Study on the pollution of song cai river under the impact of climate change and suggestion of remedies for recovering the water quality

MINISTRY OF EDUCATION AND TRAINING
NHA TRANG UNIVERSITY
------------------o0o------------------

TA LE DANG KHOI

STUDY ON THE POLLUTION OF SONG CAI RIVER
UNDER THE IMPACT OF CLIMATE CHANGE AND
SUGGESTION OF REMEDIES FOR RECOVERING THE
WATER QUALITY

MASTER THESIS

KHANH HOA - 2017


MINISTRY OF EDUCATION AND TRAINING
NHA TRANG UNIVERSITY
------------------o0o------------------

TA LE DANG KHOI

STUDY ON THE POLLUTION OF SONG CAI RIVER
UNDER THE IMPACT OF CLIMATE CHANGE AND
SUGGESTION OF REMEDIES FOR RECOVERING THE
WATER QUALITY
MASTER THESIS
Marine Ecosystem based Management
and Climate Change

Major:

Code:
Topic allocation Decision

772/QĐ-ĐHNT dated 20/9/2016

Decision on establishing the
Committee:

461/QĐ-ĐHNT dated 16/5/2017

Defense date:

3/6/2017

Suppervisors:
Assoc. Prof. NGO DANG NGHIA
Prof. SIGURD STEFANSSON
Prof. HENRIK GLENNER

Chairman:
Assoc. Prof. PHAM QUOC HUNG

Faculty of Graduate Studies:

KHANH HOA - 2017


UNDERTAKING
I undertake that the thesis entitled: “ Study on the pollution of Song Cai River
under the impact of climate change and suggestion of remedies for recovering the

water quality “ is my own work. The work has not been presented elsewhere for
assessment until the time this thesis is submitted.
Khanh Hoa, Day........ month.......year 2017
Author

Ta Le Dang Khoi

iii


ACKNOWLEDGMENT

I would like to express the deepest appreciation to The Institute for
Biotechnology and Environment of Nha Trang University for helping and giving best
conditions me finish my thesis.
My special thanks go to Assoc. Prof. Ngo Dang Nghia for the continuous
support of my Ph.D study and research, for his patience, motivation, enthusiasm, and
immense knowledge. His guidance helped me in all the time of research and writing of
this thesis.
Last but not least, I would like to thank my family: my parents and to my
brothers and sister for supporting me spiritually throughout writing this thesis.
Thank you!
Khanh Hoa, Date .... month .... year 2017
Author

Ta Le Dang Khoi

iv

TABLE OF CONTENTS
Chapter 1. GENERAL ..................................................................................................1
1.1. Introduction ..............................................................................................................1
1.2. Imperiousness ...........................................................................................................7
1.3. Natural characteristics ..............................................................................................8
1.3.1. Geographical location............................................................................................8
1.3.2. Climate Features ....................................................................................................9
1.3.3. Features of major rivers and streams in Khanh Hoa Province ............................13
1.3.4. Current situation of water resources exploitation................................................13
1.4. Economic and social characteristics.......................................................................14
1.4.1. Population and population distribution ...............................................................14
1.4.2. Economic growth.................................................................................................14
1.5. Scientific and practical meaning ............................................................................15
1.5.1. Scientific meaning ...............................................................................................15
1.5.2. Practical meaning ................................................................................................15
Chapter 2. SUBJECT AND RESEARCH METHODS ...........................................16
2.1. Object of research...................................................................................................16
2.2. Subject and scope of research.................................................................................16
2.2.1. Subject of research ..............................................................................................16
2.2.2. Scope of research.................................................................................................16
2.3. Research content.....................................................................................................17
2.4. Research methods ...................................................................................................17
2.4.1. Surey, sampling and analysis methods................................................................17
2.4.2. Method of building water quality indicators .......................................................18
2.4.3. Method of mathematical models (MIKE 11 model) ...........................................24
2.4.4. Calculation grid establishment in MIKE 11........................................................27
2.4.5. Climate change scenarios ....................................................................................30

v

Chapter 3. RESULTS AND DISCUSSION ..............................................................33
3.1. The current status of waste discharge sources........................................................33
3.1.1. Sources of waste affecting the water quality of the Cai river .............................33
3.1.2. Direct waste sources ............................................................................................33
3.1.3. Discharge sources through tributary river and canal systems .............................36
3.2. Assessment of surface water quality in the study area ...........................................38
3.3. Evaluation of the trend in surface water quality with water quality index (WQI).41
3.4. Sources of water pollution in the future .................................................................44
3.4.1. Sources of industrial waste water ........................................................................44
3.4.2. Forecast of wastewater from urban and residential areas....................................46
3.5. Forecasting the influence of waste water on the water quality of Cai river (Mike
11) ..................................................................................................................................48
3.6. The simulation of water quality with the impact of climate change, according to
different emission scenarios ..........................................................................................48
3.6.1. Climate change scenarios ....................................................................................48
3.6.2. The result of Scenario simulation under the impact of climate change in 2020 .49
3.6.3. The result of Scenarios simulation under the impact of climate change in 203057
LIST OF REFERENCES............................................................................................68
APPENDICES

vi


ABBREVIATIONS
CCME: Canadian Council of Ministers of the Environment
DO:

Dissolved Oxygen

EQI :

Environment Quality Index

GIS:

Geographic Information System

IC:

Industrial Cluster

IP:

Industrial Park

OWQI: Oregon Water Quality Index
QCVN 40:2011/BTNMT: National technical regulations on industrial waste
water quality
QCVN 14:2008/BTNMT: National technical regulations on household waste
water quality
QCVN 08-MT:2015/BTNMT: National technical regulations on surface water
SS:

Total Suspended Solid

TC:

Total Coliform

WQI:

Water Quality Index

vii


LIST OF TABLES
Table 1.1. Average temperatures in the years 2012, 2013, 2014, 2015 ..........................9
Table 1.2. Monthly rainfall (mm)..................................................................................11
Table 1.3. Morphology of rivers and streams in Khanh Hoa ........................................13
Table 1.4. Population in the research area in 2014 .......................................................14
Table 2.1. Locations of sampling the surface water in the Cai River ...........................17
Table 2.2. Results of classification of water quality according to BC Index ................19
Table 2.3. Specified values qi, BPi................................................................................21
Table 2.4. BPi and qi values corresponding to DO% saturated ...................................22
Table 2.5. Specified BPi and qi values with pH parameter...........................................22
Table 2.6. Water quality assessment .............................................................................23
Table 3.4. Positions of the tributary rivers and canals flowing into the Cai River in the
study area .......................................................................................................................37
Table 3.7. Locations of sampling the surface water in the Cai River ...........................38
Table 3.8. The results of calculating WQI of Cai River in the rainy season.................41
Table 3.9. The results of calculating WQI of Cai River in the dry season ...................42
Table 3.11. Prediction of wastewater flow generated from the IPs and ICs in 2020,
2030 ...............................................................................................................................45
Table 3.18. Prediction of population in reseach area until 2020, 2030.........................46
Table 3.26. The load of domestic wastewater sources under 3 scenarios in 2020........47
Table 3.27. The load of domestic wastewater sources under 3 scenarios in 2030........48
Table 3.28. The amount of change in precipitation (%) compared to the baseline period
from 1980 to 1999 of Khanh Hoa province, according to the average emissions

scenario (B2)..................................................................................................................49
Table 3.29. The amount of change in precipitation (%) in comparison to the baseline
period from 1980 to 1999 of Dak Lak province, according to the average emissions
scenario (B2)..................................................................................................................49
Table 3.30. The amount of change in temperature (oC) in comparison to the baseline
period from 1980 to 1999 of Khanh Hoa province, according to the average emissions
scenario (B2)..................................................................................................................49
viii


LIST OF FIGURES
Figure 1.1: The map of research area ..............................................................................8
Figure 1.2. The distribution of average temperature in Khanh Hoa province ..............10
Figure 1.3. The distribution of rainfall in the dry seaso ................................................12
Figure 1.5. The distribution of total annual rainfall in Khanh Hoa Province ...............12
Figure 2.1: Diagram of research area ............................................................................16
Figure 2.2: Locations of sampling the surface water in the study area .........................18
Figure 2.3: Description of continuity equation .............................................................24
Figure 2.4: Diagram of flow between 2 calculated cross sections ................................25
Figure 2.5: Research area sitemap.................................................................................27
Figure 2.6: Calculation grid in MIKE 11 ......................................................................28
Figure 2.7: Cross section location .................................................................................28
Figure 2.8: Edited cross sections in MIKE 11...............................................................29
Figure 2.9: Sub-basins in the reseach area ....................................................................30
Figure 2.10: Four families of greenhouse gas emission scenarios ................................31
Figure 3.1. Positions of the discharge sources in the study area ...................................35
Figure 3.2. The tributary rivers and canals flowing into the Cai River.........................37
Figure 3.3: Locations of sampling the surface water in the study area .........................40
Figure 3.4. Current status of water quality in Cai River is represented by WQI in the
dry season ......................................................................................................................43

Figure 3.5. Current status of water quality in Cai River is represented by WQI in the
rainy season ...................................................................................................................43
Figure 3.6. DO changes in some locations according to Scenario 1 .............................50
Figure 3.7. BOD changes in some locations according to Scenario 1 ..........................50
Figure 3.8. NH4 changes in some locations according to Scenario 1 ...........................51
Figure 3.9. PO4 changes in some locations according to Scenario 1............................52
Figure 3.10. DO changes in some locations according to Scenario 2 ...........................52
Figure 3.11. BOD changes in some locations according to Scenario 2 ........................53
Figure 3.12. NH4 changes in some locations according to Scenario 2 .........................53
Figure 3.13. PO4 changes in some locations according to Scenario 2..........................54
ix


Figure 3.14. DO changes in some locations according to Scenario 3 ...........................54
Figure 3.15. BOD changes in some locations according to Scenario 3 ........................55
Figure 3.16. NH4 changes in some locations according to Scenario 3 .........................56
Figure 3.17. PO4 changes in some locations according to Scenario 3..........................56
Figure 3.18. DO changes in some locations according to Scenario 1 ...........................57
Figure 3.19. BOD changes in some locations according to Scenario 1 ........................57
Figure 3.20. NH4 changes in some locations according to Scenario 1 .........................58
Figure 3.21. PO4 changes in some locations according to Scenario 1..........................58
Figure 3.22. DO changes in some locations according to Scenario 2 ...........................59
Figure 3.23. BOD changes in some locations according to Scenario 2 ........................59
Figure 3.24. NH4 changes in some locations according to Scenario 2 .........................60
Figure 3.25. PO4 changes in some locations according to Scenario 2..........................60
Figure 3.26. DO changes in some locations according to Scenario 3 ...........................61
Figure 3.27. BOD changes in some locations according to Scenario 3 ........................61
Figure 3.28. NH4 changes in some locations according to Scenario 3 .........................62
Figure 3.29. PO4 changes in some locations according to Scenario 3..........................62

x


ABSTRACT
The Cai river played a huge role in providing fresh water, serving people's
livelihood, economic development - social, however due to the waste water of
production facilities, business and domestic wastewater untreated, wastewater has
been directly into the river and make the river water quality decline, many indicators
such as BOD5, COD, TN, TP higher than standards allow. Currently, due to the pace
of development population, industry, agriculture, tourism and services are increasing,
require the demand to use and discharged large amounts of waste, but has not invested
commensurate in infrastructure so most of the water from these areas are not treated
and discharged directly into canals, polluting the environment increasingly severe,
especially the surface water environment.
To solve these problems exist above, practitioner perform build arguments based
on scientific grounds, realistic assessment of river water, polluting sources, evolutions
and trends in future for the Cai river basin, therefore implementing the thesis “ The
study of determining the scope and level of the Cai river pollution (section crossing
Dien Khanh district and Nha Trang city), analysing the causes and proposing
protecting solutions” is necessary and urgent. The results of the research performed
will generalise the current status of the water environment at the research area, is the
basis of scientific and practical to help management agencies policies planning,
development planning of the social economy pertain to protection and sustainable
development of the environment, especially the Cai river water environment.

xi


Chapter 1. OVERVIEW
1.1. Introduction

General management of river basin is strongly and closely related to water
resources management. In 1977, Mar del Plate Conference started the water decline in
the world and proposed International Water Program in 10- year-period (1980-1990).
Then in Dublin Conference 1992, International Association chose some basic
principles of substantial water use. In recent years, there are many researches and
practices about general management and water resources use based on river basin in
the world and they have high theoretical and practical results.
In other nations in the world, pollutions or qualities of surrounding environment
are zoned in a certain period, about once 5 years or 10 years, for example, in the years
1990, 2000 and 2005. In terms of the status quo of economic and social development
and defined zoned pollution time, the variety of pollution situation of surrounding
environment is mainly based on natural conditions. Environmental rivers pollution is
based

on

their

flow

rates,

speeds,

movement

directions

and

water

temperatures,…Therefore, in many nations in the world, there are 2 main approaching
methods to zone pollutions or qualities of surrounding environment as below:
Calculation method according to the model of diffusing environmental pollution
by using Geographic Information System (GIS): This method requires enough data
about waste sources causing environmental pollution (location, flow rate, kind of
waste, means of release and physical properties of waste sources) and about climate,
river, sea, topographical, hydrogeological conditions of researched area. In this
method, contour lines can be drawn quite exactly, which means that the researched
area can be zoned and divided into different sections with different pollution rates.
Method of summarizing, analysing, counting statistics of observing real
environment: This method requires a system of complete observation stations and
distribution of measured points which cover the whole researched area and the thicker
measured points are distributed, the more exact zoning pollution is. Observation time
must be suitable so that the observation results reflect environmental pollution
situation correctly. The zoning pollution based on analysing and counting data of
environment observation often has approximately right value, but it is basic, practical
1


and often used in many nations in the world. In many cases in which there is a lack of
environment observation data, the calculation method of according to the model of
diffusing environmental pollution is combined to zone pollution or qualities of
surrounding environment.
To evaluate environmental pollution level or classify environmental qualities in
the world, Environment Quality Index – EQI is used. AQI is used for air environment,
WQI is used for water surface environment, SWQI is used for inshore environment.
EQI model was first proposed and applied in America in 1965-1970 and is
currently widespread in many states. Nowadays, this model has deployed applied

researches in many nations such as India, Canada, Chile, England, Taiwan, Australia,
Malaysia,...EQI is considered as an effective method to environment managers in
supervising, checking and managing environment qualities, evaluating how effective
policy-planners are. Before 1990, EQI used to be environmental quality indexes to
each separate parameter (pollutant). After 1990, general environmental quality indexes
have been used synthesizing many special pollutants of each defined environment such
as synthesized EQI to air environment, surface water of basin river environment and
inshore environment. The way of classifying pollution level based on individual
pollutant has many disadvantages:
(1). It is difficult to classify environmental quality for one certain purpose of
using, For example, to surface water environment, according to Vietnamese regulation
named QCVN 08:2008/BTNMT about river water quality column A (type A1- meet
standards of Domestic Water Supply) and column B (type B1- not meet standards of
Domestic Water Supply) to parameters of dissolved oxygen (DO), total suspended
solid (SS) and total coliform (TC) equivalent to DO ≥ 6 mg/L and 4 mg/l; TSS = 20
mg/L and 50 mg/L, TC = 2500MPN/100ml and 7500MPN/100 mL. However, in
reality, one river meets type A1 about TSS and TC, while the other meets type A1
about TSS, but both of them do not meet type A1 about DO and TC or meet type A1
about DO, TSS but not meet type A1 and B1 about TC,… Therefore, this river or the
other meets the water quality to what type of surface water? This cannot be answered
based on analysis of environment quality index to each parameter.
(2). In the other hand, depending on different purposes of using, each parameter
has a different importance. For example: turbidity and total coliform are important to
2


direct access (taking shower, swimming), but they are not important to agricultural
irrigation supply. Temperature, salinity, NH4+ are not important to bathing water but
very important to aquaculture water…Obviously, in these cases, it is quite difficult to
conclude that water quality of a river or a stretch of the river meets type A1, A2, B1 or

B2 and water quality which meets standards of a purpose, but not meet the other
purpose. But this leads to a difficulty in zoning areas, classifying water quality,
deciding in exploitation ability of a river or a stretch of the river for one or some
purposes of using.
(3). When evaluating water quality based on many separate indexes, the
development of general water quality of a river or a stretch of the river cannot be seen.
Hence, it is quite difficult to compare water quality in a period with that in other ones
(according to months or seasons), present water quality with that in the
future...Therefore, it is quite difficult to supervise the development of water quality
and evaluate the effect of investment in protecting water sources and monitoring water
pollution,...
(4). When evaluating water quality

based on many separate indexes, only

scientists or specialist managers in water can understand the results, hence it is quite
difficult to inform the water quality to the public and state management agencies,
leaders to make right decisions on water sources protection and exploitation.
To overcome these difficulties, there needs a index or a system of indexes
allowing to quantify general environmental quality (which means reflecting
environmental quality index according to a unified band score) and be able to describe
the combination of many chemical, physics and biological ingredient concentration
and the importance of each pollutant index to one certain purpose. One of these
indexes is Water Quality Index(WQI). Basically, WQI is means of Maths to calculate
values of experiments to release results of indexes reflecting water quality of a certain
basin such as lake, river, runnel. In other way, WQI is a Maths formula simulating
pollution level of river, lake water sources based on values analysing special
parameters about water quality. According to it, we can know about quality and
pollution level of a stretch of the river in each period, then we can know whether the
water source is used for living, shrimp and fish farming, irrigation,.. or not.

3


Nha Trang city belonging to Khanh Hoa province is one of the most fastdeveloping cities in Vietnam. It is a centre of tourism, resort, services and commercial
transactions of Vietnam and the world. Besides tourism, the city develop many
industries such as seafood processing, garments and port services.
Together with an unstoppable development of economy, environmental quality of
the city has been reduced. Cai River is used for domestic water supply of the city but
the content of suspended matters, organics, and microorganism is higher than
standards of water supply. Water quality in many bridges in the city like Binh Tan,
Sat, Bong,… is seriously polluted by many living households near polluted areas,
especially smell pollution. Domestic waste is an urgent concern of the city. Besides,
the featured thing of Nha Trang is smell pollution from in-shore aquaculture villages.
These pressing problems are preventing from city development. The side-effects of
economic and social development are pollution and damaging natural environment and
living environment.
Economic and social development put pressure under natural resources like soil,
water, air, biological resources,… An increase in waste from many sources like:
domestic waste, production, tourism; waste from aquaculture cages, tourist boats,
waste oil from means of river transport, means of sport transport, untreated waste
water or partially untreated waste water from hotels, tourist attractions, entertainment
areas, factories, living households,…will potentially raise inshore water pollution.
Economic and social development will lead to a change in a purpose of using land for
development activities like the constructions of residential areas, new urban places,
hotels, tourist attractions, mining,… or a decrease in the size of mangroves, natural
land, surface water,… due to deforestation, land reclamation to build sea reclamation
constructions, burning forest for farming,…also increases the depression level of
natural views.
In recent years, there are many researches on the field of proper use of water
resource. Especially, for example:

- The mission of defining cause, range, affecting level of the environment in Ba
Cheo Channel basin, Long Thanh Province, Dong Nai city was executed by Resources
and Environment Institute and Associate Professor, Doctor Nguyen Van Phuoc was a
4


chairman in 2012. The mission evaluated the pollution level and range of water quality
in the river basin affected by waste release of Sonadezi Long Thanh industrial zone
which influences economic activities of the residents [14].
- State research project 08.04 “Research on building the model of integrated
management of resources and the Da river basin environment” was hosted by
Scientific Irrigation Institute and Doctor Nguyen Quang Trung was a chairman in
10/2001 to 9/2004. This project built the record of Da River Basin and the
methodology and proposed 2 models of integrated management of Da River Basin:
Expanded model of planning management of Hong River Basin (legal model) and the
model of integrated management of resources and Da River Basin [15].
- State-levelled topic KC.08.25: “Research on general solutions of reasonable use
of resources and environmental protection of the basins of Ba and Con River was
hosted by Geography Institute and Associate Professor. Doctor Nguyen Van Cu was a
chairman from 1/2004 to 12/2005. The main results were to build up general solutions
of general management aiming at reasonable use of resources and environmental
protection of the basins of Ba and Con River, set up data about natural, resources,
environmental, economic, and social conditions of the basins of Ba and Con River to
help researchers and natural resources managers update information fast and
synchronously on the whole basin [16].
- State-levelled topic KC.08.27: “Research on general solutions of reasonable use
of resources, environmental protection and natural disasters prevention on the basis of
Lo and Chay River was hosted by Hydrometeorology Institute – Resources and
Environment Department and Doctor, researcher La Thanh Ha was a chairman from
1/2004 to 12/2005. The main results were to evaluate the status quo, process of

exploiting and using resources on the basis of Lo and Chay River; environment quality
and environmental catastrophe on the basins; causes and effects of the recession
procedure of resources and environment on basins; propose solutions of reasonable
exploitation and use, environmental protection of Lo and Chay Basin River; set up
database about resources and environment of the basins [17].
- State-levelled topic KC.08.18/06-10 “General management of basin river and
reasonable use of water resources of Dong Nai river system” was hosted by Doctor Do
5


Tien Lanh – Southern Science Institute of Irrigation in 2007 - 2010. The main goals
were to set up a suitable mechanism to share water source to solve conflicts of water
use, operate water reservoir system on the basin and propose practical solutions of
reasonable use and water sources pollution control on Dong Nai Basin River [18].
- Nguyen Van Hop and his assistants used the model NSF- WQI (America) to
evaluate variation water quality of Huong River from 5/1998 to 12/2002 for the
purpose of representative evaluation. From January to December, 2004, they used the
improved method WQI of Bhargava (India) to classify and zone water quality Huong
River as well as other rivers of Quang Tri Province (2005) and Thua Thien Hue
(2006). The results showed that the improved method WQI of Bhargava (India) had
higher sensitivity than the model NSF- WQI (America) [6].
- Ton That Lang applied the method Delphi to inquiry experts’ ideas and used the
model NSF- WQI (America) to set up index water quality serving the practices of
managing and controlling water quality of Dong Nai River system in 2003 – 2005. [12]
- In 2007 – 2008, in the sphere of municipal - levelled “Research on zoning water
quality based on water quality indexes (WQI) and evaluation on water use capability
of rivers, canals in Ho Chi Minh City” of Le Trinh, water quality index was applied
widely to zone water quality rivers, canals in the city based on applying and improving
2 basic models WQI: NSF- WQI (America) and Bhargava (India). The author
proposed 3 water quality models for specific conditions of Ho Chi Minh city (noted

WQI – NSF/HCM, HCM – WQI and WQIB – HCM) with 10 typical indexes (DO,
BOD, SS, total coliform, pH, total N, opaque level, oil, COD, total P), inquiry experts’
ideas and used the method Delphi to set up value. Simultaneously, he calculated the
value of indexes for 35 survey sites in the city [4].
- In 2009, on the basis of Research on setting up water quality indexes (WQI)
serving the practices of planning water sources of Pham Gia Hien [7], WQI was
proposed to be counted :
WQI-2: WQI was based on CCME-WQI but had a change in coefficient.
CCME-WQI was used to calculate annual year, in which WQI-2 was proposed to
calculate a monthly data. If a month has many series of data, the result WQI-2 of a
month is calculated based on the average of these series.
6


WQI  2  100 

F 1M  F 2 M  F 3 M
1.732

In which: F1M, F2M and F3M are coefficients namely F1, F2 and F3 in WQICCME that is changed with applying weight in the formula of these coefficients.
WQI-4: WQI-4 is proposed based on the method of NSF – WQI, in which
diagrams convert data value to secondary index created by comparing with limited
value (standards water qulity are chosen according to use purposes) and weight of
WQI is consulted from experts’ ideas and from many practical comparisons. Proposed
WQI includes 8 parameters: pH, TSS, turbidity, total Nitrogen, BOD5 and coliform.
- In 2009, Topic “Research on defining total daily maximum waste release
serving to set up a release quota in Sai Gon River (from Thu Dau Mot to Nha Be)”
hosted by Nguyen Ky Phung also applied water quality index America (NSF-WQI) to
sort out and evaluate generally about water quality of Sai Gon River [5].

1.2. Imperiousness
Any form/scale of the socio-economic development is always involved in the
exploitation, the use of natural resources and the disposal of waste which is believed to
cause pollution and environmental degradation. Among them, water is an
indispensable resource in every socio-development activity. The increase in population
and the urbanization process together with the formation of more and more industrial
parks, industrial clusters, the industrial production base; the development of tourism
services, waterway transportation, agriculture etc. are the inevitable trends over the
basins.
The Cai River in Nha Trang is one of the three major rivers in Khanh Hoa
province playing an important role in providing fresh water to serve public welfare,
socio- economic development, but it is not out of the mentioned rules, especially the
fact that it flows through big towns and cities such as Nha Trang, Ninh Hoa, Dien
Khanh etc. Currently, due to population growth, development in industry, agriculture,
tourism and services, large amount of waste is released. Yet, the infrastructure in the
areas is inadequate, so untreated sewage is discharged directly into waterways, leading
much more serious environmental pollution, especially in the water surface.
In Khanh Hoa , there is neither research nor special management program
focused at Cai river basin and the river water. Climate change have an increasing
impact on natural, social economic and environmental conditions on Earth. Therefore,
7


it’s necessary to conduct research on current status and to forecast the pollution of the
river water due to the socio-economic development activities under the impact of
climate change to invent premise for construct solutions and limit the impact of water
quality in Cai river.
From the mentioned clues above, the subject “Study on the pollution of Song
Cai River under the impact of climate change and suggestion of remedies for
recovering the water quality” is necessary and practical to implement.

1.3. Natural characteristics
1.3.1. Geographical location
The research area belongs to Dien Khanh district and a part of Nha Trang city,
Khanh Hoa province. Cai River originates from Gia Le mountain which is 1.812 m in
height, flows through Khanh Vinh, Duyen Khanh district and Nha Trang city and then
pours into the sea at Dai Cu Huan. Cai river has 7 estuaries that originate from the
height from 900 to 2000 m but are short, about under 20 km, so the slope is very high,
which causes many falls in the upstream.
The upstream of Nha Trang River has many falls. From the Cho sea mouth and
above, there are Dong Trang, Ong Hao, Da Lua, Nhet, Mong, Vong waterfalls. In the
research area, the number of falls is smaller, however, the part of the river has received
waste release from production, living and many small river branches. The part of Cai
River flows through Dien Khanh province and Nha Trang city is shown in figure 1.1.

Figure 1.1: The map of research area
8


1.3.2. Climate Features
The entire research area is influenced by the climate of Khanh Hoa, so it both has
tropical monsoon and ocean climate, which makes its climate relatively peaceful.
Due to the impact of lower latitudes, specificities of terrain conditions and the
monsoon regime, the climate of Khanh Hoa has other notable features such as short
winter which is less cold (because of being influenced slightly by the extreme tropical
monsoon); hot dry season lasting from 7 to 8 months (because of a strong influence of
South-West monsoon, combined with the terrain causing Foehn effect); rainy season
shifting toward winter and a short rainy season in the dry season (sub-chronic rain).

1.3.2.1. Heat mode

Daily temperatures usually varify from 5°C to 7°C, reaching the highest in 6, 7, 8
and the lowest in 11, 12. High temperature oscillations in the summer months are due
to strong ground radiation reducing low temperatures.
While the hottest month, in the majority of cases, falls in June (45-80 %), in other
cases, it falls in May (20 %). The hot season may begin as early as February, and the
latest month beginning the hot season is March. The season has the first ending in
November, at the latest in December.
Table 1.1. Average temperatures in the years 2012, 2013, 2014, 2015
Temperature (°C)

2012

2013

2014

2015

Average in the year

27.5

27.3

27.1

27.4

Highest month

31.6 (June)

31.0 (May)

29.4 (June)

31.9 (July)

Lowest month

23.1 (January)

23.1 (December)

23.1 (January)

21.1 (January)

6.3

10.8

Thermal amplitude

8.5

7.9
Source: [2]

9

Figure 1.2. The distribution of average temperature in Khanh Hoa province

1.3.2.2. Wind regime
In winter monsoon season (from October, November last year to March, April
next year), north-east directed winds prevail. The frequency of the prevailing wind
direction is approximately 30 %, and up to 60 % in some places with wind directions
focusing on the North and North-East. Some places have northwest wind direction.
Summer monsoon (from May, June to September, October) has the main
component as southwest wind, affecting Khanh Hoa from 2 directions: to the west
when it crosses the arc of mountains, blowing into the plain in the cases of the early
monsoon or strengthened west flows; to the south and south-east when a joint line
changes its direction. In Nha Trang, in the winter months, the percentage of winds
which have speeds of 2 to 5 m/s exceeds 65 %. The figure for the summer months is
rarely less than 55 % and winds which have speeds reaching 5m/s only account for 10
% of cases.
10


1.3.2.3. Mode rain
Like as the climate of Khanh Hoa Province. Nha Trang and Dien Khanh is
divided into two distinct seasons: rainy and dry seasons. The dry season from January
to August, the rainy season usually starts in September and ends in December.
The annual average rainfall from 1,400 mm to 1,800 mm. The rainfall focus of
the four-month rainy season with the average rainfall total for years 1000 - 1200 mm,
accounting for 65-75 % of the annual rainfall. In the dry season, total rainfall is about
350 - 550mm, accounting for 25 - 35 % of the total annual rainfall, particularly in
October and November accounted for 35 % to 45 % of annual rainfall.
Table 1.2. Monthly rainfall (mm)

Year

2010

2011

2012

2013

2014

2015

January

6.0

29.3

23.1

137.8

35.5

15.2

February

21.1

20.7

22.8

40.8

21.9

0.4

March

38.5

49.2

39.6

34.8

50.4

18.2

April

3.5

202.0

27.3

135.6

203.2

22.7

May

60.3

240.1

157.2

95.4

241.3

51.1

June

32.4

45.7

49.5

18.2

46.9

96.8

July

42.0

34.2

16.6

31.5

35.4

52.1

August

10.9

39.8

51.0

80.4

41.0

119.4

September

258.2

206.7

168.1

308.1

207.9

81.0

October

488.6

167.1

482.6

275.0

168.3

160.8

November

355.1

325.1

543.4

733.6

326.3

5956

December

566.5

41.4

3.7

410.4

42.6

176.0

Total

,1.802.5

1,401.3

1,564.9

2,301.6

1,420.7

1,389.3

Source [2]

11


Figure 1.4. The distribution of rainfall in

Figure 1.3. The distribution of rainfall in
the dry season

the rain season

Figure 1.5. The distribution of total annual rainfall in Khanh Hoa Province
12

1.3.3. Features of major rivers and streams in Khanh Hoa Province
The rivers in Khanh Hoa are short and steep overall. The province has about 40
rivers which are 10 km or more in length, forming a thick distribution network of
rivers. Most rivers originate from the western mountains in the province and flow into
the sea to the east. Along the coast, there is an estuary per each 5 to 7 km. This system
is governed by topographical features and climatic conditions. The two largest rivers
are Cai River (Nha Trang) and Dinh River (Ninh Hoa).
Table 1.3. Morphology of rivers and streams in Khanh Hoa

No
1

Name of rivers
and streams
Cai River (Nha
Trang)

2

Cai River (Ninh
Hoa)

Height of
river
sources
m

The length

Basin
area

Average slope of
catchment area

km

km2

%

1,200

79

2,000

3.7

1,300

44

964

24.5

3

Dong Dien River

806

15

83

13.2

4

To Hap River

900

30

298

3.6

5

Thuong River

800

22

142

6

Tra Duc River

900

23

137

7

Can River

800

18

80

8

Trau River

700

26

160

9

Can River

840

14

86

10

Hien Luong River

1,200

18

154

11

Ro Tuong River

900

9,5

60

Source:[2]
1.3.4. Current situation of water resources exploitation
The river basin has a total inflow of approximately 2.078 billion m3 per year.
With a population of about 546,124 people, the average per capita is approximately
3,804 m3 per year, lower than the national average and the average of the world.
According to the world ranking, the country achieving under the 4,000 m3/person /
year is poor in terms of water, so the Cai river basin are is poor in water. However, the

13


problem is that the total flow of 4 months in flood season (September -Decmber)
accounts for 65 - 66 % of annual flow, and the flow of 8 months in dry season
(January-August) only constitutes 34 - 35 % of annual flow. Compared with the
demand for water, the flow distribution between the two seasons as above is uneven
and very detrimental to production.

1.4. Economic and social characteristics
1.4.1. Population and population distribution
The rate of average annual population growth in 2012 - 2013 is 1.06 % per year.
In 2013, the population in the research area is 60.885 people with females accounting
for 50.5 %. The average population density is 205 people/km2. In which the population
in the research area is shown in Table 1.4.
Table 1.4. Population in the research area in 2014
Dien Khanh province

Nha Trang city

Population
Population

%

Population

%

Total

54,160

100

6,725

100

Male

26,971

49.8

3,315

49.3

Female

27,189

50.2

3,410

50.7

Source: [1]
1.4.2. Economic growth
In terms of economic-social development, Dien Khanh district and Nha Trang
City has continued making efforts, striving to promote its potentials and strengths of
the province, and achieving positive achievements. Especially, Nha Trang city has
remained a strong development of tourism services.
Economic growth rate reaches an annual average of 7.2 %; the economic
structure shifts towards an increase in the share of services - tourism, industry construction. Service and commerce industries are invested to develop with an average
increase of 12.6 %/year; total retail sales of goods and services in 2015 reached 25,488
billion, increasing by 82 % compared to 2011. The facilities and the quality of tourism
services are better and better than the needs of travelers in and out country.

14