A Study Of Dynamic Analysis And Artifical Recharge Of Groundwater In Irrigation District Combined Of Well And Canal Under The Condition Of Over-exploitation Of Groundwater

As an important component of water resources，groundwater plays an important role inpromoting healthy and harmonious development of society and economy, and maintaining thebalance of ecological environment. However, due to lack of understanding of the supportingrole of groundwater resources in ecology and environment, over-exploitation of groundwaterand many resulting environmental problems are increasing. Therefore, it has an importantsignificance for the sustainable use of water resources and for overall control of "Sanshui" tocarry out research and practice such as dynamic analysis and artificial flood storage under thecondition of over-exploitation of groundwater,.Jinghuiqu, located in the Guanzhong Basin in Shaanxi Province, called Zheng Guoqu inthe past, is one of the three ancient water conservancy projects in China. As a typical well andcanal two-irrigation district, experienced several investments in improvement and expansion,it became a large-scale irrigation district with a combination of canal and well, Irrigation anddrainage with complementary, saline controlling and high yield. It made a great contributionto the security of the regional food production. Its joint use of surface water and groundwateris a good example for the utilization of water resources in China’s large-scale irrigationdistricts.But in recent years, due to the development of socio-economic and local changes innatural conditions, coupled with the reform of the management system and the adjustment ofthe price of water and other reasons, groundwater in Jinghui irrigation district wasover-exploitated in successive years. Especially in the21st century, the imbalance ofgroundwater intensified. Groundwater levels of large areas was declining, the area of the coneof depression was expanding, and the resulting series of environmental and geologicalproblems. Therefore, dynamic analysis of groundwater under the conditions ofover-exploitation, carrying out research of artificial recharge of groundwater, restoration anddevelopment of underground water, further scientific implementation wells combined withcanals, achieving joint use of "Sanshui", all of which become effective ways to solve theproblem.This paper relied on the project of Water Resources Department of ShaanxiProvince,"improve water use efficiency of large-scale irrigation district, and promote theproject of the trial and demonstration of new socialist rural construction", which is undertakenby Water and development Institute of Chang’an University. this paper carried outgroundwater resources assessment of, demonstrated the feasibility study to promote theartificial recharge of groundwater in this area. On the basis of the results of previous studies,taking account of evolution of environment and influence of human activities, thehydrogeological conditions, transformation rule of groundwater system and dynamiccharacteristics under the condition of over-exploitation of groundwater in typical irrigationdistrict combined of well and canal-Jinghuiqu Irrigation District are alalyzed. The paperestablished a three-tier structure, taking account of3D dimension stochastic and deterministicprediction model for groudwater(GSDM). The present situation of groundwater, the dynamicchanges of groundwater without artificial recharge and with2kinds of recharge methodsduring the next20years are caculated, predicted and evaluated through many ways. Couplingwith the test and taking the GSDM model as a platform, promoting artificial recharge of of groundwater in lagre scale in irrigation district was studied. The creative achievements aregained as follows:1,Describe the concept and principles of artificial recharge of groundwater systematically,analyse of the factors affecting artificial groundwater recharge, and sum up the advantagesand disadvantages, and the calculation of the theory used for artificial recharge ofgroundwater was summarized. Having looked to new technologies, new methods and newtheory of the future research and implementation of artificial recharge of groundwater.2, Analyse the hydrogeological environment of groundwater systems of the study areasystematically and the dynamic evolution process of groundwater under the condition ofover-exploitation; based on the "Sanshui conversion" principle to determine the relationshipof water balance and equilibrium parameters for the water balance calculation in the status. Itsuggested that the ground water was in a serious state of negative balance, over-exploitedseriously. It showed that artificial recharge of groundwate in a large area in the irrigationdistrict should be carried out without delay, which also provides study of artificial rechargewith the necessary data support.3, Integrate hydrogeologic conceptual model the the study area and GIS, throughdetermineing the various hydrogeological parameters, boundary conditions, initial conditions,the source terms and the time step, establish stochastic and deterministic coupling predictionmodel under the exploitation conditions of the status quo and forecast calculations for20years, the results show that: the future groundwater irrigation system will be in negativebalance status, the difference will reach-87952×104m3, remains a serious over-exploitation.And the water level continuous falls, the scope of the cone of depression further expands,even formating of some new funnels, which presents a serious challenge for sustainabledevelopment of groundwater in this area.We must now must take the necessary measures toreduce groundwater exploitation to prevent possible environmental geological disasters.4. Analyse the necessity and feasibility that carrying out artificial recharge of groundwaterin this irrigation district. Try to establish an evaluation index system of artificial recharge ofgroundwater in irrigation district, and identify all evaluation factors which are irrigation waterrecharge coefficient, hydraulic conductivity, specific yield, dewatering aquifer thickness,groundwater depth and intensity of mining. Use AHP (Analytic Hierarchy Process) todetermine the weight of each evaluation factor. Finally, the paper made a statistical analysisfor the evaluation index system by using MapGIS, and divided the suitable groundwaterrecharge district according to the analysis.5, In order to study the mechanism that agricultural irrigation water supplies groundwater,calculating recharge and recharge efficiency and other parameters, and in order to evaluate thebest way to cited infiltration recharge and provide policy and advice for irrigation district tocarry out large-scale artificial recharge of groundwater, this study carried out a test ofartificial recharge to fan out from point to area, the results showed that: artificial recharge testcan make local groundwater table rise, and this phenomenon can quickly extend in a largearea to the external test site, indicating that the effect of recharge in the irrigation district ismore obvious. The artificial recharge of groundwater and recharge factors of this area werecalculated too.6. Combined with the test, this paper proposed two preliminary groundwater rechargeprogram, to predict the restoration effect for20years under each artificial recharge program and make a comparative analysis of various options by using GSDM. The results showed thatboth of the two recharge programs can make the district’s water table be restored to a largeextent, and the second recharge programe was more effective than the first one. Furthermore,according to the results of water balance calculations, the paper estimated the time that thewater table level of this irrigation district could come back to the one in the target year(1979)required about24years.