Evaluating runoff generation and water quality at a small forested catchment study case luot mountain at vfu in xuan mai town, hanoi capital, vietnam

ABSTRACT To evaluate runoff generation and water quality at a small forested catchment, we conducted and monitoring station, collected da from weather station and examined some water qua

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

VIETNAM FORESTRY UNIVERSITY

Faculty: Forest Resources and Environmental Management

Student: Vu Duong Ly Student ID:0954011529

Class: K55 Natural Resources Management Course: 2010 – 2014

Advanced Education Program

Developed in Collaboration with Colorado State University, USA

Supervisor: Dr Bui Xuan Dung

Hanoi, November 2014

ACKNOWLEDGEMENT

I would like to express my sincere gratitude to Dr Dung and Prof: Lee Mac Donald providing continuous encouragement and enthusiastic support during the research work in I greatly appreciated the help provided for by the weather station and laboratory work at Vietnam Forestry University, and would especially like to thank Ms Diem, Mr Le who helped me directly

TABLE CONTENT

ABSTRACT 1

I INTRODUCTION 2

II OVERVIEW OF THE PREVIOUS RESEARCH ISSUES 4

2.1 Overview 4

2.2 Limitation of the previous studies 5

III OBJECTIVE, SCOPE, CONTENT OF THE STUDY 6

3.1 Objective 6

3.2 Scope 6

3.3 Contents Error! Bookmark not defined IV STUDY SITE AND METHOD 7

4.1 Study site 7

4.2 Method 8

4.2.1 Rainfall monitoring 8

4.2.2 Catchment runoff monitoring 8

4.2.3 Observating water quality of catchment runoff 8

V RESULT AND DISCUSSION 13

5.1 Characteristic of runoff generation 13

5.2 Runoff component 16

5.3 Water quality and characteristic of catchment 19

VI CONCLUSION 24

REFERENCES 25

LIST OF TABLE

Table 1: Climate- Hydrology indicator at Xuan Mai (Ba Vi weather station) 7 Table 2: Physical and chemical materials 9 Table 3: Parameters index 23

LIST OF FIGURES

Figure 1.Location of study site and rainfall, runoff monitoring 6

Figure 2 Runoff generation in forested headwater catchment over time 13

Figure 3.Characteristic of (a) Rainfall storm;(b) storm runoff;(c)Runoff coefficient in over storm event 14

Figure 4: The relationship between Rainfall and runoff through all storm events 15

Figure 5: Schematic illustration of hydrograph separation analysis 16

Figuge 6: Characteristics of runoff components at study catchment 17

Figure 7: The relationship between quick runoff and rainfall 17

Figure 8: The relationship between delayed runoff and rainfall 18

Figure 9: Total suspend sediment and rainfall 19

Figure 10: The relationship between TSS and (a)runoff; (b) precipitation 20

Figure 11: The DO responses to rainfall 21

Figure 12: pH and rainfall in over time 22

ABSTRACT

To evaluate runoff generation and water quality at a small forested catchment, we conducted and monitoring station, collected da from weather station and examined some water quality index (suspend sediment, DO, pH, Chloride, Nitrite, Sulfate) in Luot mountain at VFU in Xuan Mai town, Hanoi capital, Vietnam This study began form 17thJuly to 23th September Based on hydrographic analysis for nine storm events, we found that mean storm precipitation was 139 mm per storm Mean storm flow was 114 mm, corresponding to 82.3% of the runoff coefficient Total rainfall in over study time is 1248

mm where total runoff is 906mm The runoff coefficient is 72.6% The highest precipitation is 399mm (2sd to 5th September) when amount of runoff is 326mm The runoff coefficient is 81.7%; the lowest precipitation is 17mm while amount of runoff is 12mm This coefficient reaches 70.2% This study is a good way to assess the relationship between plantation and hydrological process, assessing the impact of plantation to water quantity and quality Findings of this study will provide an important scientific basis to enhance the protective function of forests planted for Vietnam

I INTRODUCTION

Water is one of the most important factors of natural resources which is necessary for human, ecosystem, and the economic development in mountain and non-mountain areas (FAO, 2005) However, the quantity and quality of fresh water not only in many regions of Vietnam but also in the world (Marzocchi et al , 2009) are increasingly endangered by overuse, misuse, pollution, and especially changing land cover caused by shifting cultivation It is increasingly recognized that both are strongly influenced by forests to water resource because forest maintains water quality through the stable soil, reduce erosion, sediment, and the pollutants from hill slope Forests also affect the amount

of available water in keeping a canopy on rainfall, evaporation of moisture from the surface plant, maintain soil moisture, collect water from fog and maintain of soil infiltration rate They also affect the time of water transport by maintaining or improving the permeability and the ability to accumulate water in the soil (Bosch and Hewlett, 1982) Beside this, climate change is altering forest’s role in regulating water flows and influencing the availability of water resources (Bergkamp, Orlando and Burton, 2003) Moreover, with temperature climate and slope terrain the, threats of water degradation in Viet Nam is very serious Therefore, the relationship between forests and water is a critical issue that must be accorded high priority Management of forest resources has correlation relationship to water resource management and land conservation through changing the amount, timing runoff and soil erosion (FAO, 2005)

Beside this the problems of controlling water quality and quantity, along with managing freshwater fisheries, have also become more complex (Valentinet at., 2008) The effects on the hydrological environment will significantly increase if no efforts are made to minimize the potential impacts Sustainable management of water catchments is one of the options that have to be considered to ensure all development activities have an acceptable impact on both water yield and water quality However, the lack of scientific information on

catchment runoff is hindering the development of solutions and policies in environmental protection and the mitigation of natural hazards in Vietnam Therefore, to tackle these environmental issues, field-oriented observation is necessary In this context, we can assess and develop the management of water quality in forest catchment in Viet Nam

The plantation area in Luot mountain of Vietnam Forestry University have been planted since 1984 when the school was arrived to Xuan Mai Forest ecosystems are planted at Luot mountain is a vital part of training to perform the tasks of the school In addition, since most appear plantation views have said that they are daily flow regulation and improve water quality for the region To understand the opinion of flow regime and water quality from plantation, we installed a monitoring station to measure runoff and precipitation in a 1.6ha mountainous forested catchment at Luot Mountain owned by

Vietnam Forestry University, Hanoi and conducted the study entitled “Evaluating runoff

generation and water quality at a small forested catchment” This study is a good way to

assess the relationship between plantation and hydrological process, assessing the impact

of plantation to water quantity and quality Findings of this study will provide an important scientific basis to enhance the protective function of forests planted for Vietnam

II OVERVIEW OF THE PREVIOUS RESEARCH ISSUES

2.1 Overview

Overland flow and water quality have been researched for many years in hydrology which was born in many years ago They are applied in producing and reached certain achievements The traditional hydrology developed Horton runoff theories in 1930s and 1940s

to research surface runoff formation mechanism For 30 years of research ( Forster G R,1982) [31] Hibbert A R, (1967) [32], by the empirical observations which showed that rainfall intensity is usually smaller than the potential speed of water absorption in Forestry The Hydrology researches in slope terrain developed very fast and instead of ZHANG, 1989 [7] runoff super absorbent theory to form the runoff generation mechanism theories

In recent years, there have been many overland flow research such as Moltranov.A.A.(1960, 1973), Matveev P.N (1973) Santra Reginal (1989), Giacomin (1662)(cited by Anh.K.P [11]… One of the most comprehensive researches which conducted in Russia, is Moltranov researcher He confirmed that, forest soil is possible to transfer water from surface water to groundwater where the area has 25o-30o of slope The drier soil effect of forest in Russia realizes not only in swamps but also in Middle Asia which has low rainfall In Africa, the first overland flow research was established by Hallet professor at Preotoria university in 1929 (Hudson,1981) Generally, Forest soil has high infiltration capacity and low overland flow appearance ( Douglass, 1977; Prichett, 1979) ( cited by Dien[5]) However, when forest are cut down to lead high slope and bare soil can make increase amount of water for overland flow (Ruxton BP, 1967 ; Imenson AC and VIS, 1982) ( cited by Dien [5])

One of the characteristics that related with runoff is permeable Darcy law’s is the typical research about infiltration Base on this, precipitation falls down directly to soil is very high This law proves that with higher infiltration the overland flow is lower

Rainfall characteristic still affect to runoff In Australia, when Oloughlin researched Hydrology in eucalyptus forest, he concluded that overland flow has linear relationship with precipitation by the formation: y= a+bx; whereas x is precipitation, y is overland flows

The results from previous studies in Vietnam and other countries in southeastern Asia showed a large difference in annual runoff coefficients (calculated by dividing annual runoff by precipitation) among countries and different regions within countries The biggest mean annual runoff coefficient was found in Vietnam (27.4%), while the smallest was found in Indonesia (2.1%) However, within a country, the annual runoff coefficient was very different across regions The mean annual runoff coefficients in Laos and the Philippines were 13.3 and 7.6%, respectively

Potential reasons in among countries and regions are differences in catchment scale, annual precipitation, and/or land use type These findings suggested that the study site for our field trip studying water resource management in Vietnam had to be established

in Vietnam itself because of the wide variety of runoff coefficients across regions

In Viet Nam, runoff and erosion was researched in 1970s But from 1995 to now, this problem has concerned more and more The relationship between runoff and erosion has talked by Quynh and Dien(1991) One of the most important results is the overland flow quantitative formula for tropical forest like Viet Nam

2.2 Limitation of the previous studies

Although there are many researches which study in runoff and erosion, are conducted by many professors in the world, but they still have some limitation such as:(1) Runoff generation and formation was studied a long time ago but the systematic hasn’t enough;(2) Most of studies just stop in description level and low quantitative and lack of Mathematic models to ensure confidence to descript runoff generation process On the other hand, Vietnam still uses old methods and equipment than other countries to measure runoff generation and lack of data water quality in forest catchment

III OBJECTIVE, SCOPE OF THE STUDY

3.1 Objective

The main objectives of this study include: (1) Evaluating runoff generation a small forested catchment and (2) examing water quality characteristics of forested catchment

3.2 Scope

The scope of research is about (1) The study site belongs to the forested catchment

at Luot Mountain owned by Vietnam Forestry University, Hanoi;(2)Runoff generation characteristics and water quality observed in natural raining

Figure 1.Location of study site and rainfall, runoff monitoring

Weather station

Gauging station

IV STUDY SITE AND METHOD

4.1 Study site

Study site belongs to in a small catchment at Luot mountain which is owned and managed by Forestry Viet Nam University in Xuan Mai town-Chuong Mi commune –Ha Noi It’s far 35km from Ha Noi in the North-West and 45km from Hoa Binh city in the South – East This belongs to: 20o58’in the North and 105o05’ in the East It ‘s near the High Way 21st in the West, Xuan Mai town in the South and Hoa Son District Luong Son commune Hoa Binh province in the North and South

Luot is the low and medium mountain, this topology is simple It is formed by 2 closed hills The average slope is from 150 to 250 The highest peak hill is 133m, the other is 76m The catchment is covered mainly by acacia, pine, eucalyptus, and some native tree plantation

Study site has 2 main seasons Rainy season begin from April to October and dry season starts from November to March in the next year The detail is as table below

Table 1: Climate- Hydrology indicator at Xuan Mai (Ba Vi weather station)

Temperature regime: Mean temperature per year is 23.10 C, the highest temperature

is 28.50C(June), the lowest temperature is 15.70C (January) Precipitation regime: Mean annual precipitation is 2125 mm Highest mean precipitation is 360mm (August); Lowest mean precipitation is 12mm (December).There are 210 rainy days per year Moisture regime: The study site has high moisture which the distribution doesn’t same between months in year The annual mean moisture is 84.8 %, The highest is 97.9% in April, the lowest is 81.1% in December

4.2 Method

4.2.1 Rainfall monitoring

The rainfall data was collected from 15th July to 23 September by US rain gauges for storm event and by tipping bucket rain gauge of VFU weather station for hourly data

4.2.2 Catchment runoff monitoring

Instruments for the monitoring station is a Parshall flume The flumes were fixed on the exposed channel bedrock and sealed to avoid leakage of stream water Thus, we assumed that all of the storm flow and baseflow was captured at the flumes Water level was monitored

in the flumes and discharge was calculated using the formula for the specificsize of Parshall flume based on water depth (Herschy, 1985) After that I used Omnilog 7 software to download this Parshall Flume data and Microsoft Excel to process data

4.2.3 Observating water quality of catchment runoff

We collected some index of physical, chemical parameters: temperature,, conductivity, sulfate, sediment, DO, Chloride and NO2 that can show water quality characteristics All of materials used as table below:

Table 2: Physical and chemical materials

DO

Glass-stoppered, Dissolved Oxygen 1 Reagent Powder Pillows Dissolved Oxygen 2 Reagent Powder Pillows Dissolved Oxygen 3 Reagent Powder Pillows Measuring Tube, plastic

Sodium Thiosulfate Standard Solution, 0.0109N Starch Indicator Solution,

Sulfate

Sulfaver4 Powder Pillows Dipstick, Sulfate, Measure ClipperCylinder,

graduated, polymethylpentence

Chloride test measuring

Chloride 2 IndicatorPowder Pillow

Silver Nitrate solution

Nitrite test measuring

Color Comparator Box Color Viewing tubes, plastic NitriVer powder pillows for 5-mL sample

a pH

I used pH indicator paper to measure pH after waiting 15s when I put this to water sample to read result

b Suspend sediment(SS):

I calculated SS by 4 steps as below:

1 Collect 25mm of water in VFU Forest small ponds below flume

2 Use filter to keep sediment

3 Make some samples (sediment, sediment+filter,tin)

4 Measure weight of sediment

c DO in the field

To calculate DO, it includes 12 important and carefully steps There are:

1 Submerge the glass – stoppered DO bottle in the water to be tested Allow it to fill to the top Note: collect and prepare the sample in the DO bottle Transferring the sample from one container to another could contaminate it with atmosphere oxygen

2 Be certain that no air bubbles are present by inclining the bottle slightly and inserting the stopper with a quick thrust This will force air bubbles out of the sample If bubbles become trapped in steps 2 or 3, the sample should be discarded and the test begun again Note: start the test immediately after collecting the sample

3 Carefully remove the stopper from the bottle Add the contents of one Dissolved Oxygen 1, and one Dissolved Oxygen 2 Reagent Powder Pillow stopper the bottle firmly

to avoid trapping air

4 Grip the bottle and shake vigorously A delay in mixing the solution may result

in the powder not dissolving properly A flocculent precipitate will form If oxygen is present, the precipitate will be brownish – orange A small amount of powdered reagent may remain at the bottom of the bottle This will not effective the results

5 Allow the sample to stand until the floe has settled half-way and the upper half

on the bottle is clear

6 Shake the bottle again

7 Allow the floe to settle again

8 Remove the stopper add the contents of one Dissolved Oxygen 3 Reagent Powder Pillows