STUDY ON CONJUNCTIVE USE OF GROUNDWATER AND SURFACE WATER FOR PADDY RICE IRRIGATION IN SANJIANG PLAIN NORTHEAST CHINA

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1 STUDY ON CONJUNCTIVE USE OF GROUNDWATER AND SURFACE WATER FOR PADDY RICE IRRIGATION IN SANJIANG PLAIN NORTHEAST CHINA Zhanyi GAO 1, Jing LIU 1,2, ShaoliWANG 1, Haorui CHEN 1, Yongqing ZHAO 3, and Chengkun YU 4 ABSTRACT Most of the paddy rice in Sanjiang Plain is irrigated with groundwater. In recent years water requirement is increasing with the rapid increase of paddy field while groundwater table is falling continually. In order to maintain sustainable development of water resources in the region in the long term, comprehensive measures, including conjunctive use of surface and groundwater and water saving practices should be jointly applied. To investigate these comprehensive measures a study on conjunctive use of groundwater and surface water for paddy rice irrigation in the region has been implemented since 214. This paper presents the water management scenarios for the region based on the study by adopting various water-saving irrigation technologies and measures, volume of reused water, and application of groundwater and surface water. A semi-distributed water balance model was developed to simulate water cycle at irrigation district level factors so as to analyse water use efficiency and dynamic groundwater response to various scenarios. Based on this study, reasonable water use modes under different hydrological years are proposed. These modes show how and when to use groundwater, surface water and return flow. The outcome of the study can also be used to provide theory basis for the optimal allocation of regional water resources. Keywords:, surface water, water reuse, water use efficiency, paddy irrigation 1. INTRODUCTION Located in Hei Longjiang Province in Northeast China Sanjiang Plain is an important grain production area. It covers an area of km 2. Paddy rice is the dominant crop grown in 3.51 million ha. This area is highly dependent on groundwater resources for irrigation. With the increase in paddy area, water demand is increasing and the groundwater table is falling continually due to over-exploitation. Utilization of groundwater and surface water is unequal. Many studies have been carried out to investigate conjunctive use of groundwater and surface water in sustainable manner. Hanson et al. (21) used an integrated model to assess water demands and water supply from rainfall, groundwater, and surface water. Some researchers indicated that the water use efficiency could be improved by integrated management of surface and groundwater (Chowdary et al. 23; Chowdhury et al. 29; Srivastava et al. 216). 1 State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 138,China; gaozhy@iwhr.com 2 College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 2198, China; jing83694@163.com 3 Jiansanjiang Water Administration Bureau, Heilongjiang Land Reclamation Bureau, Fujin , China; JSJSZDD@sohu.com 4 Qianjin Water Administration Bureau, Qianjin Farm, Heilongjiang Land Reclamation Bureau, Fujin , China; @qq.com 1

2 There are many hydrological models to simulate water cycle process, such as MIKE- SHE (Abbott et al. 1986), SWAT (Arnold et al. 1998) and WEP (Jia et al. 26). However, these models are mainly applied to natural watershed. As such, they cannot simulate water cycle in an irrigation district with complicated irrigation and drainage conditions. Thus a semi-distributed water balance model was developed to quantify water cycle factors of the hydrological process in rice growing areas. The model was validated by using the data of groundwater tables and river discharges. Then the validated model was employed to evaluate different water management scenarios comprising change in irrigation type, water reuse volume, groundwater use proportion, and impact of canal lining. The core goal of the study is to keep sustainable utilization of groundwater and improve the regional water use efficiency. 2. MATERIALS AND METHODS 2.1 Natural condition in the study area The BLH River watershed was selected as the study area (Figure 1). It is located in Northeast of Sanjiang Plain. The area comprised mainly Qian Jin Farm, Chuang Ye Farm, Qi Xing Farm, and Hong Wei Farm, covering an area of km 2. With continental monsoon climate, it is warm and wet in summer and cold in winter. Average annual precipitation is mm. About 5~7% of the rainfall is concentrated in July, August and September. The distribution is uneven in the year. The annual average temperature is 2.2 C with annual sunshine time about 226 to2429 h. The annual frost-free period is about 12~141 d. Average annual evaporation is 123 mm and the annual average humidity is 68%. is the main water source for irrigation in this area. The groundwater table is about 13~14 m below the surface in 215 and it is declining year by year. 2.2 A water balance model Figure 1. Location of the study area A semi-distributed water balance model was developed to simulate water cycle factors such as evapotranspiration, deep percolation, daily ponding depth in the field, groundwater recharge, drainage, groundwater table, etc. The model was calibrated and validated by using data collected from field experiments. The groundwater tables 2

3 of 14 wells and river discharges in three cross-sections in BLH River were measured. The observing frequency of groundwater tables were once a day. The river discharges in three cross-sections in BLH River were derived through the dischargestage relations of each cross-section Model formulation The model assumes that components of water cycle, such as evapotranspiration, infiltration, etc. are separate, sequential processes; water flows vertically downward under gravity; only the area of different land use types are considered in simulation unit, there is no spatial position for land use. Structure of the developed model is shown in Figure 2. In horizontal, the study area was divided into three kinds of simulation units, including basic simulation unit, channel unit, and drains/river unit. A basic simulation unit can be subdivided into several water cycle units on the basis of land use types, soil types and hydrogeological parameters. Land use types mainly considered the paddy field, grassland, dry land, bare land, and habitation. The water balance sub-model of each water cycle unit can be established respectively as well as the channel unit and drains/river unit. In vertical, taking the paddy field unit as example, it can be divided into four layers. They are surface reservoir, root zone, transition zone, and aquifer. The transition zone could be subdivided into two layers (the clay loam layer and loamy sand layer) according to the soil texture. Hydraulic connection could be established between each water cycle unit through the drains and groundwater lateral exchange. In Figure 2 evaporation 1 and evaporation 2 stand for water surface and soil evaporation respectively. Paddy field Water storage Study Area Basic simulation unit Evaporation 1 Channels unit Grassland Dry land Bare land Habitation Seepage Surface water Irrigation Surface reservoir Root zone Precipitation Infiltration Transition zone Evaporation 1 Drainage Evaporation 2 Transpiration Distribute water Evaporation 1 Phreatic evaporation Recharge Lateral exchange Drains/River unit Exchange Drainage Figure 2. Structure of the water balance model The generalized water balance equations of drains/river unit and each layer of the basic simulation unit at daily scale are shown as follows. 3

4 Surface reservoir The water balance equation of surface reservoir is: SPt SPt 1 Pt IRt ETt St DRt (1) Where SP t= water ponding depth in rice field on tth day (mm), SP t-1 = water ponding depth in rice field on t-1 th day (mm), P t = precipitation (mm), IR t = amount of irrigation water (mm), ET t = crop evapotranspiration (mm), which can be calculated by Penman-Monteith equation and crop coefficients, S t = amount of water lost through percolation (mm), DR t = drainage through paddy levee (mm), which will only occur when the ponding depth in the field exceeds the dike height. Amount of irrigation water. For rice crop, the amount of irrigation water is computed according to the irrigation system. In the region three irrigation water sourcesviz, reuse water, groundwater and surface water could be used and the utilization of reuse water is given priority. If the reuse water cannot satisfy the irrigation water requirement, groundwater and surface water will be used based on the groundwater use proportion. Amount of water lost through percolation.the amount of water lost through percolation is calculated by empirical formula (Shi et al. 213) on the assumption that the amount has linear relation with the water ponding depth. In equation 2 both a and b are fitting parameters which can be fitted by field experiment data. S a SP b t t (2) Root zone and transition zone Storage capacity is defined as the water capacity when the soil water content reaches saturation moisture content in root zone and transition zone. If the soil water content exceeds the storage capacity, the extra amount would be allocated to the next zone. In this model, restrictive permeability coefficient has been applied to calculate the infiltration process between the field capacity and saturation moisture content of each zone. Thus the water transported to the next zone would be allocated layer by layer with the same rules until the water flows into the aquifer. The amount of water flowing into the aquifer is considered to be groundwater recharge. system The groundwater table can be calculated by the following equation. swt DPt DP t 1 swt ( Rgt + Wlat Wpet Wpt ) A (3) Where DP t = groundwater table on t th day (m), DP t-1 = groundwater table on t-1 th day (m), Δsw t= the variation in groundwater storage (m), μ = specific yield of the aquifer, which is measured by pumping test in the region, Rg t= groundwater recharge of each basic simulation unit (m 3 ), including the recharge of field, channel, drains and river, Wla t = groundwater lateral exchange with other basic simulation units (m 3 ), which is computed on the basis of Darcy law, Wpe t = phreatic evaporation (m 3 ),Wp t = the amount of water pumping (m 3 ), A = area of the basic simulation unit (m 2 ). 4

5 Phreatic evaporation.phreatic evaporation will only occur when the groundwater depth in the field is less than the critical depth of groundwater evaporation, and it can be calculated by the following equation. h wpe (1 t ) n t KC E t h (4) Where wpe t = phreatic evaporation (mm), Kc = crop coefficient, E t = water surface evaporation (mm), h t = the groundwater depth (m), h = the critical depth of groundwater evaporation (m), n = empirical coefficient, generally ranging from 1 to 3. Drains/river unit The water balance equation of drains/river unit is: Vt Vt 1 Vint Vpt IrVt Vet Vst Vdt (5) Where V t = drains/river storage on t th day (m 3 ), V t-1 = drains/river storage on t-1 th day (m 3 ), Vin t = flow into the drains/river (m 3 ), which equals to the amount of drainage from the upper level, Vp t = precipitation into the drains/river (m 3 ), IrV t = the amount of reuse water from drains/river (m 3 ), Ve t = surface water evaporation of the drains/river (m 3 ), Vs t = the amount of seepage (m 3 ),Vd t = drainage of the drains/river (m 3 ). The amount of reuse water.the amount of reuse water from drains/river is determined by the reuse proportion (r v), and it can be calculated by the following equation. IrVt rv Vt (6) Drainage of the drains/river.drainage of the drains/river is determined by the interception coefficient (cv), and it can be calculated by the following equation. Vdt (1 cv ) Vt (7) Model inputs The model inputs mainly include the following aspects: (i) (ii) (iii) (iv) (v) Climatic data on daily basis: the maximum, minimum and average temperature; rainfall; relative humidity; average wind speed; sunshine hours; atmospheric pressure. Soil parameters: depth, field capacity and saturation moisture content of different layers. Hydrogeological parameters: specific yield and hydraulic conductivity of different layers. Basic information of channel, drains and river: length, cross-section information, the utilization coefficient of the channel. Cropping and other information: crop coefficient and land use area of each basic simulation unit. 5

6 River discharge (1 4 m³) Rainfall (mm) River discharge (1 4 m³) Rainfall (mm) table(m) table (m) table (m) table (m) 2 nd World Irrigation Forum (WIF2) Model calibration and validation Model calibration The groundwater tables of 14 wells and river discharges in three cross-sections in BLH River were selected for model calibration. The location of 14 wells and three cross-sections in BLH River were shown in Figure 1. These calibration data were measured during the rice growth period in 215. The comparison of observed and simulated groundwater tables of 4 selected wells and river discharges in two selected cross-sections for model calibration were shown in Figure 3 and Figure 4 respectively QJ QJ /1 5/1 6/1 7/1 8/1 9/1 47. HW /1 5/1 6/1 7/1 8/1 9/1 45. HH /1 5/1 6/1 7/1 8/1 9/1 Date (month/day) 42. 4/1 5/1 6/1 7/1 8/1 9/1 Date (month/day) Figure 3. The comparison of observed and simulated groundwater tables in Rainfall B Rainfall B /1 5/1 6/1 7/1 8/1 9/1 Date (month/day) 6 4/1 5/1 6/1 7/1 8/1 9/1 Date (month/day) 6 Figure 4. River discharges in two selected cross-sections in BLH River in 215 Three statistical parameters, including the coefficient of determination (R 2 ), relative error (RE), and Nash-Sutcliffe efficiency coefficient (Nash and Sutcliffe, 197; Saleh et al. 2; Zhang 25; Wang and Cui 211) were selected to evaluate the model in calibration period. The coefficient of determination with range from to 1 is a statistical measure on how well the regression line approximates the real data points. 6

7 table (m) table (m) 2 nd World Irrigation Forum (WIF2) The greater the coefficient of determination, the better regression line fits the observed data. Relative error represents the relative change between the simulated and the observed data. It is usually expressed as percentages, and it ranges from to 1%. Nash Sutcliffe efficiency coefficient ranges from to 1. An efficiency of 1 corresponds to a perfect match of simulated values to the observed data. Assessment standard of the simulation efficiency index were shown in Table 1 and the evaluation results were in Table 2. From Table 2 we can get the conclusion that the model did a somewhat better job in calibration period. Table 1. Assessment standard of the simulation efficiency index Assessment standard Coefficient of determination Relative error (%) Nash-Sutcliffe efficiency coefficient Excellent.95-5~5 1.~.8 Good.94~.8 Fair.79~.7-1~-5 or 5~1-2~-1 or 1~2.79~.6.59~.4 Poor <.7 >2 or <-2 <.4 Table 2. Evaluation of the simulated results of model calibration Statistical parameters Determination coefficient Relative error (%) Nash-Sutcliffe efficiency coefficient table.92 (Good).44 (Excellent).88 (Excellent) River discharges.76 (Fair) (Good).71 (Good) Model validation After calibration, the groundwater tables of four wells from January 1 st 21 to December 31 st 214 were used to validate the calibrated model. The evaluation results and the comparison of observed and simulated groundwater tables of 2 selected wells were shown in Table 3 and Figure 5 respectively. Obviously the simulated data can well fit the observed values. The performance of the model was very good in validation period according to the assessment standard in Table 1. Thus the calibrated model could be used to simulate different water management scenarios QJ CY /1/5 11/1/5 12/1/5 13/1/5 14/1/5 Date (year/month/day) 43. 1/1/5 11/1/5 12/1/5 13/1/5 14/1/5 Date (year/month/day) Figure 5. The comparison of observed and simulated groundwater tables 7

8 Table 3. Evaluation of the simulated results of model validation Statistical parameters Determination coefficient Relative error (%) Nash-Sutcliffe efficiency coefficient table.8 (Good) -.48 (Excellent).71 (Good) 2.3 Model implementation scenarios Scenarios have been developed based on change in water-saving irrigation system, volume of reused water, groundwater use proportion and impact of canal lining. The year of 215 was selected as the initial year. For each scenario, the change of groundwater table and the regional water use efficiency were forecasted using basic data of 59 years. The meteorological data of were used as the basic data. The scenarios considered as follows: (i) Irrigation type: 3 kinds of irrigation type which can be expressed by W1, W2, and W3. W1 and W3 stand for current irrigation practice and controlled irrigation technique respectively. W2 is used to represent the irrigation type of shallow, wet and dry. Irrigation schedules of three irrigation types can be seen in Table 4. Table 4. Irrigation schedules of three irrigation types unit/mm Irrigation schedules Ponding Transplantation and turning green Early tillering stage Late tillering stage Jointing- booting Heading and flowering Milk stage Yellow ripe stage W W W %-5 9%- 5 8%- 1% 9%-3 9%-3 8%- 1% 7%- 1% % represents the percentage of saturation moisture content (ii) (iii) (iv) Volume of water reuse: 3 kinds of water reuse volume can be represented by R1, R2 and R3. They stand for the reuse volume of 5%, 4% and 8% respectively. use proportion in rice growth period: it can be expressed by P1, P2 and P3. They stand for the proportion of 6%, 7% and 1% respectively. Among the three proportions, 1% represents the current situation. Canal section earthen or lined: The letter N and Y can be used for representing whether there is canal lining. In all, 45 scenarios would be obtained. Taking the scenario of NW1R1P1 for example, it stands for no canal lining, current irrigation practice, water reuse volume of 5%, and groundwater use proportion of 6% in rice growth period. 8

9 NW1R1P1 NW1R1P3 NW2R1P2 NW3R1P1 NW3R1P3 YW1R1P2 YW2R1P2 YW3R1P2 NW1R2P2 NW2R2P1 NW2R2P3 NW3R2P2 YW1R2P1 YW2R2P1 YW3R2P1 NW1R3P1 NW1R3P3 NW2R3P2 NW3R3P1 NW3R3P3 YW1R3P2 YW2R3P2 YW3R3P2 table change (m) 2 nd World Irrigation Forum (WIF2) 3. RESULTS AND DISCUSSION 3.1 table analysis The groundwater tables of 45 scenarios were evaluated by the developed semidistributed water balance model. The average groundwater table in the study area is about 13.3 m below the surface nowadays. On this basis, the value of groundwater table change was used when analysing these scenarios. The results of groundwater table change for each scenario are shown in Figure Scenarios Figure 6. The groundwater table change for each scenario According to the current water management strategy, the groundwater table can be declined by m in 59 years with an annual rate of cm. The declining trend can be alleviated by adopting water-saving irrigation techniques, but the effects are not obvious. The groundwater table will be declined by m after using the watersaving irrigation technique of shallow, wet and dry, and it will be declined by 4.13 m with controlled irrigation. Compared with the current irrigation practice, these two water-saving irrigation techniques can reduce the decline of groundwater tables by 5.1 m and 2.75 m respectively. By opting conjunctive use of surface and groundwater, the groundwater table can be recovered with the increase in surface water supply. Under the condition of current irrigation practice, the groundwater table can be increased by 7.1 m in 59 years when groundwater use proportion in rice growth period decreases from 1% to 6%. If this proportion rise up to 7%, the groundwater table is only declined by 1.95 m. By applying canal lining, the groundwater table will be declined because the recharge will be decreased. Under the condition of current irrigation practice, the groundwater table will rise by 1.61 m in 59 years when groundwater use decreases from 1% to 6%. If the proportion rise up to 7%, the groundwater table will be declined by 7.65 m. Compared with not applying canal lining, the groundwater table of these two conditions can be decreased by 5.49 m and 5.7 m respectively. With the increase of water reuse there are no significant changes in groundwater tables. The main reason is that the amount of water stored in drains was not too much, and it only accounted for a very small proportion of t irrigation water sources. 9

10 3.2 Water use efficiency analysis Ratio of total depletion to net surface inflow (Formula 8) is selected as the indicator to evaluate regional water use efficiency. Total depletion in the study area consists of both rice and non-rice evapotranspiration. The amount of surface water flowing into the area comprises precipitation and irrigation, which can be titled gross surface inflow. The net surface inflow equals gross surface inflow minus the reused return flows. ET FRirn I P (8) Where FR irn= the ratio of total depletion to net surface inflow, ET =the total evapotranspiration in the study area, I = the total irrigation water amount, P= the precipitation, andλ = the reused return flows in the area. The water use efficiency of the analysed scenarios varies from.838 to.923. The bigger the value of FR irn, the higher the regional water use efficiency. For the current water management strategy the value offr irnis.897 and this figure would be improved after adopting water-saving irrigation techniques. The water use efficiency can be improved by 2.12% after using the water-saving irrigation technique of shallow, wet and dry and it can be improved by 1.14% with the application of controlled irrigation technique. By adopting conjunctive use of surface and groundwater, the water use efficiency would be reduced with the increasing use of surface water. Under the condition of current irrigation practice, the water use efficiency would be reduced by 6.5% when the use of groundwater proportion in rice growth period reduces to 6% and it would be reduced by 1.5% when the groundwater proportion rises up to 7%. The water use efficiency would be raised by applying canal lining. Under the condition of current irrigation practice, the water use efficiency would be increased by 4.33% compared with no canal lining when groundwater proportion is 6% of total irrigation water. If the proportion rises up to 7%, the efficiency would be raised by.91% compared with no canal lining. 3.3 Irrigation schedules The core goal of the study is to improve the regional water use efficiency and keep sustainable utilization of groundwater when comparing the 45 scenarios. Thus both groundwater table and regional water use efficiency should be taken into account. In the study area, it is supposed that keeping the groundwater table between the layer of the clay loam and loamy sand is effective for sustainable groundwater development. And the higher the regional water use efficiency, the better the scenario. On the basis of the two rules, the groundwater table change and water use efficiency indicator (FR irn) were standardized respectively and they were given equal weight when calculating the weighted average value for selecting the scenario. The results of this value are shown in Figure 7. It can be seen from Figure 7 that the maximum weighted average value comes from the scenario of YW2R3P1. It stands for canal lining, water-saving irrigation technique of shallow, wet and dry, water reuse volume of 8%, and groundwater use proportion of 6% in rice growth period. The groundwater table of this scenario was declined by 2.89 m in 59 years with annual declining rate of 4.9 cm. Regional water use efficiency 1

11 was.915. Then the water use mode under different hydrological years (wet, normal and dry year) could be proposed based on this scenario. These modes showed the using time and the corresponding water quantity of groundwater, surface water and return flow. Irrigation quota and irrigation schedules were shown in Table 5 and Figure 8 respectively. Figure 7. The weighted average values of model implementation scenarios Table 5. Irrigation quota and the corresponding water quantity in different hydrological years Rainfall sequences Irrigation quota (Gross) (m 3 ha -1 ) Water reuse Irrigation water sources (m 3 ha -1 ) Surface water (Gross) Wet year (25%) Normal year (5%) Dry year (75%) Therefore, groundwater is the main source for irrigation and surface water is used as auxiliary source and water reuse would be used as supplement source. Water in drains and river would have the priority to be reused when irrigation is needed. In ponding period, groundwater is the only irrigation source. The drainage after ponding period could be reused for supplement irrigation after transplantation. However, in other irrigation time, there is little water in drains. Thus the water reuse volume is correspondingly very small. In wet year (25%), irrigation frequency is 13 times. In normal year (5%), the irrigation in ponding period is one time more than the wet year. And the total irrigation times are 14. In dry year (75%), the irrigation in ponding period and rice growth period are both two times more than the wet year. Thus the total irrigation times in dry year (75%) are

12 Irrigation Volume (m³/ha) Irrigation Volume (m³/ha) Irrigation Volume (m³/ha) 2 nd World Irrigation Forum (WIF2) Water reuse Surface water Water reuse Surface water Apr 1-May 9-Jun 9-Jul 8-Aug 1-Apr 1-May 9-Jun 9-Jul 8-Aug Date Date (a) Wet year (25%) (b) Normal year (5%) 7 6 Water reuse Surface water Apr 1-May 9-Jun 9-Jul 8-Aug Date (c) Dry year (75%) Figure 8. Irrigation schedules of different hydrological year 4. CONCLUSIONS The semi-distributed water balance model developed in this paper could be used to quantify water cycle factors in hydrological process of the irrigation district. Totally 45 scenarios were derived with the application of the model. The simulation results indicated that the declining trend of groundwater tables can be alleviated by using water-saving irrigation techniques and opting conjunctive use of surface and groundwater. However the groundwater table would be declined by applying canal lining. Water reuse volume had very little influence on groundwater table. From the perspective of regional water use efficiency, it can be improved by adopting watersaving irrigation technique, using canal lining, and increasing water reuse volume. But water use efficiency would be reduced with the increase in surface water supply under the conjunctive use of surface and groundwater. Both groundwater table and water use efficiency should be considered and given equal weight when evaluating the scenarios. The reasonable irrigation schedules under changing of rainfall sequence (wet, normal and dry year) could be proposed based on the selected scenario. For the study area the reasonable irrigation times for paddy rice in wet, normal, and dry year are 13, 14, and 17 respectively. To maintain sustainable water resources development in the area groundwater and surface water should be conjunctively used with groundwater as the main source for irrigation, and surface water as auxiliary source and reused water as supplement source. 12

13 ACKNOWLEDGEMENTS This work was made by the support of Ministry of Water Resources' Special Funds for Scientific Research on Public Interest (Grant No ), Open Research Fund Program of State Key Laboratory of Water Resources and Hydropower Engineering Science (Grant NO. 215NSG1), National Natural Science Foundation of China (Grant No ). The authors are grateful to Qian Jin Farm and JianSanjiang Water Resource Bureau of HeiLongjiang Province for their assistance. REFERENCES Abbott M. B., Bathurst J. C., Cunge J. A., et al An introduction to the european hydrological systemsystemehydrologiqueeuropeen, SHE, 2: Structure of a physically-based distributed modelling system. J.Hydrol. 87, Arnold J. G., Srinivasan R. Muttiah R. S., et al Large Area Hydrologic Modeling and Assessment.Part I. Model development. Journal of the American Water Resources Association, 34 (1), Chowdhury, A., Jha, M.K., Chowdary, V.M., Mal, B.C., 29 Integrated remote sensing and GIS-based approach for assessing groundwater potential in West Medinipur district, West Bengal, India. Int. J. Remote Sens. 3 (1), Chowdary, V.M., Rao, N.H., Sarma, P.B.S., 23 GIS-based decision support system for groundwater assessment in large irrigation project areas. Agric. Water Manage. 62, Hanson R. T., Schmid W., Faunt. C. C. 21 Simulation and Analysis of Conjunctive Use with MODFLOW s Farm Process. GROUND WATER, 48(5), Jia YW, Wang H, Yan DH. 26 Distributed model of hydrological cycle system in Heihe River basin I. Model development and Verification. Journal of Hydraulic Engineering. 37(5), (In Chinese) Nash, J. E. and Sutcliffe, J. V. 197 River flow forecasting through conceptual models, Part I. A discussion of principles. J. of Hydrology, 1(1), Saleh A., Arnold J. G., Gassman P. W., et al. 2 Application of SWAT for the upper north bosque river watershed. Transactions of the ASAE, 43(5), Shi YF, Jiao XY, Luo YF, et al. 213 Synchronous estimation of the crop coefficient for rice and the seepage model parameters for paddy fields. Advances in Science and Technology of Water Resources, 33(4), (In Chinese) Srivastava P.K., Raj Mohan Singh. 216 GIS based integrated modelling framework for agricultural canal system simulation and management in Indo-Gangetic plains of India. Agricultural Water Management, 163, Wang J.P., Cui Y.L Modified SWAT for rice-based irrigation system and its assessment. Transactions of the Chinese Society of Agricultural Engineering, 27(1), (In Chinese) Zhang X.. 25 Simulating Return Flow of Paddy Rice Based on System Dynamics Approach. Ph.D Thesis. Wuhan, China: Wuhan University. (In Chinese) 13