THAI NGUYEN UNIVERSITY
UNIVERSITY OF AGRICULTURE AND FORESTRY
DINH NGOC HUAN
TOPIC TITLE: “APPLICATION OF SWAT MODEL TO ASSESS THE
IMPACT OF LAND-USE CHANGES ON STREAM DISCHARGE IN
NGHINH TUONG WATERSHED, THAI NGUYEN PROVINCE”
BACHELOR THESIS
Study Mode: Full-time
Major: Bachelor of Environmental Science and Management
Faculty: International Training and Development Center
Batch: 2010 - 2015
Thai Nguyen, January 2015
DOCUMENTATION PAGE WITH ABSTRACT
Thai Nguyen University of Agriculture and Forestry
Degree Program
Bachelor of Environmental Science and Management
Student name
Dinh Ngoc Huan
Student ID
DTN1054110040
Thesis Tittle
Application of SWAT model to assess the impact of
land-use changes on stream discharge in Nghinh
Tuong watershed, Thai Nguyen Province
Suppervisor (s)
Phan Dinh Binh, Ph.D.
Abstract:
The purpose of this research is to implement “Soil and Water Assessment Tool
(SWAT)” model and GIS to evaluation, assessment impact of land-use changes
on stream discharge in Nghinh Tuong watershed (riverhead Cau river watershed)
in Northern Viet Nam. The watershed were cover by 56% forestry land, 30%
agricultural land, and remain for others. Stream discharge observed data 2002 2012 were used for calibration (2002 - 2007) and validation (2008 - 2012). The
result shown that two coefficients (NSE and PBIAS) to evaluate model
performance were 0.76 and 6.54% for calibration period and 0.87 and 4.74%,
respectively. Stream discharge strongly depends not only on quantity of
precipitation but also on land use change. Through the scenario 1, agricultural
land (corn, orchard and tea) increases 9782.67 ha (2.45%), meanwhile forest
(forest-mixed) decreases 1091.77 ha (2.75%) as compared to baseline scenario.
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Additionally, precipitation increases 3.74% in mean wet season, but decreases
0.5% in mean dry season with respect to baseline period. SWAT model was able
to simulate stream discharge and sediment yield for Nghinh Tuong watershed
successfully not only for Baseline scenario but also for Scenario 1. In brief,
SWAT proves its ability in simulation stream discharge and sediment yield in
watershed level. It is a useful tool to assist water quantity and quality
management process in Nghinh Tuong watershed.
Keywords:
Key words: stream discharge, watershed, GIS, SWAT
model, scenario
Number of pages:
50
Date of Submision :
January 15, 2015
iii
ACKNOWLEDGEMENT
First and foremost, I wish to express my sincere thanks to the boards of
Thai Nguyen University of Agriculture and Forestry, Dean of Faculty Natural
Resources Management, Department of Remote sensing and Surveying of Thai
Nguyen University of Agriculture and Forestry for providing me all the
necessary facilities and all the teachers who built me the scientific knowledge to
complete this research. In particular, I would like to thank my principal research
adviser Dr. Phan Dinh Binh who guided me wholeheartedly when I implement
this research project.
I place on record, my sincere gratitude to all staffs, government and
people in Nghinh Tuong commune Vo Nhai district and Van Lang commune
Dong Hy district, Thai Nguyen province for their expert, valuable guidance
and generous support to our project.
Finally yet importantly, I take this opportunity to express our deepest
appreciation to our families, relatives, friends and fellow students in class of
K42-Advanced Education Program who encouraged and supported me
unceasingly and all who, directly or indirectly, have lent their helping hand in
this venture.
Thank you very much!
Thai Nguyen, January 15, 2015
Student
Dinh Ngoc Huan
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TABLE OF CONTENTS
ACKNOWLEDGEMENT ................................................................................. iv
TABLE OF CONTENTS .................................................................................... v
LIST OF TABLES ............................................................................................ viii
LIST OF FIGURES ............................................................................................ ix
LIST OF ABBREVIATIONS ............................................................................. xi
Part 1: INTRODUCTION .................................................................................. 1
1.1. Research rationale .......................................................................................... 1
1.2. Research’s objectives...................................................................................... 1
1.3. Research questions and hypotheses ................................................................ 3
1.4. Limitations ...................................................................................................... 3
1.5. Definitions ...................................................................................................... 3
Part 2: LITERATURE REVIEW ...................................................................... 5
2.1. Research situation ........................................................................................... 5
2.2. Soil and Water Assessment Tool (SWAT) Model ........................................... 6
2.2.1. Concept of SWAT ........................................................................................ 6
2.3. SWAT Theory ................................................................................................. 8
2.3.1. SWAT hydrologic component...................................................................... 8
2.3.2. The land phase of the hydrologic cycle ....................................................... 8
2.3.2.1. Climate...................................................................................................... 9
2.3.2.2. Hydrology ................................................................................................. 9
2.3.3. Routing phase of the hydrologic cycle ...................................................... 10
2.3.3.1. Routing in river....................................................................................... 10
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2.3.3.2. Routing through reservoirs ..................................................................... 10
2.3.3.3. Sediment routing .................................................................................... 10
2.4. Component processes in model (Neitsch et al., 2005a) ............................... 11
2.4.1. Surface runoff ............................................................................................ 11
2.4.2. Underground Flow ..................................................................................... 13
2.4.2.1. Lateral subsurface flow .......................................................................... 13
2.4.2.2. Underground flow................................................................................... 13
2.5. SWAT sediment component (Neitsch et al., 2005a) .................................... 14
2.5.1. The Modified Universal Soil Loss Equation (MUSLE)............................ 14
Part 3: METHODS ............................................................................................ 16
3.1. Materials ....................................................................................................... 16
3.1.1. Description and topography ...................................................................... 16
3.1.2. Climatic characteristics ............................................................................. 18
3.2. Methods ........................................................................................................ 19
3.2.1. Watershed delineation ............................................................................... 19
3.2.2. Soil classification and soil physical characteristics ................................. 19
3.2.3. Land cover classification .......................................................................... 20
3.3. SWAT model ................................................................................................. 20
3.4. SWAT model performance evaluation ......................................................... 22
Part 4: RESULTS ............................................................................................. 25
4.1. Overview of Nghinh Tuong basin ................................................................ 25
4.2. Preparation input data .................................................................................. 26
4.2.1. Climatic parameters................................................................................... 26
4.2.1.1. Precipitation ............................................................................................ 29
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4.2.1.2. Stream discharge..................................................................................... 31
4.2.2. Spatial databases ........................................................................................ 33
4.3. Land use scenarios ........................................................................................ 36
4.3.1. Baseline scenario (2012) ........................................................................... 36
4.3.2. Scenario 1 (2020) ...................................................................................... 37
4.3.3. Scenario 2 (2030) ...................................................................................... 37
4.4. Assessing the impact of land-use changes on stream discharge in Nghinh
Tuong watershed, Thai Nguyen Province ........................................................... 41
4.4.1. Baseline scenario ....................................................................................... 41
4.4.2. Land use scenario 1 (2020) ....................................................................... 45
4.4.3. Land use scenario 2 (2030)........................................................................ 47
Part 5: CONCLUSIONS AND DISCUSSION ................................................ 49
5.1. Conclusions .................................................................................................. 49
5.2. Discussion ..................................................................................................... 50
REFERENCES .................................................................................................. 52
vii
LIST OF TABLES
Table 4.1. Summarized climatic characteristics (1983- 2012) of Nghinh Tuong
watershed for SWAT simulation ............................................................ 27
Table 4.2. Total monthly precipitation in Nghinh Tuong watershed from 1983 to
2012.(mm)................................................................................................ 30
Table 4.3. Observed monthly stream discharge at Nghinh Tuong outlet from 2002
- 2012 (m3/s) ........................................................................................... 32
Table 4.4. Sub-watershed characteristics of Nghinh Tuong watershed ................ 35
Table 4.5. Sub-outlet’s characteristics of Nghinh Tuong watershed .................. 36
Table 4.6. Land use scenarios for Nghinh Tuong watershed ................................ 39
Table 4.7. Observed and simulated stream discharge for each period in Nghinh
Tuong watershed ..................................................................................... 42
Table 4.8. Coefficients of monthly NSE and PBIAS as calibrating and validating
stream discharge ..................................................................................... 44
Table 4.9. Stream discharge of Scenarios 1 (2020) and Baseline scenario in
Nghinh Tuong watershed (m3/s) ............................................................. 46
Table 4.10. Stream discharge of Scenarios 2 (2030) and Baseline scenario in
Nghinh Tuong watershed (m3/s) ............................................................. 47
viii
LIST OF FIGURES
Figure 3.1: Map of Vo Nhai District ..................................................................... 18
Figure 3.2. SWAT soil database builder schematization. .................................... 20
Figure 3.3. Application of SWAT on Nghinh Tuong watershed for simulation
stream discharge and sediment load ...................................................... 22
Figure 4.1: The position of Nghinh Tuong basin ................................................. 25
Figure 4.2. Monthly maximum, minimum and average temperature in Nghinh
Tuong watershed from 1983 to 2012 ......................................................... 28
Figure 4.3. Monthly relative humidity in Nghinh Tuong watershed from 1983
to 2012 .................................................................................................... 28
Figure 4.4. Monthly wind speed in Nghinh Tuong watershed from 1983 to 2012 ... 29
Figure 4.5. Total monthly precipitation in Nghinh Tuong watershed from 1983
to 2012 .................................................................................................... 31
Figure 4.6. Observed monthly stream discharge at Nghinh Tuong
outlet from 2002 - 2012 ......................................................................... 32
Figure 4.7. Digital elevation model (DEM) and stream network of Nghinh Tuong
watershed ............................................................................................... 33
Figure 4.8. Map of land use status Nghinh Tuong River basin in 2012 ............... 34
Figure 4.9. Soil map of Nghinh Tuong River basin in 2012 ................................ 34
Figure 4.10. Sub-watershed and stream network of Nghinh Tuong watershed ... 35
Figure 4.11. Map of Baseline Land use scenario (2012) for Nghinh Tuong
watershed ............................................................................................... 40
Figure 4.12. Map of Land use scenario 1(2020) for Nghinh Tuong watershed ... 40
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Figure 4.13. Map of Land use scenario 2 (2030) for Nghinh Tuong watershed . 41
Figure 4.14. Observed versus simulated monthly stream discharge and
precipitation of Nghinh Tuong watershed during calibration and
validation periods ................................................................................... 43
Figure 4.15 .Observed versus simulated average monthly stream discharge during
calibration and validation periods of Nghinh Tuong watershed ............ 44
Figure 4.16. Locations of land use change for scenario 1 (2020) for Nghinh
Tuong watershed .................................................................................... 45
Figure 4.17. Locations of land use change for scenario 2 (2030) for Nghinh
Tuong watershed .................................................................................... 47
x
LIST OF ABBREVIATIONS
SWAT
: Soi water assessment tool
CEAP
: Conservation Effects Assessment Projects
GIS
: Geographic information system
ARS
: Agricultural Research Service
DEM
: Digital Elevation Model
SWt
: The sum of water vapor at the end of measurement (mm);
SWo
: The sum of initial water volume at day I (mm);
T
: Time (day);
Rday
: The total rainfall at the day i (mm)
Qsurf
: The sum of surface water of the day i (mm);
Ea
: Water vapor amount at the day i (mm)
Wseep
: The amount of water penetrating underground layer;
Qgw
: The amount of recurrent water at the day i (mm)
SCS
: Soil Conservation Service
Ia
: The initial abstractions which includes surface storage,
interception and infiltration prior to runoff (mm H2O),
S
: The retention parameter (mm H2O).
CN
: Curve number
HRU
: Hydrologic Response Unit
HSG
: Hydrologic Soil Group
USGS
: United States Geologic Survey
NSE
: Nash-Sutcliffe efficiency
USDA
: The United States Department of Agriculture
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PART I. INTRODUCTION
1.1. Research rationale
Nghinh Tuong is the upland stream of Cau river in which supplies water for
domestic, agriculture and industrial sectors in Thai Nguyen. It is a vital resource
for any human activities and living. However, the river basin has been affected
seriously by the economic growth caused the pollution and depletion clean water
resources, and extremely climate events as drought and flooding. If we do not have
appreciated solution for protecting the resources, we have to pay an expensive cost
in the near future.
On the other hand, the intensive agriculture, overexploitation heavy metals as
well as deforestation have lately been raising many problems in this basin. The
farmers cultivate agricultural crops, (especially in slope land) and overuse of
pesticides and fertilizers for crops, which makes not only soil erosion but also
pollutants load on stream into downstream. Nevertheless, there have been no
comprehensive assessments of land use change impact in this river basin. Hence, a
modeling effort to simulate these problems in Nghinh Tuong watershed should be
implemented. Under these circumstances, we proposed the research project
“Application of SWAT model to assess the impact of land-use changes on
stream discharge in Nghinh Tuong watershed, Thai Nguyen Province”
1.2. Research’s objectives
The rapid economic growth has affirmed that Thai Nguyen is a major
social and economic center of the Northern midland and mountainous area of
Vietnam. On the flip side however, the environment has suffered the degradation,
exposed the population to serious air and water pollution, including watershed
1
degradation. The cause of the watershed degradation is mainly due to
overexploitation of natural resources and land use change.
Nghinh Tuong watershed located in Vo Nhai district, Thai Nguyen
province is a sub-basin of Cau river basin, which is the biggest river basin in Viet
Nam. Its estimated length is 46 km, and it drains an area of 397 km2, discharging
thousands of ha irrigation demand annually for people in Nghinh Tuong
commune (NTPC, 2010). Approximately 40% of the river's length travels the
limestone walls, valleys and steep cliffs, especially, passes through Than Sa
protected areas which has been containing diverse of rare plant and animal
species. Since the economic renewal campaign (Doi Moi), most of areas in the
river basin have been converted to other farming land types and levels, which
bring more economic benefits. On the other hand, deforestation and intensive
agricultural land practices put a high pressure on land. In addition, recently the
illegal extraction of sand, gravel, gold and forest production have impacted
broadly on environment, water quantity and quality which leads to soil erosion,
degradation, sediment and nutrient deposition in this river basin.
The recent studies showed that water discharge depends not only on the
precipitation, but also on land use types. Gassman et al, (2007) stated that water
discharge based on proportion of arable land and forested land in the basin. Once
the water discharge increases, it leads to the step-up of soil erosion rate, reduction
of soil fertility and downstream flooding during the rainy season. Furthermore, the
soil loss can transport pollutants in land as pesticides, heavy metals, waste to
downstream basin causing seriously impact on the living environment of aquatic
species and human health (Ella, 2005), especially in dry season.
2
This study are (1) to apply (SWAT) model in a small watershed in Thai
Nguyen to assess the long-term impact of land-use changes on stream discharge;
(2) to understand the behavior of the river based on land use types; and (3) to
provide appropriate suggestions to sustain the soil and water resources.
1.3. Research questions and hypotheses
How do the intensive agriculture, overexploitation heavy metals as well
as deforestation have lately been raising many problems in Nghinh Tuong basin ?
What is the modeling effort to simulate these problems in Nghinh Tuong
watershed?
The application of SWAT model-Soil and Water Assessment Tools understand
the effect of land-use changes on stream discharge and prove its ability in
simulation stream discharge in watershed level and then provide appropriate
suggestions to sustain the soil and water resources.
1.4. Limitations
The Application of SWAT model is very large. However, the input data
requirements for models and need much time to process the data, the input data
requirements for models and need much time to process the data. To be able to
use this model to quantitatively assess the impact of the floods forest necessarily
have a uniform data input the model was validated for stream discharge and
sediment yield at main outlet, but not yet validated for sub-outlets due to the
limited data.
1.5. Definitions
Nowadays, the land use changes impact assessment on stream discharge in
Nghinh Tuong watershed using SWAT model and GIS techniques has been
3
carried out as a powerful strategy for local managers. The simulation of the
impact of land-use changes on stream discharge in upland watershed has been
determined through hydrological models like SWAT model-Soil and Water
Assessment Tools (Arnold et al, 1999). The goals of this study are to understand
the effect of land-use changes on stream discharge and prove its ability in
simulation stream discharge in watershed level and then provide appropriate
suggestions to sustain the soil and water resources. Successfully completing this
study helps to provide a technical approach in assessing the long-term impact of
land-use changes on stream discharge and orient the appreciate strategies for
local government in sustaining the soil and water resources. Furthermore, it
would allow locally adjusted land use orientation and environment protection,
hence minimizing the consequences of climate change. By implementing this
study allows students to enhance their practical knowledge and gain
experiences for their careers?
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PART II. LITERATURE REVIEW
2.1. Research situation
SWAT model (Arnold et al, 2000) have been officially proven as an
effective tool to assess water resources and pollution to large scopes and globally
environmental conditions. Also, an increasing number of researchers pay
attention to the capabilities of SWAT in predicting nutrient as well as sediment
loads which is benefit able for agricultural productions and environmental
protection. In United State, SWAT is being progressively used to support the
general analysis of largest load volume day (Bo-rah et al, 2006), effective
researches of activities of ecology conservation in USDA Conservation Effects
Assessment Projects, fulfilling the assessment to large areas such as Mississippi
upstream river and whole United State (Arnold et al 1999; Jha et al, 2006) and
many applications in assessing water and land use quality. Moreover, Arnold et
al. (1999) evaluated stream flow and sediment yield data in the Texas Gulf basin
with drainage areas ranging from 2,253 to 304,260 km2. Stream flow data from
approximately 1,000 stream monitoring gauges from 1960 to 1989 were used to
calibrate and validate the model.
Currently, In Vietnam, GIS and Remote Sensing application in
environmental monitoring is strongly motivated orderly aiming to detect, assess
and predict contaminated levels for specific regions to issue then solutions
quickly and effectively. However, in fact, results of GIS application and SWAT
model are still limited. In 2009, Nguyen Kim Loi have successfully used SWAT
model to assess the affection of Agro-Forestry systems to streamflow and
sediment load at Nghia Trung watershed, Dong Nai upstream river. Otherwise,
5
Phan Dinh Binh et al (2011b) have published his researched results with the
success of using SWAT model to assess affections of climate changes and
deforestation to streamflow and sediment yield at Phu Luong River and other
successful researches. In summary, SWAT application has been initially brought
out successful outcomes which create indirectly new development steps for
technology application in Vietnam.
2.2. Soil and Water Assessment Tool (SWAT) Model
2.2.1. Concept of SWAT
SWAT acronyms for Soil and Water Assessment Tool, a river basin, or
watershed, scale model developed by Dr. Jeff Arnold for the USDA Agricultural
Research Service (ARS). SWAT was developed to predict the impact of land
management practices on water, sediment and agricultural chemical yields in
large complex watersheds with varying soils, land use and management
bconditions over long periods of time. To satisfy this objective, the model +) is
physically based rather than incorporating regression equations to describe the
relationship between input and output variables, SWAT requires specific
information about weather, soil properties, topography, vegetation, and land
management practices occurring in the watershed. +) is computationally efficient.
Simulation of very large basins or a variety of management strategies can be
performed without excessive investment of time or money. +) enable users to
study long-term impacts. Many of the problems currently addressed by users
involve the gradual buildup of pollutants and the impact on downstream water
bodies. Notice that SWAT is a continuous time model, i.e. a long-term yield
model not designed to simulate detailed, single-event flood routing.
6
The Input and Output Data of SWAT model:
a) The input data of model
Required to express in 2 kinds of data: attribute and spatial data
Spatial data in map form includes:
- DEM - Digital Elevation Model
- Landuse map
- Soil map
- Map of river, stream, and lake networks in area
Attribute data under Database comprises:
- Meteorological data including air temperature, radiation, wind speed, and
rainfall
- Hydrological data including Streamflow, sandy concentration, lake
volumes etc.
- Soil data including soil types, characteristics and features of each soil layer
- Data of crops in researched area, growth rate etc.
- Data of fertilizers applied in cultivated areas
b) The output data
Assessing water quality and quantity;
Assessing the amount of mud, sands in streamflow;
Assessing processes of cultivation through nutrient cycle;
Assessing watershed management;
7
2.3. SWAT Theory
2.3.1. SWAT hydrologic component
Water balance is the driving force behind everything that happens in the
watershed. To accurately predict the movement of pesticides, sediments or
nutrients, the hydrologic cycle as simulated by the model must conform to what
is happening in the watershed. Simulation of the hydrology of a watershed can be
separated into two major divisions. The first division is the land phase of the
hydrologic cycle that controls the amount of water, sediment, nutrient and
pesticide loadings to the main channel in each sub basin. The second division
is the water or routing phase of the hydrologic cycle which can be defined as the
movement of water, sediments, etc. through the channel network of the
watershed to the outlet.
2.3.2. The land phase of the hydrologic cycle
Hydrologic cycle is simulated by SWAT model basing on water
balance equation:
SWt = SWo +
Rday - Qsuf - Ea - Wseep - Qgw)
Where
SWt is the sum of water vapor at the end of measurement (mm);
SWo is the sum of initial water volume at day I (mm);
T is time (day);
Rday is the total rainfall at the day i (mm)
Qsurf is the sum of surface water of the day i (mm);
Ea is water vapor amount at the day i (mm)
Wseep is the amount of water penetrating underground layer;
8
Qgw is the amount of recurrent water at the day i (mm)
The subdivision of the watershed enables the model to reflect differences
in evapotranspiration (ET) for various crops and soils. Runoff is predicted
separately for each hydrology response unit (HRU) and routs to obtain the total
runoff for the watershed. This increases accuracy and gives a much better
physical description of the water balance.
2.3.2.1. Climate
The climate of a watershed provides the moisture and energy input that
controls the water balance and determines the relative importance of the different
components of the hydrologic cycle. The climatic variables required by SWAT
consist of daily precipitation, maximum/minimum air temperature, solar
radiation, wind speed and relative humidity. The model allows values for daily
precipitation, maximum/ minimum air temperatures, solar radiation, wind
speed and relative humidity to be input from records of observed data or
generated during the simulation.
2.3.2.2. Hydrology
Precipitation may be intercepted and held in the vegetation canopy or falls
to the soil surface. Water on the soil surface will infiltrate into the soil profile or
flow overland as runoff. Runoff moves relatively quickly toward a stream
channel and contributes to short-term stream response. Infiltrated water may be
held in the soil and later evapotranspiration or it may slowly make its way to the
surface-water system via underground paths. Furthermore, hydrologic calculation
in the model includes: +) routing phase of underground paths; +) calculating loss;
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