Tài liệu Application of swat model to assess the impact of land use changes on stream discharge in nghing tuong watershed, thai nguyen province

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. ii 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 iv 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 v 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 vi 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 ix 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 xi 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? 4 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; 9