Study On The Effect Of Changing Environment On Water Cycle Inirrigation Region

Climate change and human activities have an important impact on the northern irrigationwater cycle. Groundwater is an important part of irrigation water cycle, and its water leveldynamic groundwater circulation is the inevitable result of the response to changes in theenvironment.To a certain extent, it reflects the irrigation water cycle is healthy or not, directlyaffects the effective safety utilization of irrigation area water resources. Therefore, studyingon the influence of environmental change on irrigation water cycle for promoting sustainabledevelopment and utilization of water resources in irrigation area has important theoreticalsignificance and application value.The paper selected baojixia irrigation as the research area, using the actual research;statistical analysis and simulation of the water balance calculation method of combining studythe effects of environmental changes on groundwater circulation of irrigation area, and theadaptability of irrigation area water resources sustainable utilization countermeasures arediscussed. Through analysis obtained the following results and conclusions:(1) The paper generalized the irrigation water cycle system, based on analyzing theconversion relationship between the precipitation, surface water and groundwater.The paperthink that drainage Wells combined with irrigation water cycle is mainly embodied in theconversion between surface water and groundwater under certain conditions ofprecipitation.Therefore, researching of groundwater circulation contributes to perceive the lawof irrigation water cycle. On this basis, from the perspective of groundwater system and theexternal environment, to identify the main factors influencing the groundwater circulation areprecipitation, evaporation, feeding water, groundwater exploitation.(2)Analyzing interannual and annual variation characteristics of annual precipitation, evaporation, feeding water,water proportion of drainage well, groundwater exploitationof irrigation area from1981to2010. The results show that: precipitation of irrigation area innearly30years is overall decline and fluctuate, with the characteristics of annual unevendistribution and large interannual changes. Diversion flow at headrace of linjia villageremained stable; Diversion flow at headrace of weijia village increased slowly. Irrigationgroundwater exploitation had a trend of decline; Groundwater exploitation of yuanxia irrigation is greater than the groundwater exploitation of yuanshang irrigation.（3）Based on water balance method, groundwater circulation elements in irrigated areawere analyzed and calculated by different frequency representative years. In normal flowyears (P=50%), the amount of precipitation infiltration recharge, canal seepage recharge,field irrigation infiltration recharge, well irrigation mining regression recharge respectivelyaccounted for46%,35%,16%and3%of total recharge. Dry years (P=75%) accounted for45%、37%、13%、5%.Especially dry years (P=95%) accounted for35%,42%,19%,4%.Theabove data show that, the amount of recharge in normal flow years, dry years and especiallydry years were in turn reduced, respectively were340million m3,280million m3,276millionm3.The amount of excretion were in turn increased, respectively were140million m3,180million m3,240million m3.This reflect that precipitation, surface water irrigation andgroundwater exploitation had an important influence on groundwater circulation in theirrigation area.（4）Based on the groundwater circulation factors analysis in variation environment ofirrigation area, grey model and BP artificial neural network model and the gray neuralnetwork model were established. Using the three kinds of model to simulate and test theburied depth of underground water level in the irrigation area. The calculation accuracyanalysis show that, their average relative error respectively was2.01%,1.54%and0.45%.Therefore, we conclude that based on the gray neural network model to simulate the burieddepth of underground water can be used for simulation study on dynamic effects ofenvironmental changes on irrigated groundwater level.（5）According to the change trend of the change environmental factor in irrigation area,this paper set the climate change situation and human activities change situation. Based onthe gray neural network model,14kinds of buried depth of underground water level in theirrigation area under two situations were simulated and analyzed. The results show that: thegreater the range of precipitation decreases, the greater the buried depth of ground water leveldrops. Namely, the precipitation decrease1%,3%and1%respectively, the range of burieddepth of underground water level in the irrigation area was+0.01m,+0.03m,+0.06mrespectively, while the rate of buried depth of underground water level was0.002%,0.148%,0.267%respectively. This paper had determined the suitable proportion of drainage wellirrigation water in different frequencies in irrigation area, normal flow years (P=50%) wasabout2.9, the dry year (P=75%) was about3.1.