| Well-canal combined irrigated mode can improve the effective utilization rate of irrigation water, also can prevent soil salinization by adjusting underground water level,which is the development direction of irrigation district in the north of China. Due to lack of joint utilization of surface water and groundwater resources unified planning, irrigation district has a series of ecological environment deterioration problems, such as groundwater over-exploitation, imbalance of exploitation and supplement of water resources, which restricted the sustainable development of the irrigation area. Therefore, improve the effective utilization of water resources and control the underground water level, ensure reasonable use of surface water groundwater, promote sustainable development of the irrigation district is of need and urgency. Well-canal combined irrigation district is a complex of hydrological system, on the one hand, the water resources allocation is restrained by the groundwater, on the other hand, the spatial-temporal pattern of water resources influence the spatialtemporal of drainage, which make the change of groundwater. It is difficult to reflect the groundwater drainage and the change of spatial distribution by using exploitable groundwater resource as a constraint in the optimal allocation of water resource. Groundwater numerical simulation and optimum coupling will be the development direction of well-canal combined irrigation district.In this paper, jinghui irrigation district was chose as a research area. Considering the actual situation, irrigation water requirement of main crops were calculated by using FAO Penman-Monteith equation and crop coefficient method. The changes of irrigation water requirement to the variation of climate and crop planting structure were analyzed. Water demand were calculated by using quota method, water supply and demand balance was analyzed. The coupling system of temporal and spatial optimization of water resources and groundwater numerical simulation model was established.The main research contents and results are as follows:( 1) Irrigation water requirement of main crops were calculated, the changes of irrigation water requirement to the variation of climate and crop planting structure wereanalyzed. The results show that rainfall has a decreasing trend and ET0 has a increasing trend under climate changes,which resulted increasing in the main crop irrigation quota. With the reduce in planting areas of the grain crops and cotton, and increase in planting area of the other economic crop,The net irrigation water requirement shows a trend of decrease. The net irrigation water requirement increases minor under the decreasing in total irrigation area,planting structure adjustment and climate changes.(2)Water demand of agriculture、industry and domestic were caculated by using quota method, also water supply and demand balance was analyzed, then the water demand was obtained in different hydrological years. According to the scale of water storage project, water diversion capacity and limiting conditions, surface water supply amount was calculated in different hydrological years. According to the existing literature, the preliminary exploitation of groundwater was obtained, water supply and demand balance was analyzed. The total water demand quantity in wet year, median year and dry year is 426.66 million m3、502.73 million m3、661.9 million m3 in 2010, respectively; the total water demand quantity in wet year, median year and dry year is 420.03 million m3 、478.33 million m3、626.37 million m3 in2020, respectively; the total water demand quantity in wet year, median year and dry year is417.72 million m3 、473.87 million m3、614.81 million m3 in 2030, respectively. In wet year(25%) and median year irrigation district is not water shortage, in dry year(75%)irrigation district is water shortage, water deficit in 2010、2020 and 2030 is 51.06 million m3、35.89 million m3、21.51 million m3, respectively.(3)According to the actual situation of Jinghui irrigation district, based on the balance of supply and demand of water resources, spatiotemporal optimization model of irrigation water was established. AFSA( artificial fish swarm algorithm) and PSO( particle swarm optimization) was used to allocate water resources. The optimization allocation provide a basis for the study of groundwater simulation.(4)Irrigation district hydrogeology conceptual model and mathematical model was established, Visual MODFLOW was used to simulate and verify the groundwater. Results showed that the model of the observation well fitting was well, the actual condition of underground water was described well, and it can be used for simulating the dynamic change of underground water.( 5) Using surface water diversion and groundwater extraction volume as coupled variables, optimal allocation model system for water resources coupled groundwater simulation model is developed. Optimal results in Jinghuiqu irrigation district showed that water demand can be met in wet year and median year. Water shortage in dry year in 2020 and2030 were 44.89 million m3 and 39.01 million m3, respectively, mainly in March, June 、Julyand Augst, which the period of high water demand and sandiness. In 2020, surface water exploitation quantity in wet year, median year and dry year were 305.64 million m3、337.59 million m3、406.48 million m3, respectively; groundwater exploitation quantity in wet year,median year and dry year were 114.39 million m3, 140.74 million m3 and 175.0 million m3,respectively. The average variations of groundwater level were 0.48 m, 0.06 m,-0.45 m,respectively. In 2030, surface water exploitation quantity in wet year, median year and dry year were 293.15 million m3、 329.67 million m3、 414.3 million m3, respectively;groundwater exploitation quantity in wet year, median year and dry year were 124.57 million m3, 144.2 million m3 and 161.0 million m3, respectively. The average variations of groundwater level were 0.23 m,-0.03 m,-0.26 m, respectively. Balance between groundwater recharge and discharge basically realized. Groundwater levels declined slightly. The model system of optimal model coupling groundwater simulation model can make full use of surface water and groundwater, and control the decline trend in the groundwater level. It is an effective way to achieve rational use of water resources and ecological health in canal-well irrigation district. |
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