Rational Allocation Of Surface Water And Groundwater In Irrigation District Based On GWM

Irrigation district,the major production area of agricultural products,is essential to the agriculture.Water shortages is the common problem in irrigation district,and unreasonable water usage also leads to a series of environmental issues,so the rational allocation of water resource in the irrigation district is significant.By allocating surface water and groundwater reasonably and determining appropriate canal-well water ratio,the groundwater level can be kept in a reasonable range and in dynamic balance in canal-well combined irrigation district.This thesis regards the Jinghuiqu irrigation district as research area,and sets up a numerical simulation model of the phreatic water flow via generalizing the local water cycle.What's more,it tries to apply the Ground-Water Management Process—GWM in the district,and seek to find the maximum pumping water under the water level and water yield constraints.After that,the surface water and groundwater is allocated properly with suitable canal-well water use ratio,and with the purpose of providing scientific basis for sustainable use of water resources in irrigation district.The main conclusions of the study are as follows:(1)The water cycle in irrigation district has the natural-artificial characters,and is affected by natural and social factors.The variation of groundwater level in a year and over years can be decided by precipitation and irrigation,and has different states during different periods.Generally the groundwater will be obviously recharged in winter and spring irrigation season,while it will suffer the greatest drain in summer irrigation season.There are three kinds of variation in a year,namely being increase,stabilize or decline.Since 2000 the variation of groundwater level over years tend to be downwards or fluctuated change.(2)Based on the analysis of groundwater cycle in Jinghuiqu irrigation district,the flow is generalized as two-dimensional non-steady flow,then flow model is built by the MODFLOW module of the GMS.Then the model is discerned and verified,and the findings showed thatthe simulation model can properly reflect the distribution of the actual flow field,and water level simulation fits the measured result very well,so the model is thought effective.(3)The files,construction and solution method of GWM,the Ground-Water Management process,has the fixed format,and GWM can be used in groundwater management with single objective.Considering the situation of Jinghuiqu irrigation district,a water resource optimization management model of GWM is developed,whose objective function is maximum pump water,and the constraint is variable values,water level,and pumping water.(4)Based on GWM,when the constraint is satisfied,the largest pumping water for irrigation in normal year,wet year and dry year are 127 million m3,115 million m3 and 139 million m3.Calculation showed during winter,spring and summer irrigation seasons in the irrigation area,the appropriate canal-well water ratio are 2.3?1.9?0.65 in normal year,and 2.4?1.8?0.8 in wet year and 1.9?1.8?0.5 in dry year,when with the largest pumping water for irrigation.(5)The simulation results of the allocation showed that pumping and channeling water for irrigation could be adjusted rationally in different partitions and periods to slow down the falling rates of water level in the decline areas,which wouldn't have bad effects on level fluctuation areas.After adjustment according to the allocation scheme,groundwater current doesn't change basically,while the water level as a whole rises by one meter,and several regional cones of depression become narrow at the same time.