households 31

Figure 4-1 A schematic diagram of a rooftop rainwater harvesting system 31

Figure 6-1 Basic concept of rainwater recycling in Thu Thiem 31

Figure 6-2 Underground cisterns in Thu Thiem new urban area 31

Figure 6-3 Cross Section of Thu Thiem new urban area 31

Figure 6-4 Cross Section of Thu Thiem new urban area 31

Figure 6-5 Typical Installation of rainwater harvesting system Figure 6-6 Green Roofs for rainwater harvesting 31 Figure 6-7 Harvested rainwater for car washing in commercial buildings 31

Figure 8-1 Flooding areas in HCMC 31

Figure 8-2 Water quality index at 10 water canal monitoring stations in HCMC (November 2012) and at 22 water river monitoring stations in Saigon and Dong Nai river (December 2012) 31

Figure 8-3 Water quality Index 31

Figure 8-4 Average monthly rainfall for HCMC, Vietnam 31

Figure 8-5 Relative frequency of various types of precipitation over the course of a typical year 31

Figure 8-6 Maximum precipitation per day 31

Figure 8-7 Water tariff per month 31

Figure 8-8 Grading and drainage plan 31

Figure 8-9 Water and Wastewater plan 31

Figure 8-10 Collective Infrastructure Network Plan 31

Figure 8-11 Current situation in Thu Thiem new urban area - April 2014 31

Figure 8-12 New buildings in Thu Thiem new urban area - April 2014 31

List of Tables

Table 2-1 Percentage of water sources for 24 districts in HCMC 15

Table 2-2 Potential of wastewater reuse in HCMC in 2025 16

Table 2-3 Water demand for expected WSI of HCMC 17

Table 3-1 Urban land cover change as the result from reomote sensing data 28

Table 3-2 Precipitation in HCMC in the future 30

Table 3-3 Sources for pollutants in collected rainwater and the problems when using it for other purposes 31

Table 3-4 the acceptable rainwater for different purposes 31

Table 3-5 Case study in Illinois, USA with economic benefits from using LID 31

Table 3-6 Water tariff in HCMC from 2013 to 2018 31

Table 4-1: Registered residents in HCMC from 2009 to 2034 31

Table 4-2 Population in HCMC from 2009 to 2034 31

Table 4-3 Average volume of water in 2010, 2020 and 2030 in HCMC 31

Table 4-4 the demand of industry use in HCMC 31

Table 4-5 Water demand for HCMC in the future 31

Table 4-6 Precipitation in HCMC in 2009, 2050 and 2100 31

Table 4-7 Proposed land use of HCMC in 2025 31

Table 4-8 Land use in Thu Thiem new urban area 31

Table 4-9 Predicted saving water tariff through using rainwater in the future 31

Table 8-1 Proposed land use in HCMC Master plan in 2025 31

Table 8-2 Net building coverage ratio 31

Table 8-3 Net building coverage ratio for apartments depends on lot areas and building height 31

Table 8-4 Maximum net building coverage ratio of mixed use buildings 31

Table 8-5 Predicted saving water tariff through using rainwater in the future 31

Table 8-6 Net present value for the investment of the tank in household 31

Vietnam has many rivers, lakes and canals with about 830 billion cubic meters fromsurface water, including 310 billion cubic meters collected from rainfall in this country.However, Vietnam is still a country with water shortages because the sources of water inVietnam are not sustainable The percentage of water from rainfall in the country is 37 %while 63% is from other water sources (upstream from other countries) The total watervolume for water surface and ground water in Vietnam is about 4.400m3 per capita peryear (while in the rest of the world it is 7.400m3 per capita per year) (Loan, 2005)

Ho Chi Minh City (HCMC) is the most developed city in Vietnam It is also the biggest citywith an area of 2,095 km2 located in the south eastern region of Vietnam This city hasthe highest population in the country, about 8,043,100 residents in 2014 The populationhas been increasing very quickly With rapid population increase, the demand for cleanwater is growing As a result, this city is facing the risk of illegal exploitation ofgroundwater, pollution of water and lacking of clean water for all its residents Therefore,there is an urgent need to find an alternative water source with rainwater being one suchsource

Thu Thiem is a new urban area in District 2, HCMC It is located on the East of SaigonRiver, opposite to District 1 and is the case study for this research This place is underconstruction

Figure 1-1 Aerial view of Thu Thiem area

Source: by the author

Currently, there are only few high – rise building constructed in this area and a villagenear the river banks The main roads in Thu Thiem area has finished The leveling istaking place in this place (See Appendix K) In new buildings, there is no rainwaterharvesting system

 Thu Thiem Master Plan of Sasaki Associates, Inc.

As the Master plan of Sasaki Associates, Inc (Sasaki), Thu Thiem peninsula will bedevelop as a dynamic mixed-use urban district comprised of housing, commercial, office,cultural, institutional, and open space uses Total area of this area about 737 hectareswith population proposed 130,000 permanent residents and 350,000 working people perday The land-use standard is 55 to 60 square meter per person Total floor area is over 6million square meter with average FAR from 4.0 to 4.5 (Sasaki, 2005)

Thu Thiem is divided into 5 Key Areas: Core Area, North Residential Area, East/westboulevard Mixed-Use, Eastern Residential and Southern Wetlands: The idea is this areahas delta research center, community gardens, and botanical garden, with commercialuse The ecological restoration zone is established and focused on mangrove restoration.The key concepts of Thu Thiem new urban area project are:

- Connect the District to the River

- Link Thu Thiem to Historic City Center and District 2

- Balance Development with Open Space

- Promote Density and a Compact Urban Form

- Insure Flexibility and Feasibility to Accommodate Growth and Change (Sasaki,2005)

Figure 1-2 Master plan of Thu Thiem new urban area

Source: (Sasaki, 2005)

The master plan is projected to construct for 20 years The phasing strategy assumes a20-year planning horizon, which is appropriate for such long term planning, including 4major phases Phase 1 planned in the time from 2005 to 2010 with the land area of 350hectares including a major portion of the Core Area and the entire Eastern Residentialarea Phase 2 includes the period of time from 2010 to 2015 This phase concentrate oncompleting Core Area and East/West Boulevard neighborhoods with the land area of 180hectares Phase 3 will construct from 2015 to 2020 for 87 hectares with other related

will be implemented in 2020 to 2025 to develop 120 ha of land area By this time, thenorth side of Thu Thiem has been transformed Development parcels in the southernwetlands are completed, as is the important bridge connection south to District 7.(Sasaki, 2005)

Ho Chi Minh City including Thu Thiem new urban area has a tropical wet and dry climate,with an average humidity of 75%. There are two seasons in a year: the wet season whichstarts from May and ends in November while the dry season is from late December tolate April The annual precipitation is about 2000 mm (in 2010) and there are about 150rainy days per year The temperature fluctuates from 28 - 40°C The hottest month isoften in April and the coldest month is in late December to early January (Office, 2012)With the advantages of being located in the tropical monsoon zone with high amount ofrain, rainwater can be an alternative source for water supply in HCMC as well as ThuThiem new urban area In many developed countries, rainwater has been harvested andtreated for use as potable water

“Rainwater harvesting (RWH) is an ancient technique enjoying a revival in popularity due to the inherent quality of rainwater and interest in reducing consumption of treated water.” RWH hasbenefits such as reduces flow to storm water drains and also reduces floods in the city;provides a water sources when the surfaces water is polluted and the ground water isunavailable and the costs is only for collection and use (Krishna, 2005)

If we reuse rainwater as one of the water supply source, this can reduce flooding inHCMC as well as the water stress for the water supply system There is also the need forcreating rainwater storage or pervious surfaces for rainwater runoff in the near future toreduce the flooding in inner city

In recent years, after having understood the benefits and issues of rainwater control,scientific researchers and environment engineers have developed many projects andstudies in the field of rainwater harvesting and reusing The aim is to evaluate thepotential and the effective way of using rainwater as an alternative source of watersupply

The possible usage for rainwater is through creating a rainwater utilization system whichharvests rainwater from roofs for sanitary flushing, irrigation and fire – fighting On largescale, storages, wetlands or dams can be constructed for water storage which can beused by industries during the dry season The impervious surfaces such as roads orparking lots could be replaced with semi-permeable surfaces to allow groundwater todischarge By implementing rainwater management in HCMC, flood conditions and watershortages can be alleviated The main purpose is to assist the natural water cycle anddevelop a sustainable water system

Ho Chi Minh City is suffering from many water problems The reasons are due to theincrease in population with the growing of new industries, economy activities andbuildings This has led to the increasing of water demand and waste water as well aspollution and climate change impacts to the natural environment

HCMC is suffering from pollution on surface water The quality of surface water is alluvialand salinity The main water supply sources of this city are from surface water intake ontwo (2) main rivers: the Saigon River and the Dong Nai River The amount of suspendedsediment in the water of Mekong River (upstream of the Dong Nai River) flowing to thesea is nearly 100 million tons to Phnom Penh The amount of alluvial will decrease thecapacity of irrigation system and storages, which can increase the cost for watertreatment Salinity is the other factor affecting water quality in exploiting groundwater.(Loan, 2005)

There is also the shortage of clean water for households in HCMC According to SaigonWater Supply Corporation (SAWACO), in 2013, only 89% households in HCMC can accessdrinkable water However, the quality of this water still does not meet the standard ofMinistry of Health about potable water (QCVN 01:2009/BYT - National technicalregulation on drinking water quality) because of the old pipeline system The physicalleakage of water supply in the system was about 34% in 2013 (SAWACO, 2014) and isstill one of the water problems in HCMC

Last but not least, the development of built-up areas also cause flooding andgroundwater pollution Unplanned or illegal constructions with buildings blocked the flow

of water in drainage canals or sewers Together with land use changes from lakes tobuildings or to roads which cause the development of impervious surfaces, these actionsreduce the capacity of water runoff During the rainy seasons, about 30% of urbancenters suffer from inundation caused by heavy rains The duration of these inundationsoften lasts from 1 to 12 hours The storm water drainage system has been maintainedbut after a few years, some areas still get inundated again (AGENCY, March 2011).There are approximate 100 flooding points in HCMC causing by heavy rain (see AppendixA)

Currently, rainwater harvesting and recycling techniques are not implemented in HCMC.Only some suburban districts use rainwater because these districts have no access to thecity water network In most areas of HCMC, rainwater is directed to the sewage systemand released into the rivers The storm water is collected by the drainage network andtreated together with waste water in water treatment plants Rainwater is less pollutedthan wastewater It is such a waste of resources because rainwater treatment is mucheasier and cheaper than waste water treatment They should be separated

Meanwhile, HCMC's water supply from the central water treatment plants, through a 50years old network system that is often leaking, reduces the efficiency of water supply.Moreover, rainwater is also not efficiently controlled in HCMC Due to the climatechanges, precipitation during the last 50 years is increasing Together with the new built-

up development areas with impervious surfaces, storm water has an effect on the flow ofground water, causing serious flooding in HCMC during the past 10 years Rainwatercannot go through the pavement and the drainage system cannot adapt to long rainingperiods In addition, most water treatment plants are exposed to regular and severeflooding in HCMC, especially in the north (Bank, 2010)

With these problems, there is the need to find a place for applying rainwater recycling.Thu Thiem is located in important place which rounded by the main Saigon river ofHCMC This is the sensitive position, if the development of land use is not efficiently, itcan effect to the water level of this river causing flooding or pollution in the whole city It

is predicted to be one of the most flooding areas of HCMC in next 50 years

As recommendation of Department of Urban Planning and Architecture (DPA) for masterplan of Sasaki, water demand from residents has been increased from 150 to 250 litersper person per day and demand from workers has increased from 150 to 350 liters perperson per day This suggested demand is higher than the standard demand of Ministry

of Construction (TCXDVN – 33 – 2006) with 165 liter/ca/day in 2010 and 200 liter/ca/day

in 2020 It needs to supply more water and rainwater is one of the choice to apply in thisarea

Thu Thiem new urban area is in the progress of construction To apply new technologysystems in this area, it might avoid the demolished costs The recycling rainwater in thisarea is one of solutions to reduce flood, increase water supply as well as to gain thecriteria of green buildings

- What is the impact on rainwater in terms of quality and quantity?

- How much potential rainwater can be used in the future?

- How to apply rainwater recycling in HCMC context?

The aim of these questions is to determine the application of rainwater harvesting andrecycling for domestic water or even industry water in HCMC This research studiesshows the potential of collected rainwater to be reuse as supply water and assess thefactors affecting the quality and quantity of rainfall and storm water After which, thesolution is treated as a case study for the Thu Thiem area – a new urban project underconstruction in HCMC

The goals are achieved through answering the questions of how much rainwater isrequired and how this would impact rainwater recycling in HCMC, specifically in the ThuThiem new urban area In order to reach these goals, the following objectives would be:

- To analyze the urban land development, existing technical infrastructure,architectural environment, natural environment, policy for rainwater reuse, thecitizen behaviors and attitudes towards reusing rainwater

- To determine the amount of rainwater that can be used instead of relying on thecity supply water network

- To set up criteria of rainwater harvesting in buildings (roof harvesting, storagetank and on-site water treatment system for groups of buildings) and in urbanlandscape (reservoir, permeable surfaces, etc.) in the context for HCMC

The hypothesis of this study is that rainwater can be a good alternative water resourcefor the supply of water in HCMC

The final objectives of this research are mainly carried out by qualitative methodologies:

- Based on the climate, economic and social data statistic from other scholars andfrom the statistic office to anticipate the trend of rainfall and water consumption inthe future, the paper has a closer look on the variety of seasonal rainfall, the waterconsumption at small scale and give an overview of rainwater recycling at largescale

- Reviewing the literature and secondary data through internet and library researchand project documents The observation of the existing urban planning of ThuThiem urban area and the analysis of the land use development, drainageinfrastructure of the master plan of Sasaki Associates, Inc (USA) is given in thisresearch The analysis of hazards released from local materials (brick, metal roof,asphalt road, etc.) is based on studies from researchers, which affects the quality

of rainwater

- Data calculation is followed the Vietnamese standard (TCXDVN) about waterconsumption and predicted potential rainfall in 2025 to generate the results ofpotential collected rainwater The scenario planning

- To determine the ability of recycling rainwater, two approaches are cost – benefitanalysis and SWOT analysis are chosen Cost-benefit analysis is the mostappropriate method to deciding whether to spend money on the investment to therecycling rainwater systems in the whole city as well as Thu Thiem area Itinvolves first figuring the cost of initial investment and then projecting the value ofthe benefits in economy, environment and society that it will provide The cost ofrainwater harvesting system for one household is compared with the gainedbenefits to determine the construction of recycling rainwater However, this CBAmethods does not provide an overview about recycling rainwater in the whole citywith external aspects The use of SWOT analysis (Strength, Weak, Opportunitiesand Threats analysis) for the case study area and for the whole city is to evaluatethe situation as well as the possible solutions The combination of two methodsprovide the overview of application of using rainwater in this city

1.5 Organization of the Study

This research is to be structured into 7 chapters

The first chapter is the “Introduction” which introduces the general information of thisthesis: the brief information about Vietnam, HCMC and Thu Thiem new urban area, thereasons for choosing this topic and choosing Thu Thiem as a case study, the problemsthat HCMC is facing, the aims of this topic and the methodology to research the topic Chapter 2 is the “Current situation analysis” that summarizes the population rate, the

water usage in HCMC, and the water demand with the growing population Therefore, there is the comparison among different water resources for residents in HCMC, to bring

out the advantages and disadvantages of using rainwater in the current conditions Literature will be reviewed in chapter 3, “Literature Review” The theories of recyclingrainwater, urban planning with water sensitive urban water and low impact developmentprogram will be concerned in this part In this chapter, the secondary data from thestatistics and other studies or reports from other scholars are analyzed This willinvestigate the factors causing the change in the quality as well as the quantity ofrainwater These impact factors that affecting rainwater quality such as the change ofland use, the development of impervious surfaces and the climate change will bediscussed

In chapter 4, “Results”, there is the anticipation for water demand in the future and the

determination of water resources to get sustainable water supply in future Then, thepotential of rainwater recycling is to study and calculate the amount of rainfall based onstatistics and data given by the statistic office This chapter shows the benefits fromusing rainwater in the future, how much volume of water can be gained and how much itwould cost

Chapter 5, “Discussion”, there is the assessment and recommendation for the changing

of urban and architecture materials as well as the architecture design based on theunderstanding of these impact factors Costs benefits analysis will be investigated todecide whether or not for the rainwater harvesting system in HCMC and Thu Thiem area.Then the SWOT analysis for HCMC and Thu Thiem new urban area is provided toconsolidate the benefits of recycling rainwater

The solution is given in chapter 6, based on the Water Sensitive Urban Design and Low Impact Development program This will illustrate the criteria and the design for rainwater

harvesting and recycling Some units of this area are developed based on the existingmaster plan project of Sasaki The urban design drawings would also serve to illustratethe ideas of using rainwater for this area There are the typical rainwater harvestingsystem, the scheme of rainwater drainage system and the typical details for permeablesurfaces that allow rainwater to flow through

Finally chapter 7 draws a conclusion to this research In this conclusion, an assessment

of a feasibility of this technique would be developed for the entire city

2.Current Situation

This chapter gives a brief information on the water supply, sanitation, waste water anddrainage in HCMC in recent years It also discuss about the current and the future waterstress index in the planning of HCMC Department of Urban Planning and Architecture(DPA) This index illustrates the imbalance between the water demand and the wateravailability for meeting consumption needs Water quality in HCMC is an important issuebut the concern for water demand is also very important in determining the balancebetween water supply and demand in the present and in the future

The objective of this chapter is to study the sustainable availability of water supply inHCMC After which, an analysis of water supply sources for HCMC is provided Theinvestigation of the demand and supply will point out the advantages and disadvantages

of water resources in HCMC Finally, the evaluation of using rainwater is given in thischapter too

The main water sources for HCMC are from the Saigon River and the Dong Nai Riverwhile surface water provides 2,120,000 m3/ day of water to HCMC (Bui Xuan Thanh,Nguyen Phuoc Dan, 2012) The development of industrial zones in HCMC near theserivers causes water pollution According to the Saigon Water Supply Corporation(SAWACO), the authorities of HCMC consider relocating the water intake from the SaigonRiver to the Dau Tieng Reservoir in the Tay Ninh Province There are two (2) large watertreatment plants (WTP) in HCMC managed by SAWACO: the Thu Duc WTP and the TanHiep WTP The Thu Duc WTP, known as the first WTP, was established since 1966 takingraw water from the Dong Nai River at Hoa An for the water supply to this city After anupgrade completion in 2002, the Thu Duc WTP can produce a capacity of 750,000 m3 perday The Tan Hiep WTP takes the raw water from the Saigon River at Hoa Phu andproduces a capacity of 300,000 m3 per day

The new WTPs are financed by private investors An additional Thu Duc WTP wascompleted under the management of the Thu Duc Water BOO (Built-Operate-Own)Company which has the production capacity of 300,000 m3 per day The Kenh Dong WTPfinanced by the Kenh Dong Joint Stock Water Supply Company has a production capacity

of 200,000 m3 per day This WTP is under construction and will take raw water from theDau Tieng Reservoir in Tay Ninh Province Clean water produced at this WTP will servethe northwest of Ho Chi Minh City and the bulk water supply to SAWACO

HCMC also uses ground water for water supply Ground water exploitation is around600,000m3/day while the sustainable amount of ground water exploitation is about500,000 to 800,000m3/ day (in 2005) The ground water is under the threats of saltwater intrusion, water table drawdown and contamination that have already beenmentioned Therefore, urban water supply from ground water sources is limited in Ho ChiMinh City (AGENCY, March 2011)

HCMC has 24 districts including 19 urban districts: District 1 to District 12, Binh Thanh,Thu Duc, Tan Binh, Binh Tan, Go Vap, Tan Phu, Phu Nhuan district and 5 rural districts(outer city urbanization) which are Hoc Mon, Binh Chanh, Can Gio, Nha Be and Cu Chidistrict Most urban districts are using surface water which are treated by the watertreatment plants and a small percentage of water from wells

Some districts such as District 9, District 12 and the Thu Duc district mainly uses waterfrom wells and only use a very small percentage of water from the city network system.Generally, all suburban districts mainly use well water and only use a very smallpercentage of water from the city network system

The table below shows the distribution of population and water sources usage for the 24districts in HCMC

Districts (a) Population(b) Water sources (%)

Urban

districts 6.060.202 Piped system(c) Well water (

c) Treatedsurfacewater (c)

(c): (Office, 2012) and (DONRE, November 2013)

The access to clean water in HCMC is still a problem Not all citizen of HCMC can access

to clean water According to the report of SAWACO in 2014, the access to clean watersources of the city is about 89% For the urban districts, the percentage of clean waterusage is 100 % for district 1, district 3, district 4, district 5, district 6, district 8, district

10, and district 11 and the Nha Be district For the suburban districts, the water supplyfrom city water distribution network is not enough For example, the percentage ofhouseholds in District 12 accessing clean water is 32.45%, in District 9 is 79%, while inthe Thu Duc district it is 87% and in the Hoc Mon district, it is less than 10% This meansthat 11% of the residents are not using clean water from city distribution network

The leakages in the water distribution system in 2014 is 34% As per the SAWACO report,this number would be reduced in the year of 2015, 2020 and 2025 to 32%, 28% and 25%respectively For the next 10 years, these leakages would not be able to be eliminatedwhich is a waste for the economic development

According to the Decree No.03-2013/NQ-HDND of HCMC People’s Committee in 2013regarding the socio-economic development of HCMC in 2020 and the prediction for 2025,the water supply from water surfaces for HCMC in 2015 would be 2.840.000m3/ day and

night while in 2020 it would be 3.100.000m3/ day and night and finally, in 2025 it would

be 3.700.000m3/ day and night As for ground water exploitation, the water supply in

2015 would be 330.000m3/ day and night while in 2020, it would be 220.000m3/ day andnight Ground water exploitation is to cease in 2025 Recycling of waste water oralternative water sources are to be looked into instead of ground water exploitation forthe future

Ho Chi Minh City has many alleys which has households with septic tanks that cannot beconnected to the public sewer networks This leads to waste water infiltration into theground, affecting the groundwater quality Also, some households flush water or pourtoilet waste water directly into the public sewer system without any preliminarytreatment That causes odor in the dry seasons as well as polluting the ground withsedimentation

Moreover, sanitary waste trucks which assist households to empty their septic tankscould hardly find a customer per day The Urban Drainage Corporation (UDC) has beenbuilding main interceptors for collecting wastewater and carrying it out to WWTPs

The main reasons of less frequency in removing sludge from septic tank are:

- The septic tanks are not designed to facilitate this operation The septic tanks areoften built at the bottom of the land plot This suggests that the owners do notintend to participate in such operations very often

- The sanitary waste trucks are not available (Bank 2006)

With the physical leakages in the public network, the soil and groundwater has beenpolluted by infiltrating water from septic tanks

The development of urban water supply systems has been increasing the waterconsumption per capita in urban areas Resulting from the increase of water use, wastewater is also increasing and causing environmental pollution As per the report of AsianDevelopment Bank (ADB), there is less than 10% of urban wastewater being treated(250,000 m3/day, out of 3 million m3/day), although the need of waste water treatment

is the government priority (in 2008)

Serious environmental degradation and health concerns are caused by water pollutionfrom untreated domestic waste water, unregulated discharge of industrial and hospitalwaste water (AGENCY, March 2011)

The table below shows the 2025 prediction for waste water recyclying uses

Using in urban

Irrigating for golf grass and sport centers 19.000

Lakes for entertainment

Recharge canal water inner cityTable 2-2 Potential of wastewater reuse in HCMC in 2025

Source (DONRE, November 2013)

Among those purposes of reusing waste water, water recycling for domestic andirrigation had a large percentage for reducing the WSI (Water Stress Index) In 2020, thepotential of recycling waste water for industry is predicted to be 160,000m3/ day In thecase of HCMC, authorities have policies to enforce the recycling of waste water, leading

to a demand of 1 million cubic meter of waste water per day (Office, 2012)

Regarding drainage system, HCMC has about 1,000 kilometres of existing drainage –including streams, canals and closed sewers These drainages are conduit for rainwaterand waste water Most of them existed from the 1870s during the colonial period,constructed by the French From the 1950s to 1975, the Americans improved thesedrainage system although not regularly

Built during the colonial period, most of these sewers were concrete, some constructedwith brick and masonry Some of these sewers now need to be repaired because theyhave collapsed due to high volume monsoon rains Moreover, the system was designedfor a population of 1.5 millions Now, the system is overloadeded because the populationhas now reached 8,043 millions in 2014 (only registered residents)

The existing drainage network is estimated to handle 650,000 m3 of water per day Mostunderground sewers flows to canals before discharging into the Saigon River With rapiddevelopment of built-up areas along the canals and the solid waste obstructing waterflows, the drainage system can not adapt to the new water volume Therefore, duringrainy seasons, floodings often happen in many areas of HCMC (U.S., n.d.)

“Water stress" is a condition where an imbalance occurs between the waterdemand/need and the water availability consumed for meeting that demand/need(UNESCO, 2009) Determination of water stress in an area will be determined by using anindex that is called the water stress Index (WSI)

WSI < 0.2: No Water Stress Area

0.2 ≤ WSI < 0.3: Low Water Stress Area

0.3 ≤ WSI < 0.4: Medium Water Stress Area

0.4 ≤ WSI < 0.5: High Water Stress Area

WSI ≥ 0.5: Very High Water Stress Area” (Ali, n.d.)

According to the Department of Planning and Architecture (DPA) of HCMC, 2007, theRevised Master Plan on the Construction in HCMC up to 2025, is to reduce the waterstress index (WSI) from 23% (0.23 – low water stress area) to 10% (0.1 – no water stressarea) in 2025, while requiring to supply 2.3 million m3 per day It means that thegovernment should have a strategy for protecting the water sources such as restrictingthe exploitation of fresh water, increasing water storage in dry seasons especiallystorage of rainwater and recycling waste water DPA (2007) reported that the discharge

of municipal waste water in HCMC in 2005, 2010 and 2025 were 1.5, 2.5 and above 3.0million m3/d respectively

The table below shows the water demand to meet the expected WSI of HCMC

Discharge of municipal wastewater in

3/day 2.200.00

0 0 1.300.00 400.000 Table 2-3 Water demand for expected WSI of HCMC

Source: (DONRE, November 2013)

Regarding the water sources to reduce the WSI, (N.P.Dan, et al., December 2011) saidthat “High rainfall in HCMC is a good option for an alternative fresh water source.However, collection, harvesting and use of rainwater may have drawbacks as follows: (i) High investment costs and large area for rainwater harvesting and storage; (ii) significant dependence on rainfall resulting in low reliability in terms of sufficientwater supply

In comparison with the above options, it is considered waste water recycling as thefeasible option for HCMC, the largest and most crowded city located downstream of theDong Nai river basin “

(N.P.Dan, et al., December 2011)

Thus, rainwater can be a potential supply resource when the problems of large scaleinvestment and storage for rainfall arises during the different months

The main water supply in HCMC is from surface water However, the quality of surfacewater generally does not meet the acceptable standard of the Ministry of Health (QCVN01:2009/BYT - National technical regulation on drinking water quality) Results from the

10 stations monitoring the water quality of the canals and rivers in HCMC indicated thatthe water in the canals is heavily polluted and need to be treated There are also 22monitoring stations measuring the river quality of the Saigon and the Dong Nai rivers –the 2 main rivers of HCMC Results at the end of 2012 indicated that 7 stations have badquality results, one station had quality suitable only for water transportation, 7 stationsgave results of quality suitable only for irrigation use or equivalent purposes; theremaining 7 stations have results of water quality that could be used for domestic butstill requiring treatment (see Appendix B)

Moreover, due to the effects by climate change, sea-level rises lead to salt waterpenetration during dry season It is estimated that for the entire Mekong Delta, saltwater intrusion could reach 60 to 70 km inland and inundate 15,000-20,000 km2 withjust 1 m of sea-level rise Salt water penetration will lead to the salinization of groundand surface waters which will endanger Ho Chi Minh’s water supply and the millions ofresidents (Fund, 2009)

Ho Chi Minh City is supplied by water from many sources: surface water, rainwater,brackish water and reclaimed water However, water is mainly used from the surfacewater of the Dong Nai and the Saigon rivers The table below shows the comparisonamong these water resources followed by the SWOT analysis of using rain water for thiscity

The table below is the analysis from Institute of Global Environment to summarize andcompare the water supply sources in HCMC

Item Surface water Rain water Brackish

water Reclaimed water

1.56m3/day from Saigon River and

Abundant, about 4.7 million m3

Rainfall ranges from 1,800 to 2,000 mm/year,

Abundant, especially in the

coastal zone (District 7 and

The current wastewater (WW) quantity:

• Domestic WW: 1,100,000

6 million m3/day from Dong Nai River.

80 –85% from June-August Can Gio). m3/day of which30,000m3/day is

treated

• Industrial WW: 32.600 m3/day

of which 15,100 m3/day is

treatedAbove 2 million m3/day in 2020

Currently, thebrackish water is only used for aquaculture (shrimp andfish farms)

Easy (but only in

6 months of rainyseason per year)

Easy (full year

in coastal zone such as District 7 and Can Gio)

Easy to collect the effluent fromthe centralized wastewater treatment plants

Stability Good Weak to medium

depending on the rainfall

2 Quality

Safety Good for

conventionaltreatment technology

Good for conventionaltreatment technology

Good for desalination technology

Weak to medium, depending on operation and maintenance of the advanced wastewater treatment system, skill of operators, etc

Stability Medium,

depending on seasons and pollutantsources

medium, depending on variation of raw wastewater

pH, SS, pathogens Pathogens, SS, high

salinity

biodegradable components, COD, trace organics, heavy metals,

Non-pathogens, color

A rain harvesting and storage system requires

Simple to medium depending on

Collection of effluents from the centralized

g condition, water

uptake capacity high investment cost and large

area

soil basementcondition, water uptake capacity

wastewater treatment plants

Flocculation filtration and disinfection

Coagulation-Conventional treatment:

Flocculation filtration and disinfection

Coagulation-Conventional treatment followed by desalination system

Advanced treatment such

as nutrient removal, SSremoval, COD removal,adsorption, advancedoxidation, etc

Use the available water distribution network

Separate water distribution networks for wastewater reuse High investment cost and

maintenance cost

+ SG River:

1,050,000 m3/day+ DN River: 2,250m3/day

The master plan for rainwater is not available yet

A project on desalinationsystem with capacity of5,000 m3/dayprepared by aprivate

company is under approval process

Reclaimed water

is not consideredyet in the

master plan of water supply in

2020 for HCM City

Unavailable for the

standards and laws

concerning use ofrain

water for water supply

Unavailable for the standards andlaws

concerning use of raw brackish water for water supply

Unavailable for the standards and laws concerning wastewater reuse

5 Risks

Subjective

risks Water quality may degrade due

to organic contaminants, pathogens, toxics

by industrial and domestic sources

Water quality may be

effected by acid rains,

excreta of animals living inthe roof, fields, etc

Water quality may degrade due to

organics, pathogens, toxin by industrial and domestic sources

Failure of operation and bad

to variation of industrial &

domestic wastewater

Table 2-12 Water supply sources in HCMC

Source: (Strategies, 2007)

Water supply for Thu Thiem new urban area will be provided from existing Thu DucWater Treatment plant In the existing condition, the water to Thu Thiem is limited.These existing mains provide water to the small settlement areas that lie to the northand east of the Thu Thiem site The southern wetland plays a pivoted role for the balance

of water in the Thu Thiem area as well as for the whole city

Regarding storm water drainage, there is presently no storm water management,municipal drainage system and no wastewater collection and treatment facilities in ThuThiem site The rainwater is collected and directed by the existing canals and drainagechannel Rainfall is typical of subtropical environment with 2 – 4 mm/ sec and less than

60 minutes Saigon River is around Thu Thiem peninsula, which is tidal twice a day The

100 year flooding will be 1.54 meters from the sea level Thus the HCMC Division ofWater Resource suggest that the design fill elevation should be 2.2 to 2.5 meters fromthe sea level

Regarding recycling rainwater in Thu Thiem new urban area, as the new master plan ofSasaki, rainwater has not used efficiently Storm water flows in network system to thewastewater treatment then treat together with wastewater (Sasaki, 2005) (Theinfrastructure plans see Appendix I)

In Thu Thiem new urban area, there is also no strategy on how to improve the water quality and water pollution (e.g floating trash/dirt from other districts) (EDAW, 2007) It suffers the same water quality with HCMC and will be in the shortage of water condition

in the future

3.Literature review

‘Urban planning is a technical and political process concerned with the use of land anddesign of the urban environment, including air and water and infrastructure passing intoand out of urban areas such as transportation and distribution networks.’ (Wikipedia,2014)

Water is an important part in urban planning, especially for these cities rounded by therivers If the urban planning does not concern properly about water, there may causesome problems like floods Therefore, design spaces for water is the most important rule

It does not mean that the construction on the lower level land is not allowed Becausethe human psychology likes living near water Moreover, the urban design needs tobalance the environment aspect and social aspect In urbanization we need to considerabout spaces for water like ponds, rivers and channels Otherwise, HCMC will be inserious floodings like in Bangkok (Dung, 2012) The traditional strategies of urbandesign are the concentration on construction of infrastructure to solve the problemscaused by water However, it doesn’t work effectively The new trend of planning design

is saving space for water (Dung, 2009)

There are three principles for water urban planning design:

- The first rule is that in any case, not be allowed to create an overflow generated

by the project It can be done through the buffering space or by the regulationponds

- The second rule is that the spaces for water are allowed to extend to adapt theuncertainty of climate change

- The floods in vulnerable regions need to be solved by flexible solution, not onlydepending on the anti-floods projects is the third rule (Dung, 2012)

In detail, the water urban planning design should use these tools:

- Land use planning tool: developing the places where cause less local risks and not increasing the risks for the whole city The urban areas should not develop in the place have risky flooding potential There should be some solutions to avoid floods for those buildings that located in the flooding potential areas.

- Market tools: informs the flooding risks and uses the tax on properties so that the real estates market can adapt to flooding risks The investors should not construct the buildings in these flooding risky areas.

- Urban design tools: increase the water surfaces, natural landscape and green spaces to prevent flood and create beautiful view for the city (Dung, 2009)

Moreover, the overall and multidisciplinary approachs are the most effective approachfor urban planning design and management Not only city planners and water engineersbut also city authorities should collaborate on solving the rainwater problems in this city.Water resources management become one of the part in urban planning design (Dung,2009)

Spatial planning play a pivoted key because it instructs and reminds the communities ofthe flooding potential The development at the low level lands need to be restrict In case

of unavoidable situation, the requirement of reduced damage need to be investigated.(Dung, 2009)

In developed countries, they are implementing the programs to manage rainwater inurban design, such as Water Sensitive Urban Design program in Australia

For the sustainable development, there are lots of initiatives to manage urban water withkey principles: water conservation, integrated water cycle management, wasteminimization and environment protection

‘Water Sensitive Urban Design (WSUD) is the interdisciplinary cooperation of watermanagement, urban design, and landscape planning It considers all parts of the urbanwater cycle and combines the functionality of water management with principles ofurban design WSUD develops integrative strategies for ecological, economic, social, andcultural sustainability.’ (Hoyer, et al., 2011)

WSUD is the combination of demands: the demands of sustainable storm watermanagement and the demands of urban planning Its objective is to bring the urbanwater cycle closer to natural one WSUD concerns the management of whole watersystems such as potable water, non – potable water, recycling, storm water runoff,waterway health, and sewerage treatment However, it mostly considers with rainwater

management issues (Hoyer, et al., 2011)

There are 5 topics that WSUD is involved to:

- Water Sensitivity: the design should bring the urban water management closer to the natural water cycle by using the decentralized methods.

- Aesthetics: the design should create aesthetic benefits Besides, the design should harmonize the surrounding areas.

- Functionality: the design should adapt to the local basic conditions and the purpose of uses The maintenance requirements and the possibilities for adaptation to uncertain and changing basic conditions should be considered.

- Usability: the design should create places that can use for recreation and/or nature conservation purposes.

- Public perception and acceptance: the demands of the stakeholders should be given priority in

the planning process The costs in the planning process should be compared among other options (Hoyer, et al., 2011)

To meet the requirements of all the topics above, there needs to integrate these topics.Therefore WSUD solutions is integrative planning It means that there is the combination

of function, aesthetic and usage All should be planned be planned in interdisciplinary operation of urban planning, urban design, landscape architecture and water in order toimprove the public perception and acceptability of WSUD (Hoyer, et al., 2011)

Combination of the concept of rainwater harvesting and water urban planning designwith the climatic data, social and economic conditions will help to better judge theapplication of rainwater recycling in Ho Chi Minh City, especially in Thu Thiem new urban area The basic ideas of WSUD about water management in urban planning design is suitable for HCMC context which have numerous river systems WSUD is to be able to prevent the negative impacts fromstorm water in order to reduce the flooding as well as the water shortage condition inthis city Urban storm water treatment is an opportunities to be an alternative resource.This study concerns and applies WSUD in the district scale of Thu Thiem new urban area.There is also some limitations of the research because each area has its own conditions

to apply a new design The research gives the general assessment about rainwaterrecycling in the whole city, as well as chosen Thu Thiem new urban area as a case studyfor the water urban planning theories

‘Rainwater harvesting, collecting rainwater from impervious surfaces and storing it forlater use, is a technique that has been used for millennia It has not been widelyemployed in industrialized societies that rely primarily on centralized water distributionsystems, but with limited water resources and storm water pollution recognized asserious problems and the emergence of green building, the role that rainwaterharvesting can play for water supply is being reassessed ‘ (Kloss, 2008)

There are two main types of rainwater harvesting and conserving, which are the activeand the passive rainwater harvesting systems The active rainwater harvesting systems

(e.g., cisterns) have capacity of 4,000 - 4,000,000 liters, which capture runoff from roofs

or other suitable surfaces (e.g., terraces, walkways, grassed areas and with proper treatment, parking lots), provide water quality treatment, and use pumps or sufficienthead to supply water to a distribution system The passive systems are designed tocapture runoffs from roofs, which have typical capacity from 200 – 400 liters (EPA, 2013)

pre- Benefits from recycling and harvesting rainwater:

There are numerous potential benefits and advantages from rainwater harvesting as thefollowings:

- Rainwater harvesting systems can provide a source of free water – the only costswould be for storage, treatment and use, therefore it can save money in waterbills; it is also the water source if there is no other source or no connection to thepiped water;

- Rainwater is the natural soft water with pH neutral or slightly acidic, sodium – freethat suitable for people who is on low sodium diets;

- Rainwater augments or replaces limited quantities of groundwater to reduce thedemands on groundwater; rainwater’s quality is also good if groundwater quality isunacceptable and surely can use for landscape irrigation or for non-potable indooruses After appropriate treatment, rainwater provides safe water for humanconsumption and for cooling and air-conditioning plants as well as fire protection;

- Rainwater reduces storm water runoff and erosion in urban environments It alsoreduces non-point source pollution;

- Rainwater helps utilities in reducing peak demands in the summer and in delayingthe expansion of water treatment plants; (Krishna, 2003)

‘Rainwater harvesting also provides several additional benefits It can reduce scalingbuild-up in hot water heaters, plumbing, faucets, and showerheads Rainwater requiresless soap and detergent than most public water supplies because of its natural softness

In particular, use of rainwater can be valuable for the hotel industry, helping themreduce their use of municipal water supplies and the amount of detergents used for theirdaily laundry’ (Krishna, 2003) In addition, rainwater harvesting can reduce energyrequirements and carbon dioxide emissions, compared to conventional water supplytechnologies, due to reduced pumping in the plants At a broader level, because thedecentralized system harvests rainwater on site before it becomes dirty, it reduces theenergy required for water treatment and transportation and therefore decreases thecarbon dioxide production and the long-term social cost (Barron, 2009)

Regarding the rainwater harvesting system, there are also some small advantages:

- The construction of RWH systems is quite simple and the locals can be trained to build it The operation and maintenance at household level are controlled only by the family As such, this is

a good alternative to poor maintenance and monitoring of a centralized piped water supply This reduces cost for distribution system from the centralized piped supply to household The water is provided at the point of consumption

- Many kind of rainwater tanks are to suitable for local circumstances and budgets, such as the low – cost tanks made of Ferro cement, plastics or stone/bricks.

- Rainwater is not affected by local geology or topography The tanks can be built inthe roof, underground or ground.(Worm & Hattum, 2006)

 Disadvantages of rainwater harvesting and recycling:

Although there are many benefits for recycling rainwater, the implementation ofrecycling rainwater also have some disadvantages, such as high initial investment cost,usage and maintenance, the vulnerable quantity and quality, and the limitations ofstorage

The main disadvantages of recycling rainwater is its instability of rainfall It is not easy topredict how much rain will fall The unpredictable rainfall decreases the attractiveness ofthe recycling rainwater projects The size of these storages are also the problems to

determine It is hard to construct an optimal size with the unpredictable rainfall to avoidthe waste in construction or insufficient capacity (Worm & Hattum, 2006)

The initial cost is also one of the strongest factors that hinder the implementation ofrecycling rainwater in HCMC This cost can be recovered during the next 10 or 15 years.The payment for a project that have more intangible ecological benefits than tangibleeconomic benefits seem not to be feasible (Worm & Hattum, 2006)

In addition, one of the disadvantages of rainwater quality is its vulnerability Therainwater quality can get polluted easily by other pollutants There might be the animaldroppings, the seep chemical or algae in the storage To control, operate and maintainthe surfaces of a catchment area at large scale requires more costs Storage of rainwaterneeds to have regular maintenance otherwise it will be a breeding place for mosquitoes,algae and might also be the source of pathogens The collected water also needs to betreated before use Through long periods of time, the fee for the treatment andmaintenance of such storage facilities can become costly (Worm & Hattum, 2006)

The aim of rainwater storage is to allow rainwater to be used in the dry periods.However, evaporation under hot temperature can cause the storage tank, like ponds anddams, to lose a large amount of water This would limit the water supply in the dryseasons The amount of water is also limited by the size of the catchment areas or thestorage reservoir’ (Worm & Hattum, 2006)

Moreover, the lower water level of ponds or dams causes negative impacts to ecosystem

as well as to recreational landscape Natural fluctuations in water level (over both shortand long term) are essential to maintain habitat diversity and critical ecologicalfunctions Low level water affects quality water in the lake in case the long dry periodssuch as destroying the life of habitat diversity in the ponds and reduce the recreationalvalues for tourism (Kahl, n.d.)

Although these advantages can be overcome through proper design, ownership and byusing as much locally available material as possible to ensure sustainability (and costrecovery), it is not attractive to many household owner The involvement of the localprivate sector and local authorities can facilitate upscaling of RWH.’ (Worm & Hattum,2006)

3.3 Current rainfall situation in HCMC

‘The rainfall pattern over the year plays a key role in determining whether RWH cancompete with other water supply systems’ The rainwater harvesting is suitable when thedry season lasts for one to four months like the tropical climates If the rainfall is over50mm per month for at least half a year or minimum 300mm per year, there is theenvironmental feasibility of rainwater harvesting (Worm & Hattum, 2006)

Rainwater recycling can serve as an effective tool for storm water management and forwater supply There are some ways to recycle rainwater by collecting from roofs orstorage storm water before using as non–potable or potable water Many programs in theworld are encouraging rainwater recycling by rainwater harvesting to conserve potablewater, to protect the quality of the surface water and to reduce the risk of flooding

Ho Chi Minh City is located in the tropical savanna climate with high rainfall There is anenvironmental advantage to use rainwater Thus, the costs and benefits of usingrainwater at large scale and household scale is also analyzed in this chapter

In Ho Chi Minh City, there are many positive potentials for using rainwater in supportingthe city’s water supply system due to high volume of rainfall precipitation (Chi & Hoa2011) These potentials are affected in their process of evapotranspiration, infiltration,storm water run-off and reticulated sewer In urban land development, it needs to beevaluated to estimate the volume of collected rainwater in order to have an efficient way

to use this water (Goen, et al., 2008)

The average annual rainfall in HCMC is over 1500mm The data record indicated from

2005 to 2010, the annual precipitation fluctuated from 1700 to 2340 mm In 2007 theprecipitation was 2340mm while during the other years the precipitation was from 1700

to 2000 mm For the implementation of calculation, the mean annual rainwater based onrecent data is given as 1,978 mm This is quite a high rainfall in comparison with othercountries all over the world (WorldBank, 2014)

The chart below shows the annual precipitation in HCMC from 2005 to 2010

Figure 3-3 Annual precipitation in HCMC from 2005 to 2010

Source: (Office, 2012)

With regards to the monthly precipitation, there is a big difference in rainfall betweentwo seasons: the rainy season and the dry season It rains heavily from May to Octoberwith a precipitation over 150mm In the dry season from November to April, theprecipitation is under 100mm, with a minimum in January or February (Online, 2014) (seeAppendix C) From 1960 until 2008, the annual precipitation had increased by about110mm (from 1850 to 1960) On the average, the annual rainfall increases 2mm.However, the maximum daily rainfall had increased significantly in the period of 1970 to

2007 In detail, in the period of 1970 to 2007, the maximum daily rainfall was 92mmwhile in 2007 it was 109mm (Dang, 2012)

With regards to daily precipitation, the highest rainfall day occurs in September with theamount of 179mm per day whilst the lowest rainfall day is in February with about 38mm

as per the recorded data in 2008 (Technology, 2008)(see Appendix C)

The rainfall intensity is distributed unevenly in the year, including thunderstorm, heavyrain, light rain, moderate rains and drizzle (see Appendix C) The collected data describesthe typical weather at the Tan Son Nhat International Airport (Ho Chi Minh City, Vietnam)weather station over the course of an average year It is based on the historical recordsfrom 1983 to 2012 Earlier records are either unavailable or unreliable (WeatherSpark,2014) Most rains are thunderstorms which is 70% while the heavy rains is only 1% butthey do still causes serious consequences

To sum up, the total of rainwater amount in Ho Chi Minh city is quite high, as per thereport of the Vietnam – Korea conference about rainfall assessment, the results showthat

- Annual rainfall amount: 3.3 billion m3

- The highest monthly rainfall is in September: 0.5 billion m3

That is the potential water supply source that HCMC could used in the future If HCMCcan take advantage of the potential amount of rainwater to supply water, many waterrelated problems can be resolved.

In the scope of this paper, impact factors of rainwater recycling only focus on the threeaspects of sustainability theory: economic, social and environmental aspects They arethe type of development, catchment conditions, climate, users’ acceptance and theirincome, the rainwater policies and the refunding of financial investment

The most influential factor to quality and quantity of rainwater is the type ofdevelopment, particularly land use change and catchment conditions Land use changeleads to the change of surface materials which also causes the change of temperatureaffecting the quantity of rainwater through evaporation as well as causing pollution forthe quality of rainwater Meanwhile, another factor impacting on recycling rainwater isthe acceptance by the users Most people in some suburban districts still accept the use

of rainwater for their domestic water Not only should there be increased acceptance byusers using rainwater for domestic usage, the policies of the government or authoritiesmust also play an important role in further encouraging them to use rainwater

With regards to the economic aspect, the investment cost for rainwater storage andrecycling system plus the return are important points These things affect the quantityand quality of rainwater if they are not being controlled and maintained effectively orproperly Besides, the income of residents in HCMC the water tariff also takes intoaccount For instance, the water tariff for unregistered residents is quite high incomparison to their income This may influence the attitude of residents to decidewhether or not to use rainwater

 The effect of land use change to environment

Natural areas with open land and vegetation have been replaced by built – up areasthrough the urbanization in order to meet the living space requirements Thedevelopment of impervious land increases the temperature of these areas and alsocauses some negative influences to rainwater and storm water In short, built-up areaslike roads, roof houses, buildings, parking lots and so on reduces the evapotranspirationfrom 40% to 30% and increases the water runoff to nearly 5.5 times in comparison withnatural ground cover such as lawns, green spaces, or lawn parks This causes floods inbuilt-up areas during heavy rainfall Besides, the infiltration of rainwater into groundreduces from 25% to 10% in the shallow soil and from 25% to 5% in the deep soil.Pollutants also infiltrate into ground water (EPA, Feb 2003)

The urban development changes natural land with the growth of the impervious surfacesand creates unintended problems such as

- Removal of natural storage, retention, and recycling of precipitation

- Significant increases in overland runoff into surface waters

Figure 3-4 Relationship between impervious cover and surface runoff

Source: (EPA, Feb 2003)

One of the case studies is the urbanization in Seoul, Korea which showed that “thehydrological components, such as evapotranspiration, surface runoff and groundwaterrecharge, were highly dependent on changes to impervious areas From 1975 to 2005,the impervious areas doubled, resulting in a reduction in evapotranspiration of 29%, anincrease in surface runoff of 41% and a decrease in groundwater recharge of 74%.” (Lee,

et al., 2010)

Moreover, land use change with impervious cover increases the water runoff peak flowand volume while reduces the recharge of ground water Urban development can changethe stream flow, the stream direction which change the geometry and also changes thewater quality Besides, urbanization can affect aqua habitat (Commission, August 2001)From recent decades, the land use changes quickly in Ho Chi Minh City leading to manyproblems that affect evapotranspiration, infiltration and the quality of water, particularlycausing floods in many districts after heavy rainfall First of all, HCMC is located in avulnerable location of the Dong Nai and the Saigon rivers downstream that is easilyflooded by the tide In addition, HCMC has been expanding in the wrong direction.Instead of developing to the high land region in the West – Northern West, it hasdeveloped in the opposite direction (the East – Southern East direction) which is thelowlands These lowlands with appropriately 7.900km of canals and rivers were thedrainage area for the whole city because the water flows mainly from the North –Western North – Eastern North areas to the South – Eastern South – Western Southareas The lowlands occupied 61% of the total area With the expansion of the built – upareas, water storages and drainage areas shrank Together with the wrong developmentideology in the planning, HCMC is also suffering from the heavy flooding situation caused

by the rain and the tide

Land use change in HCMC, especially in South Saigon like the Binh Chanh district, district

7 and the Nha Be district, affected the temperature – one of the factors that altersevapotranspiration to the infrastructure and precipitation In the period of 17 years from

1989 to 2006, the built-up land in HCMC increased from about 7,300 ha to more than47,000 ha (about 22.47% of total area of HCMC) (Tran Thi Van, 2011)

As a result, the surface temperature had increased from 29.8o C in 1989 to 33.3 o C in

2006 In the 19 inner districts of HCMC, the average surface temperature rose up 0.26 o Cper year The highest temperature was in the industrial region, which fluctuated from 40 o

C until 45 o C In the residential regions, the average temperature was over 35 o C In

2006, the difference of average temperatures to these areas were 10 – 15 o C The

surface urban heat islands (SUHIs) in the city had an area of 28.000 ha in 2006, whichwas 24 times in comparison with their areas in 1986 The increase of impervious areas

on large scale increases the maximum temperature This is one of the reasons toaugment the number of heavy rains in HCMC lately (Tran Thi Van, 2011) Furthermore,the pervious surfaces have been changed into impervious surfaces which reduced theabsorbability from 50% to 13%, according to Dr Luu Duc Cuong

The change of land use had been recorded by the remote sensing from 1989 to 2006.The table below illustrates the change in that period

Table 3-4 Urban land cover change as the result from reomote sensing data

Source: (Tran Thi Van, 2011)

The result above was illustrated by the figures below:

Figure 3-5 Results of urban expansion in the Northern part of Ho Chi Minh City in 1989, 1989, 2002 and 2006 from remotely sensed data

Source: (Tran Thi Van, 2011)

Because of the increasing of built – up areas, it made the temperature warmer Thefigure below shows the change of temperature affected by the urban land from 1989 to2006

Figure 3-6 the change of temperature from 1989 to 2006

Source: (Tran Thi Van, 2011)

With regards to the infrastructure, the old drainage system cannot serve the new urbanareas because their capacity were designed and calculated for small areas Theconstruction of buildings in the wetlands such as South Saigon or Nha Be blocked thenatural water flows When it rains heavily, the water is obstructed by constructionmaterials and causes floods The floods by storm water have become more and moreserious As the assessment of Prof Le Huy Ba, “the more development of new urbanareas in South Saigon, Binh Chanh, District 7 or Nha Be, the more obstruction to the citydrainage system.”

Finally, with regards to rainwater quantity, the rainwater and water runoff has changed.The runoff has increased to 200% and the infiltration also reduces in shallow ground anddeep ground That makes the change in the rainfall quantity The predicted rainfall in

2050 would be reduced 7.2% - 8.1% in the dry season and increase to 6.8% in the rainyseason (ARUP, 2010)

The table below indicates the predicted annual rainfall in the future

Moreover, there has been the extreme rainfalls, which means that the annual volume ofwater does not increase, but the intensity of rainfall increases It means that there is

more rain in the rainy season and more droughts in dry season This makes the cityhaving more serious flooding The extreme rains may break the dam of hydropowerstorage in the upstream and leads to domino effects HCMC is flooded by billions cubicmeter of water from the height of 100m (Hung, 2008)

 Catchment conditions

Rainwater needs catchment places to store or to reduce water flows The catchmentsgive strong effect to rainwater recycling and have consequences to related issues.Therefore, the implementation of the HCMC master plan need to look into catchmentconditions

A long time ago, in the studies of HCMC, Nikkei Seikkei Ltd (Japan) suggested that newurban areas should be located in highlands and needed a regulating pond with capacity

of 180 – 200 m3 per hectare In the case of the buildings constructed in the lowlandssuch as Nha Be or Phu My Hung, there was a requirement of the large open space to bethe buffering region for flooding protection (Dang, 2012)

The other proposed master plans of HCMC by Colonel Coffyn, engineer Pugnaire or grouparchitects Le Van Lam also recommended that this city should not have developedindustries and urbanization to the South and the Southern West direction Nha Be, CanGio, district 7 and part of Binh Chanh district) because they are low level areas whichstored water in case of heavy rain or tide They were also the rainwater drainage areas

of Saigon Since HCMC slopes from the North to south, these areas should be constructedwith low storey houses or vernacular houses and should not be covered by impervioussurface so that water could be absorbed (Hoa, 2006)

The reason for the concept master plan like that is because when being established,Saigon (the former name of HCMC) was located on the high land of the Dong Nai andSaigon rivers where it was 3 meters higher than the average sea level However, with theexpansion to the wrong direction, now more than 60% of HCMC (about 120.000 ha) is1.5m lower than the average sea level

Currently, in the process of implementing the master plan for HCMC, the authorities didnot apply these suggestions above and filled most existing lakes and ponds as well ascontinued expanding to the Can Gio coastlines and to the lowlands in the South Thisgives negative effects to the waterways system HCMC has 700 canals, rivers and lakesand many of them are important drainage system According to the VietnamEnvironment and Sustainable Development Institute, the urbanization in the recent 14years from 1990 to 2004 in HCMC has caused the disappearance of 47 canals with a totalarea of 16,4ha, especially the filling up of the Binh Tien Lake which had 7,4ha – one ofthe biggest storage lake of HCMC Storage capacities of the canals and lakes in HCMCare reduced 10 times in 8 years from 2002 to 2009 when the impervious areas increased2.5 times The water storage areas have changed into new urban areas For example, theland fill to construct the Phu My Hung urban area reduced the storage capacity of Saigonabout by 10,000m3 The catchment areas of HCMC are decreasing due to the wrongdevelopment (Dang, 2012) From July 1996, the infrastructure work began in district 7.After more than 10 years, HCMC has had more flooding in the whole the city because ofthe obstructed storm water As per the statistic, in HCMC there are 163 inundation areasdistributing in 24 districts Districts 8 and 6 especially are facing heavy inundatedconditions (Dung, 2011)

Currently, there is no constructed wetland or regulation ponds to collect and recyclerainwater in HCMC According to the Steering Center of the Urban Flood Control ProgramHCMC, there is a strategy to construct 30 large regulation lakes in HCMC to reduce 30%

of flood conditions These lakes might regulate 10 million cubic meters of water in next

10 years (City, 2014) Therefore, the rainwater can be collected and stored by lakes orponds or regulation lakes Rainfall can be uneven during the year During the rainy

season from May to November, rainwater needs to be stored for uses during dry season

in order to decrease the floods and drought in HCMC

As a consequence, the change of the catchments has not only cause flooding in the city,but also the collapse of the soil surfaces due to the construction on unstable land and theover exploitation of groundwater Each year, the sinking of soil surfaces in urban HCMC isabout 15mm (Dang, 2012)

 Potential hazards from pollutants in collected rainwater

The quantity of rainwater is impacted by land use changes and catchment conditionswhile its quality is influence by the hazards released from material surfaces The change

of material surface leads to the pollution in quality of collected rainwater made by thehazards such as alkali metals, heavy metals and other trace elements or xenobioticorganic compounds

As for the quality of storm water, sediments from storm water retention ponds, roadsideswales and street sweeping need to be disposed of The rainwater is also impacted bypollutants and nutrient loads from materials which affects human health In urban areas,the materials of the surfaces and the reservoir should be considered with hazardidentification releasing from materials (Eva, et al., 2002).The harvesting of storm water isthe means of conserving a valuable water resource as well as reduction of impacts frompollutants and nutrient loads on the river system or the ecosystem Storm water brings agreat variety of pollutants, such as sediments, nutrients, trace metals and organiccompounds (H.Kadlec, et al., 2000) Studies have found that sediments in storm waterfrom commercial areas are more than non-commercial areas Besides, sediments fromstorm water retention ponds and swales are more polluted with heavy metal than naturalsoils Street sweeping have low level of heavy metal pollution because of their coarseparticle size These sediments from storm water need to be deposed of or treated.(J.Liebens, 2001)

Some examples of sources that potentially are contributing to the pollutant load incollected rainwater are metal roofs, bricks, paint and varnish, etc Rainwater is not onlyinfluenced by urban surfaces and urban traffic but also by the tank or storage of it Whenrainwater is collected then used for flushing toilet, laundry, outside washing ordischarges into the environment, the pollutants from material releases can causeallergies, infectious diseases or odors

The table below shows the sources for pollutants in collected rainwater and the problemswhen using it for other purposes

  Weld and joint

materials Washing of cars and windows Infectious diseases

  Rock and mineral

Source: (Eva, et al., 2002)

As per the table above, there are many sources that can pollute the collected rainwater.The more artificial material, the more pollution is created Even animal activities produceexcrements which also causes smell or taste to rainwater

In the context of HCMC, the percentage of impervious area is quite high, over 47,000hectares where most residents are living Most roads and streets surfaces are made ofasphalt Buildings are constructed by brick or concrete and covered by emulsion paint.Roofs are made of metal or tiled These materials may lead to hazards for human health.Therefore, we need to use materials and other thing to reduce the pollutants in collectedrainwater or we need to treat the water before using The collection system which should

be below the natural filter of soil and sand, can be easily treated

The report in the conference of Vietnam Institute of Meteorology, Hydrology and Climatechange, the quality of rainwater in HCMC is quite good The sources of water pollution inthe air including dust, the chemical compounds, bacteria and other compounds causingacid rain There is only a few of acid rain As the rainwater sample in 12 stations in HCMC

in 2010, the pH in rainwater is about 6.0 as the standard of rainwater quality Theconcentration of the ion Na+, stiffness, NO3-, NH4+, SO42-, Cl- is much lower than thestandard for potable water of Ministry of Health However, in Hoc Mon, Binh Chanh and

Cu Chi districts (suburban districts), the NH4+ exceeds the standard This NH4+ mightcome from the agricultural activities (Hieu, et al., 2013)

Collected rainwater is influenced by many aspects The poor residents living in suburbanwho cannot access piped water still store rainwater to use They need to treat rainwaterfor laundry and shower otherwise they will have negative health effects to their skin Thepollutants from collected rainwater caused rashes for the users when they used itwithout proper treatment

Therefore, the master plan needs to be concerned with the materials which are suitablefor human health, and not just for collecting rainwater, as well as for storm waterrecycling On large scale, if using rainwater as an alternative water source, the potentialhazard constituted is quite high It needs to have treatment requirements and needs tohave studies of rainwater quality in HCMC

These parts above mentioned about one aspect of sustainability - environmental aspect,which have many problems that give negative influences to rainwater recycling As forthe social aspect, the attitudes of residents and authorities are quite important torainwater recycling as an alternative water source In the scope of this research,rainwater used for domestic consumption is looked into

 Acceptance of using rainwater for domestic water

Water can use for households (domestic water), for industrial, for agriculture and forcommercial For domestic water, until now, the percentage of water usage in HCMC have

no statistic data Therefore, this research uses the data of the survey carried on in Hanoi.The water consumption in Hanoi shows that in a typical house, approximately 67.7% ofwater was used indoor: 18.6% for flushing toilet, 10.4% used for shower and sink, 16.2%used for laundry, 15.7% was used for cooking and 6.8% used for other purposes (Bao &Aramaki, 2012) Outside of the house, 32.3% was used for lawn and garden care

The pie charts below show the percentage of water consumption in typical household inHanoi – Vietnam

Figure 3-7 Percentage of water usage in households

Source: (Bao & Aramaki, 2012)

The table below shows the attitude for acceptance of using rainwater as potable source for domestic and commercial purposes

Ke

y A Acceptable P Possible N/R

Not recommend

Not applicable

  (rainwater)Domestic Rainwater(from roof

only)

Storm water (roof andground)Amenities/

based on the previous results from the survey in Hanoi It shows that rainwater without

treatment, can be used for washing vehicles or irrigation, which is 32.3% of the waterdemand per day Rainwater can be also use for flushing toilet and laundry, which have18.6% and 15.7% of water use respectively, and totally is 34.3% for indoor water uses

Besides, people are acceptable to use treated rainwater for bathroom and kitchen, bothoccupied 26.1% of water use.

Currently, rainwater is being used in some suburban districts of HCMC, such as Can gio,Nha Be, or District 7 because they cannot access to the piped water They prefer usingpiped water to rainwater or to treated storm water because of the hazards of pollutantsfrom materials As for stormwater without treatment, it is not easy to accept it for using.Stormwater should be collected by the drainage system and then treated in centralized

or decentralized water treatment plant If people can collect rainwater at home, theycould also treat this water before using it for shower or washing purposes

 Strategies and policies of reuse rainwater

Another factor that impacts rainwater recycling is regulations or strategies for rainwatermanagement In many developed countries such as Australia, United Kingdom, theUnited State or Singapore, there are lots of policies or programs about reusing rainwater

as an alternative water source For instance, in Australia, the implementation ofrainwater management is reinforced by policy Rainwater is harvested and used as acheaper supply water source They applied Water Sensitive Urban Design (WSUD)Program in Australia that aims to ensure the planning, design, construction andretrofitting of urbanized landscape which is more sensitive to the natural water cycle(CHEN, et al., 2008) This program is used in the process of constructing new urban area

to ensure the planning design meet water sensitive requirements

Another example is the Low Impact Development (LID) approach to manage storm water

as close to its source as possible The principle of LID is “minimizing effectiveimperviousness to treat storm water as a resource rather than a waste product” (EPA,2014) Some case studies proved that application of LID into storm water managementcan save a big amount of money For example, in Naperville, Illinois, USA, the application

of LID brought economic benefits as illustrated in the table below

Construction Item Cost of

ConventionalDevelopment

Cost When UsingLID Practices Dollars Saved withLID