双重排水条件下控制措施对银南灌区水稻田水盐关系的影响分析

针对宁夏银南灌区目前存在的排水过量问题,研究者提出了利用控制排水措施,在适当时段减少排水量的建议。然而,灌区在农沟以及更深层的支、干沟及黄河(低地)的影响下,受着深层排水和浅层排水的双重作用。其中深层排水一般不会受到田间措施的影响,它的存在“淡化或中和”了由于浅层排水的减少引起的田间含盐量的增加。本文在对双重排水情况下的水盐运动进行概化的基础上,建立了基于特定地区排水特性的“浅层排水与深层排水比-浅层排水控制率-排水含盐量增加率”的关系。最后结合根据地下水洗淋的临界情况,确定了达到这一目标控制指标以及浅层地下水控制率。结果显示,对于研究的典型情况,当地下水的盐分含量达到临界的1.62 g/l时,可以将1m深的农沟控制至30cm深;这时的浅层地下水仅为现状的14%,即从731mm减少到了102mm。

Water and Salt Dynamics in Rice Fields Under Dual-drainage in Yinnan Irrigation District, China

The YinNan Irrigation District is under the influence of dual-drainage.The deep "intrinsic" drainage usually is be affected by field management practices,and it can potentially decrease the salinity caused by shallow drainage.In this paper,based on a conceptual model of dual-drainage,a "shallow/deep drainage ratio-shallow drainage reduction ratio-salinity increase" relationship was established and the shallow drainage reduction was detormined by controlling depth of field ditch.Finally,using the threshold salinity level as the leaching requirement,it was found that the control depth should be 30 cm,and required shallow drainage depth was merely 14% of the current value,i.e.,and can be reduced from 731 mm to 104 mm.