Study On Adjusting And Controling Patterns Of Wells Connecting With Canals Based On The High-efficienty And Safety Of Water-using In Irrigation Area

As a basic natural resource, water is essential for human survival. Besides, as a strategiceconomic resource, water is the lifeblood which promotes the national economy developmentof all water use sectors. In the northern irrigated area, water resource plays an indispensablerole. As the ancient poetry says:“the river surrounds the green farm land”, which shows theimportance of water for irrigation area. Wells connecting with canals is an important way innorthern irrigated areas. Making the effective connecting with canals and regulatingunderground water reasonably, to realize the effective and safe utilization of water resourcesin irrigated areas, which becomes a practical and hot t issue in the research field ofagricultural water resources. Hence, the research on the wells connecting with canals modelbased on the efficiency and safety of water resources utilization is very important to thesustainable development of irrigated agriculture.Taking Baojixia irrigation district of Shaanxi province as the study area, on the basis ofanalysis about the present situation of irrigation water resources utilization, the reasonableinterval of underground water level’s change was studied. Then, based on the software GMS,the numerical simulations of short-term and long-term underground water level in theirrigation district was conducted to research the groundwater exploitation scheme Finally, theengineering layout and management strategies were discussed. The main conclusions are asfollows:(1) The concepts, principles and research methods of controlling key groundwater levelin irrigation districts were illustrated in this paper. Besides, based on the calculation of rainfallfrequency,different hydrological typical frequency years were determined. Furthermore, basedon the groundwater balance calculation, the reasonable interval of ground water depth rangein irrigation district was preliminarily determined. More specially, on the tableland irrigationdistrict, the largest water buried depth was84m, the smallest water buried depth was5m;whereas under the tableland irrigation district, the largest water buried depth was40m, thesmallest water buried depth was5m.(2) Based on the analysis of aquifer characteristics and hydraulic characteristics inirrigation district, the corresponding mathematical model was established throughgeneralizing groundwater flow of irrigation district as plane two-dimensional unsteady flow.Besides, solving, identification and verification for the above model was done by usingMODFLOW module in the software GMS9.2.6, which indicated that calculated water levelfitted well with the measured data. Calculated flow field basically reflected the trend andpattern of groundwater flow. In this case, it could be thought that the established mathematicalmodel could be used for simulation and prediction of underground water level in the irrigation district.(3) According to the rainfall variation trend and current situations of wells connectingwith canals, two kinds of scenarios of rainfall decline and groundwater exploitation increasewere made. Using the existing groundwater numerical simulation model, the short-term andlong-term groundwater level in the irrigation district were simulated and forecasted. Resultsshowed that in the circumstance of rainfall decline, the burial depth of the underground waterlevel could be controlled within the scope of critical groundwater level if maintaining thegroundwater exploitation intensity in the status quo year. In the circumstance of groundwaterexploitation increase,the burial depth of t groundwater level increased continuously, whichbrought about the result that burial depth of the groundwater level in long-term predictionexceeded the scope of controlling critical groundwater level of the irrigation district inlong-term forecast. Through a comparative analysis, it could be concluded that the wellsconnecting with canals scheme in the first circumstance was more reasonable.(4)Lastly, the engineering layout of wells connecting with canals in the irrigation districtwas briefly discussed. Aiming at the existing problems of wells connecting with canalsmanagement in irrigation district, such as well irrigation lack of oversight, the unreasonablewater price formulation and aging and disrepair issues of partial canal systems, plenty ofmanagement strategies were proposed from the following four aspects: improving themanagement policies and regulations, unifying the water price, enhancing the supervision andstrengthening the construction of wells connecting with canals.