Application of water quality index wqi in assessing surface water quality in bac kan province vietnam

DOCUMENTATION PAGE WITH ABSTRACT Degree program Bachelor of Environmental Science and Management Student ID DTN1453120001 Thesis title Application of water quality index WQI in assessing

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURAL AND FORESTRY

Study Mode : Full-time

Major : Environmental Science and Management

Faculty : Advanced Education Program

Batch : 2014 - 2018

Thai Nguyen, 25/9/2018

DOCUMENTATION PAGE WITH ABSTRACT

Degree program Bachelor of Environmental Science and Management

Student ID DTN1453120001

Thesis title Application of water quality index (WQI) in assessing surface

water quality in Bac Kan province, Vietnam

Keywords Water pollution, Water Quality Index (WQI)

Number of pages 47

Date of submission 25/9/2018

ACKNOWLEDGEMENT

Foremost, I would like to express my sincere gratitude to my advisors Msc Nguyen Van Hieu for their infinite guidance, patience, generous encouragement and supports to me to finish my work step by step I appreciated all the apportunities my advisor offered me by giving me intellectual freedom in my work, engaging me in new ideas, and demanding a high quality of work in all my endeavors

Besides my advisors, I would like to thank to Center for Space and Remote Sensing Research (CSRSR) and Geo-Informatics Research Center (GIRC) of Thai Nguyen University of Agriculture and Forestry (TUAF) for providing me all the necessary facilities and scientific knowledge to complete this thesis and my deep gratitude also goes to Thai Nguyen University of Agriculture and Forestry which helps

me gain to deep knowledge about Environmental science and Management

I would be remiss if I did not thank to fellow labmates in CSRSR and GIRC for their kindness and help in training me and for many valuable advices that given to me whenever I get stuck with my research

Last but not the least, I would like to thank my family for their unconditional love and support they gave me throughtout the research process

Thai Nguyen, 25/09/2018

Student

Dang Chau Giang

TABLE OF CONTENTS

LIST OF FIGURES iv

LIST OF TABLE v

LIST OF ABBREVIATION vi

PART I INTRODUCTION 1

1.1 Research rationale 1

1.2 Research objectives 2

1.3 Significance of study 3

1.4 Limitation of study 3

PART II LITERATURE REVIEW 4

2.1 Study area and water quality in the study area 4

2.1.1 Study area 4

2.1.2 Water quality in the study area 5

2.2 Overview of WQI 6

2.3 WQI construction method 6

2.3.1 Method to build WQI of some countries in the world 6

2.3.2 Method to build WQI in Vietnam 7

PART III METHODS 10

3.1 Stages of research 10

3.2 Statistical methods and aggregation of secondary data 10

3.3 WQI calculation method 18

PART IV RESULTS AND DISCUSSION 22

4.1 Ban Kan hydrographic features 22

4.2 Evaluation of surface water quality in Bac Kan province 22

PART V CONCLUSION 32

5.1 Conclusion 44

5.2 Recommendation 45

LIST OF FIGURES

Figure 1 Map of Study area (Source: Google Earth pro) 5

Figure 2 Chart of BOD5 concentration in surface water stage 1 in 2017 25

Figure 3 Chart of COD levels in surface water stage 1 in 2017 26

Figure 4 Chart of TSS concentration in surface water stage 1 in 2017 26

Figure 5 Chart of BOD5 concentration in surface water phase 1 compared with phase 2 in 2017 36

Figure 6 Chart of COD concentration in surface water phase 1 compared to phase 2 in 2017 36 Figure 7 Chart of TSS levels in surface water phase 1 compared to phase 2 in 2017 37

LIST OF TABLES

Table 1 List of monitoring stations 11

Table 2 Table regulated for qi, BPi values 19

Table 3 Regulated BPi, qi values for DO% saturation 20

Table 4 Table regulated BPi and qi values for pHtime 20

Table 5 Water Quality Index (WQI) at Surface Water Surface Monitoring in Bac Kan province, phase 1 in 2017 27

Table 6 Water Quality Index (WQI) at surface water surface monitoring in Bac Kan province, phase 2 in 2017 38

WQI: Water Quality Index

PART I INTRODUCTION

1.1 Research rationale

Currently, along with the development of the country towards Industrialization - Modernization takes place strongly, the environment in general and the water environment in particular is greatly affected Spontaneous, unplanned activities such as uncontrolled logging, inadequate agricultural practices, and direct discharge into water bodies have resulted in polluted water, clean water shortages is becoming more serious than ever before in less rainy areas

The water is used in the dry season with big quantity, especially the amount of water used for agriculture The total volume of water needed during the dry season in

2000 was 70.7 km3, accounting for 42.4% of total water that can be supply for the dry season (including river water, spring water, groundwater and water from the reservoirs) Moreover, in many areas and river basins, the amount of water needed can be several times the amount of water that can be supplied Vietnam is a developing country Although, receiving much attention from the government, still only 46-50% of urban population and 36-43% of rural population have access to clean water Many people in different regions also have to use water sources that do not meet hygiene standards, resulting in a high proportion of the population is infected: 90% of rural women suffer from gynecological diseases, 95% of children infected with germs, worms etc Water pollution is the cause of the potential risk of diseases in the locality (VNCOLD 2014) Bac Kan is a mountainous province in the Northern part of Vietnam with mountain ranges in the Gam River arch and Ngan Son arc, so it is also home for dense network of

3,513 million m3, including 7 rivers: Cau river, Yen river, Phat Dat river, Bac Giang River, Na Ri River, Hien River and Bang Khau River Bac Kan has more than 40 lead, zinc, gold and stone mining sites Due to poor management, most mines have no wastewater treatment system, so waste water in and after extraction are discharged directly into rivers and streams, causing the water in the mining areas seriously polluted (

In order to overcome the above difficulties, one or more indicator systems should

be used to allow an integrated view of water quality in terms of physical and chemical indicators of water resources, evaluated on a uniform scale, understandable with common objects One of the indicator systems is the "Water Quality Index (WQI), which has the advantage of being simple, easy to understand, generalizable and can be used for the purpose of assessing the quality of water in space and time Beside of that, WQI is a good source of information for the community, for non-water professionals who were not in the field of water environment For the reasons mentioned above, I selected the topic

"Application of WQI in assessing surface water quality in Bac Kan province, Vietnam”

1.2 Research objectives

- Learn about the WQI and hydrographic features in Bac Kan province

- Collection of documentary information: inherit the results available, collected,

analyzed through reports, research topics, and reports on environmental impact assessment

- Processing of raw data and through the WQI calculation and assessment of water

quality for each river and stream in the Bac Kan city

1.3 Significance of study

Study based on WQI parameters and WQI calculations on all observations in the province to assess the surface water quality in large rivers and lakes and to propose appropriate management measures

1.4 Limitation of study

In this study, new monitoring and WQI values were obtained for the second round

of 2017, which only compared the changes in environmental quality during the year, which could be compared with previous years to assess the changing water environment

between years

PART II LITERATURE REVIEW

2.1 Study area and water quality in the study area

The province is in the northeast midland mountainous area of Vietnam Its terrain has the highest altitude among the 11 provinces of the region Forest area dominates more than 95% of the province The remainder is available for agricultural and other uses Due to this rugged and forested topography, development of water resources has been limited resulting in exploitation of its forest resources; this has caused degradation

of the forests The topography is highly variable, varying from 1,640 meters (5,380 ft.) (Highest point in the Khie Thiouing mountains in the province) to the lowest point of 40 meters (130 ft.) in the Cho Moi District There are numerous rivers and streams flowing through the province, each with small catchment areas However, most of them have steep slopes and short lengths Out of the total population, 83% are dependent on agriculture (https://en.wikipedia.Bac kan Province)

This thesis just focuss on analaysis the main river and lake in Bac Kan province: Cau river , Nang river , Ba Be Lake , Bac Giang river

Figure 1 Map of Study area (Source: Google Earth pro)

2.1.2 Water quality in the study area

In the rivers in Bac Kan, Cau River is most polluted by the production, business, mining and human activities In addition, Ba Be Lake has been subjected to local pollution caused by waste oil from dozens of Ba Be Lake tourist motorboats and beer cans and soft drinks of travelers throwing away On the shores of the lake side of the motor boat appeared many oil spills

The phenomenon of surface water pollution only occurs locally, in general, the quality of surface water here is relatively good Distribution of main surface water pollution points in Cho Don district; Some locations of Bach Thong district are discharged by the wastewater from Cam Giang Cement Plant and wastewater discharged from Cau Giay Town to Cau River Basin; Some points in Bac Kan town due to domestic wastewater of households in town, production facilities, typically the paper factory to

2.2 Overview of WQI

WQI is a composite index calculated from the determined water quality parameters through a mathematical formula WQI is a quantitative description of water quality and is represented by a scale The use of domestic organisms as an indicator of German cleanliness since 1850 is considered the first study of WQI, and now many countries have developed and applied the WQI, calculated from different parameters

we obtain a single index Water quality can then be compared against that indicator, which is a simple method of analyzing a range of biochemical parameters for evaluating water quality

The main applications of WQI include: To serve the decision-making process (financial allocation and identification of priority issues); water quality zoning; standard execution (response or not); analysis of water quality in space and time; release information to the community; scientific research (in-depth, macro-study on impact assessment of urbanization to regional water quality, assessment of emission control efficiency [Nguyen Xuan Hoan, 2017]

2.3 WQI construction method

2.3.1 Method to build WQI of some countries in the world

There are many countries that have adopted WQI in practice, as well as many scientists studying WQI models The Horton (1965) is the first WQI built on a scale

In the United States, WQI is built for each state, with most states approaching the method of the National Sanitation Foundation (NSF, 2004) In Canada, the method developed by the Canadian Environmental Protection Agency (CCME, 2001) In Europe, European countries were mainly developed from the American WQI

However, each country or locality chooses its own subtraction parameters and methods The countries of Malaysia and India are developed from the United States WQI, but each country can build a wide range of WQIs for each use (such as domestic water supply, agriculture, industry .) Multiplication and generalized WQI are calculated as the weighted average of the individual WQIs

The Belgian method uses points 1 to 4 to classify water quality, not to mention the importance of each parameter and the numbers of calculation parameters are limited New Zealand identified water quality for recreational activities exposed to water by the smallest subtraction value According to the Bhargava model (India), the individual WQI is calculated for each water use purpose [The Nguyen, 2016]

2.3.2 Method to build WQI in Vietnam

"Building WQI for assessment of water quality management system of Dong Nai River" by Dr Ton That Lang - College of Natural Resources and Environment in Ho Chi Minh City was published in the 19th edition of the Scientific Seminar of the Institute of Science and Technology of Natural Resources and Environment

In the article "WQI Study to evaluate and delineate the quality of the Bassac River", Dr Ton That Lang constructed the water quality index of the Hau River system according to the Delphi method

The topic of "Study on water quality zoning under WQI and assessing the use

of rivers and canals in HCMC" (Le Trinh, 2008) has applied and improved WQI models of sanitation The United States of America (Bhargara) to partition water quality and assess the water use of rivers

Study on the level of organic pollution in old Hanoi inner lakes through the Kannel Water Quality Index (Do Kieu Tu, 2010), using the WQIkannel index to assess the water quality of 22 lake in the inner city of Hanoi The WQIkannel was refined by the Delphi method to provide a general equation for indexing

WQI kannel:

For n is the sum of the parameters Ci is the value of parameter i after normalization Pi is the corresponding weight for each parameter, the value Pi is about 1-4 The most important value for maintaining aquatic life is a value of 4 (for example, dissolved oxygen) and the value indicated for less influential parameters (e.g., chloride content) K is the subjective constant; K is 0.25 -1 corresponding to the highly polluted water to the less polluted water as originally stated Thus, most of the methods in Vietnam have been applied on the basis of the United States WQI (NSQ-WQI), Bharavara (India) and the Canadian Environment Ministry (WQI -CCME) have adapted accordingly with the right water quality for each region For the purpose of the topic, the method of calculating the water quality index by the Vietnam Environment Administration (VEA), Ministry of Natural Resources and Environment (VEA), 2011) was chosen to best reflect current situation Surface water pollution in the area of Bac Kan province, serving the assessment, zoning and management of surface water quality throughout 2.3 The scientific basis of the construction of criteria for locating environmental pollution around

The essence of pollution zoning / or surrounding environmental quality is the division of a geographical area of a province or city into regions of varying degrees of actual environmental pollution The set of indicators to assess the environmental pollution has been identified (Cude, 2001) In most countries in the world have issued national environmental quality standards, such as the quality of air environment, surface water quality and coastal water quality Environmental quality standards and limits on the concentration of pollutants in the maximum allowable environment, commensurate with the conditions in which humans are exposed to the environment , long term, does not cause harm to health and living conditions, does not cause any symptoms of illness (King, 2007).Contaminated environment is the environment that contains one or more pollutants whose concentration exceeds the maximum allowable limit specified in the environmental standard / regulation (Grosvenor K, 2007).High or low pollution levels shall be determined according to the ratio between the actual pollutant concentration and the permitted concentration value The criteria for locating the polluted areas are the specific criteria (quantitative) for Assessment of different levels of environmental pollution, different polluted areas, divided by boundary lines with different levels of environmental pollution The "Environmental Quality Index (EQI)," as used for the environment, is often used to assess the degree of environmental pollution or environmental quality classification For the surface water quality is WQI (Water Quality Index), for sea water quality is SWQI (Sea water Quality Index), for soil environment is SoQI (Soil Quality Index (US EPA, 1999)

PART III METHODS

The process of calculating and using WQI in water quality assessment includes the following steps:

Step 1: Collecting and collecting data from the surface water surface monitoring station in 2 observations in Bac Kan city

Step 2: Calculate the WQI values of the parameters according to the formula;

Step 3: Calculate WQI;

Step 4: Compare the WQI with the water quality assessment tables

3.2 Statistical methods and aggregation of secondary data

Monitoring data for DO parameters, temperature, BOD5, COD, N-NH4 +, PO43-, TSS, turbidity, total coliform, pH were collected from the periodic monitoring report.in April and June, 2017 from the Department of Natural Resources and Environment of Bac Kan province to calculate the WQI values for each monitoring position of the two observations and comparisons

P-Table 1 List of monitoring stations (Report on environmental monitoring results of Bac Kan province-2017)

No Name of the

monitoring point

Sample symbol Monitoring Type

Sampling locations

Description of the monitoring point

X (m) Y (m) Longitude Latitude

2.450.870 430.019 - Location: Cau River water at Duong Quang Bridge

- Purpose, meaning: Current status and the impact of the development of Cau River area to water quality from the upstream to Bac Kan city

105o49’290 22o09’296

2 Nam Co stream

Background monitoring

through Quang Son

residential area, Doi

105o49’959 22o09’247

4 Pa Danh stream NMTX-6 Environmental

impact monitoring

2.451.023 432.610

- Location: Pa Danh stream

- Purpose, meaning: Assess the level of pollution in Pa Danh stream

105o50’797

22o09’260

Kien and Duc Xuan

wards

105 o 49 ’ 969 22 o 09 ’ 144 - Purpose, meaning: Assess the level of pollution in the

stream running through Phung Chi Kien ward and Duc Xuan ward

6 Khuoi Cuong spring

Environmental impact monitoring

2.442.552 436.007 - Location: Khuoi Cuong spring water

- Purpose, meaning: To assess the level of pollution in Cuoi Cuong spring water flowing through Xuoc Hoa commune

105o52’794 22o04’804

7

Water of Nang river

at Tin Don Bridge

(Cho Ra town)

NMBB-1 Background

monitoring

2.484.080 419.883 - Location: Water of Nang river at Tin Don Bridge

- Purpose, meaning: Current status and evolution of Nang River water quality from the upstream to Cho Ra town

105o43’294 22o27’264

8 Water of Nang River

at Buoc Lom (wharf) NMBB-2

Background monitoring

2.484.180 414.816 - Location: Nang River water at Buoc Luom

- Purpose, meaning: The status and development of the quality of Nang River from Cho Ra town to Khang Ninh commune

105o40’340 22o27’305

9 Water of Ba Be lake

(Lake 1) NMBB-3

Background monitoring

2.478.907 409.169 - Location: Ba Be Lake Water (Lake 1)

- Purpose, meaning: Status and development of water quality in Lake 1

105 o 37 ’ 077 22 o 24 ’ 428

10 Water of Ba Be lake

(Lake 3) NMBB-4

Background monitoring

2.482.717 408.491 - Location: Ba Be Lake water (lake 3)

- Purpose, meaning: The current state and evolution of water quality in Lake 3 near the position with the Nang River

105o36’668 22o26’494

11

Cho Lon spring

water (Pac Ngoi

2.456.688 435.846 - Location: Na Co stream at Cam Giang bridge

- Purpose, meaning: Assessment of Na Cam stream quality from Phu Thong town to Cam Giang commune (Na Cu bridge) The impact of the operation of Cam Giang Gang

105o52’666 22o12’463

15 Phu Thong stream

(at Suoi To bridge) NMBT-2

Background monitoring

2.462.019 435.603 - Location: Phu Thong stream water at To stream bridge

- Purpose, meaning: Current status and development of Phu Thong stream water quality after flowing through the town area

2.450.986 436.639 - Location: Na Cu stream in Nguyen Phuc commune

- Purpose, meaning: Current situation and quality of Na

Cu stream before confluence with Cau river

105o53’140 22o09’375

17 Sy Binh stream in

My Thanh commune NMBT-4

Environmental impact monitoring

2.450.515 439.457 - Location: Sy Binh spring water in My Thanh

commune

- Purpose, meaning: Assessment of Na Cu stream quality from Phu Thong town to Cam Giang commune (Na Cu bridge) The impact of the operation of Cam Giang Gang

105o54’781 22o09’126

18 Na Tum stream,

Ngoc Phai commune NMCĐ-1

Background monitoring

2.452.953 404.575

- Location: Na Tum stream, Ngoc Phai commune- Purpose, meaning: Current status and quality of Na Trom stream, Ngoc Phai commune

105o34’484 22o10’353

commune) 105 o 33 ’ 524 22 o 01 ’ 182 - Purpose, meaning: Current status and evolution of

water quality in the river

20

Quang Bach - Nam

Cuong Stream (Nam

Cuong commune)

NMCĐ-3 Background

monitoring

2.475.182 407.507

- Location: Quang Bich - Nam Cuong waterfall

- Purpose, meaning: Current status and quality of Quang Bach - Nam Cuing spring water

105o36’111 22o22’407

21

Ban Thi Stream

(near the 50-bed

hospital)

NMCĐ-4 Environmental

impact monitoring

2.458.617 395.840

- Location: Ban Thi stream near the hospital 50 beds

- Purpose and meaning: Assess the level of pollution of the This Stream stream due to the activities of Cho Dien mining and the activities of the people in Ban Thi commune

105o29’379 22o13’392

22

Water of Pho Day

River in Bang Lang

- Location: Cau River water in Dong Vien commune

- Purpose, meaning: Status and development of Cau River water quality Impacts by nature, agro-forestry activities, etc

105o39’675

22 o 08 ’ 536

2.437.028 405.495

River of Yen Nhuan

commune (second

branch)

monitoring 105 o 35 ’ 073 22 o 01 ’ 728 commune (second branch)

- Purpose, meaning: Status and development of infection in the water of Pho Day River (second branch) due to activities of people's livelihood, agriculture and forestry

- Location: Cau River water in Nong Ha

- Purpose and significance: To assess the level of water pollution in the Cau river after the waste water

discharge position of the B & H paper factory

2.426.197 427.284 - Location: Cau River water in Thanh Binh

- Purpose, meaning: Status and development of water quality of Cau River from Nong Ha to Thanh Binh

105 o 47 ’ 765 21 o 55 ’ 721

27 Cau river water (at

Yen Dinh bridge) NMCM-3

Background monitoring

2.422.391 426.984 - Location: Cau River water at the

Yen Dinh Bridge

- Purpose, meaning: Current status and development of Cau River water quality from Thanh Binh to Yen Dinh bridge

105o47’601 21o53’858

28 Cho Chu Spring

Water (O Ga Bridge) NMCM-4

Background monitoring

2.420.392 425.669 - Location: Cau River water at Tham temple

- Purpose, meaning: Current status and development of water quality of Song Cau river from Yen Dinh bridge

to Tham

105o46’845 21o52’772

- Purpose, meaning: Status and progress of water quality

in Bac Giang river from upstream to Luong Thuong commune

106o07’832 22o12’904

33

Bac Giang river

water (Pac Cap I

dam)

NMNR-3 Background

monitoring

2.457.416 461.910

- Location: Bac Giang river water (Pac Cap I dam)

- Purpose, meaning: Current status and development of water quality in Bac Giang river before confluence with

2.457.301 461.836 - Location: Na Ri River (Pac Cap II dam)

- Purpose, meaning: Current status and evolution of water quality Na Ri River from Hao Nghia Bridge to Pac Cap II Dam

106o07’789 22o12’840

35

Bac Giang river

water (Hat Deng

bridge)

NMNR-5 Background

monitoring

2.460.226 467.468 - Location: Bac Giang river water (Hat Deng bridge)

- Purpose, meaning: Status and development of water quality in Bac Giang River from Pac Tra to Hat Deng Bridge

2.445.493 458.962 - Location: Na Ri River (Hao Nghia Bridge)

- Purpose, meaning: Current situation and quality of Na

Ri river water from upstream to Hao Nghia bridge

106o06’735 22o06’439

37

Van Tung stream

water (Van Tung NMNS-1 Background

monitoring

2.481.422 447.983 - Location: Van Tung stream water

- Purpose, meaning: Current situation and quality of stream water in Van Tung Commune, a tributary of Bac

105 o 59 ’ 680 22

o 25’890

38 Na Phac stream (at

Na Phac bridge) NMNS-2

Background monitoring

2.475.650 437.268

- Location: Na Phac stream (at Na Phac bridge)

- Purpose, meaning: Current status and quality of Na Phac stream water

40 Thuan Mang Stream

(Ban Giang Bridge) NMNS-4

Background monitoring

2.471.578 449.858 - Location: Thuan Mang Stream (Ban Giang Bridge)

- Purpose, meaning: Status and development of Thuan Mang spring water quality

3.3 WQI calculation method

WQI is calculated according to the formula in the technical manual for calculation

of water quality index according to Decision No 879 / QD-TCMT dated 01 July 2011 of the Director General of Vietnam Environment Administration

* Calculate WQI parameters (WQI SI )

- Calculated WQISIfor some parameters: BOD5, COD, N-NH4+, P-PO43-, TSS,

Turbidity, Total coliform By Equation 1:

Table 2 Table regulated for qi, BPi values

- Calculate the WQI value for DO (WQIDO): Calculated through the DO value

of the saturation percentage DO saturation value:

DO value of the saturation percentage:

DO%saturation= DODissolved / DO*100

Dissolved DO: DO value was monitored (Calculated by mg/l)

Calculate WQIDO by equation 2

In which:

Cp : DO% saturation value

BPi, BPi+1, qi, qi+1: are values corresponding to i, i + 1 in Table 3

N-NH4 (mg/l)

P-PO4 (mg/l)

Turbidity (NTU)

TSS (mg/l)

Coliform (MPN/100

Table 3 Regulated BPi, qi values for DO% saturation

If DO% saturationvalue ≤ 20 then WQIDO equals to 1

If 20 < DO% saturation value <88, then WQIDO is calculated according to equation

2 and uses above Table

If 88 ≤ DO% saturation ≤ 112 then WQIDO equals to 100

If 112 < DO% saturation< 200 then WQIDO is calculated according to equation 1 and uses above Table

If DO% saturation ≥ 200 then WQIDO equals to 1

Table 4 Table regulated BPi and qi values for pHtime

If the pH value ≤ 5.5 then WQIpH is equal 1

If 5.5 < pH value < 6 then WQIpH is calculated according to equation 2 and is used by above table

If 6 ≤ pH value ≤ 8.5 then WQIpH is equal to 100

If 8.5 ≤ pH value ≤ 9 then WQIpH is calculated according to equation 1 and is used by above table

If the pH value is 9 then WQIpH is equal 1

*Calculate WQI

After calculating the WQI for each of these parameters, the calculation of WQI

is based on the following formula

In which:

WQIa: Calculated WQI for 05 parameters: DO, BOD 5 , COD, N-NH 4 , P-PO4

WQIb: Calculated WQI for two parameters: TSS, turbidity

WQIc: The calculated WQI value for the Total Coliform parameter

WQIpH: The calculated WQI value for the pH parameter

Note: The WQI value after calculation will be rounded to integer

- Compare on a scale

Use the following table to determine the WQI value corresponding to the water

quality for comparison and evaluation, concretely as follows:

91 - 100 Blue It is well used for water supply purposes

76 - 90 green It is used for water supply purposes but requires

appropriate treatment measures

51 - 75 yellow Used for irrigation and other similar purposes

26 - 50 Orange Used for navigation and other similar purposes

0 - 25 red Heavy polluted water, need treatment measures in the future