Study On Management Strategy Of Irrigation District Based On Groundwater Depth And Exploitation

Groundwater is not only an important part of water resources system, but also the primary water supply source of many large irrigation districts in north China, which has a critical role in social-economic development and ecological environment maintenance. In recent years, influenced by factors of climate change and human activities, demand-supply conflict in northern irrigation is becoming more and more obvious, and agricultural irrigation activities are relying heavily on groundwater. The exploitation-replenishment imbalance of groundwater lead to a series of problems of ecological and geological environment problems, which caused a direct impact on irrigation water resources safety efficient utilization and sustainable development.In this paper, on the basis of summarizing the predecessors’ research work, selected Jinghui Canal irrigation district in Shannxi province as the research object, using qualitative analysis combined with quantitative research, to explore the management strategy of irrigation district based on groundwater depth and exploitation. The conclusion is mainly:(1) From the perspectives of the composition, function and structure, generalized the irrigation groundwater system, and analyzes the correlation between each function of groundwater system; through the analysis of groundwater regime and recursive elements, it is considered that under the dual effects of natural and artificial factors, groundwater recharge of rainfall infiltration and canal system remains decreasing, while artificial exploitation of groundwater discharge keeps increasing, annual variation characteristics of groundwater turned into the type “decreasing by stage” from “unimodal valley” type and “double-humped” type; analyzed by principal component method, natural driving factors and main artifical controlling factors are determined.(2) Based on water balance principle, analyzed the connection between system equilibrium and groundwater level, and the connection between artificial exploitation and groundwater level; according to the dynamic and static combining method, expounded the suitable, prewarning and critical groundwater state, goals of groundwater management in irrigation district were discussed; the index system of groundwater management consist of overdraft evaluation and supervision assessment system was proposed, and the process of groundwater management was cleared.(3) With the hydrologic geology partition as the calculating unit, equilibrium model of groundwater was established according to the irrigation data for groundwater-overdraft evaluation. The result shows that, the irrigation district is in the state of groundwater over-exploited for many years, the annual average ultra picks quantity is 17.5991 million cubic meters per year; coefficient of exploitation is determined as 1.10. Among all the partitions, IB, IIB and IV are determined as potentiality, equilibrium and severe overdraft area, respectively, IA、IIA、IIC and IIIB are determined as general overdraft area.(4) According to the connotation of suitable groundwater depth, using the qualitative analysis combining with dynamic data correlation method, the minimum threshold, prewarning value and maximum threshold of suitable groundwater depth are determined as 2.51 m, 6.54 m and 17.83 m, respectively; the variation of suitable groundwater depth is similar with phreatic water depth and water- abundance of strata, as in gradually decreasing trend from north to south, and in high groundwater level in central area of irrigation district.(5) In order to make the groundwater depth rise to suitable groundwater depth in next decade years, annual average groundwater depth management range indicator is determined acroding to thresholds of suitable groundwater depth, using Controlled Auto-Regressive model as technical means, water supply ability and the water-saving level of the base year(2010) is considered, management plan under different precipitation scenarios are proposed through the test algorithm; according to current situation, the management strategy and safeguard measures such as policy, economy and technology were discussed in this paper.