利用地下水模型模拟分析灌区适宜井渠灌水比例

为了获取泾惠渠灌区适宜井渠灌水比例,科学合理地确定农业节水方案,该文综合应用ArcGIS和PMWIN地下水模拟软件建立了灌区的地下水分布模拟模型,根据灌区历年农业用水实际情况设定了10种灌溉情景模拟灌区地下水位的变化趋势,通过地下水模型分析研究了灌区井渠灌水比例。利用VB程序语言改写EVT蒸发蒸腾子程序包,使其能模拟非线性蒸发,潜水蒸发量计算精度得到较大改进。研究表明:1)渠首有效灌溉引水量在3.7～4.1亿m3,井渠灌水比例控制在0.35～0.55,基本可以保持灌区地下水采补平衡;2)渠首有效灌溉引水量在1.5～2.0亿m3,井渠灌水比例控制在0.5～0.7,也能实现灌区地下水采补平衡;3)目前井渠灌水比例在0.9～1.2,已引起灌区地下水超采。建议井渠灌水比例控制在0.5～0.7,加大农业节水力度、增加水价财政补贴、进行地下水人工调蓄,实现灌区水资源高效持续利用。

Analysis of suitable irrigation water ratio of well to channel based ongroundwater model

In order to obtain the suitable irrigation water ratio of well and channel to determine scientific and reasonable agricultural water saving scheme in the Jinghui Canal Irrigation District, the ArcGIS and PMWIN software were integrated together to establish the groundwater distribution simulation model of the irrigation area. The EVT evapotranspiration subroutine of PMWIN was rewritten with the VB programming language so that it can simulate the nonlinear evaporation. The simulation accuracy of evaporation was greatly improved. According to the actual situation of agricultural irrigation, 10 kinds of water-saving irrigation simulation scenarios were set up to simulate the change of groundwater depth. Then the suitable irrigation water ratio of well to channel was obtained through the groundwater equilibrium analysis. The results show that: 1) It can keep a balance between groundwater supply and drainage when the irrigation water ratio of well to channel is at 0.35-0.55 with irrigation intake water amount of 0.37-0.41 billion m3 from canal head; 2) It is possible to keep a balance between groundwater supply and drainage when the irrigation water ratio of well to channel is at 0.5-0.7 with irrigation intake water amount of 0.15-0.2 billion m3 from canal head; 3) The current well and canal irrigation ratio of 0.9-1.2 has led to excessive extraction of groundwater. It is recommended that the ratio of well to canal irrigation should be controlled at 0.5-0.7 through agricultural water-saving efforts, increasing financial subsidies to water price and artificial regulation of groundwater storage, so as to achieve the efficient and sustainable use of water resources in the irrigation district.