江苏沿海垦区土壤脱盐过程受排水条件影响的模拟研究

Simulating the Rainfall Leaching Effect on Coastal Saline Soil Facilitated with Subsurface Drainage Systems

江苏沿海垦区具有淡水资源短缺而雨水资源丰富的特点,建设人工排水系统可促进天然降雨对农田土壤盐分的淋洗效果,达到不同的脱盐目标。根据江苏省东台市62年的逐日气象资料,在验证排水模型-DRAINMOD模拟结果的基础上,进一步构建盐分动态模型,分析了不同暗管排水条件下土壤盐分变化过程,建立了研究区盐渍土脱盐效果与排水强度之间的关系。结果表明:DRAINMOD模型较好地预测了地下水位动态变化,所建立的盐分模型对土壤盐分预测值与实测值基本一致;土壤脱盐年限(N/a)与暗管埋深(D/m)及间距(S/m)间的关系可表述为N=11.872-7.385D+0.237S;在排水较好(暗管间距为30 m,埋深为1.2 m)的条件下,土壤的脱盐(<1 g/kg)时间约为10 a;提高排水强度(暗管间距为20 m)后,脱盐时间可降低到8 a;而在排水不畅的情况下(暗管间距>100 m),土壤含盐量经过10年仍在重度(4~6 g/kg)范围内。因此,针对不同的脱盐目标,合理设置暗管排水系统,可加速沿海垦区土壤的脱盐过程,为当地农业生产提供可靠的土地资源。

In coastal reclamation area of Jiangsu Province,fresh water resources are scarce and rainfall resources are abundant.The construction of artificial drainage system can promote the leaching effect of natural rainfall on farmland soil salt and achieve different desalting goals.Based on the daily meteorological data of Dongtai in Jiangsu Province for 62 years,a dynamic model of salinity is established based on the simulation result of DRAINMOD.The variation process of salinity in soil under different drain conditions is analyzed,and the relationship between desalination effect and drainage intensity in the study area is established.The results show that the DRAINMOD model predicts the dynamic change of groundwater level well,and the predicted value of soil salinity by the salt model is basically consistent with the measured value.The relationship between soil desalination period(N/a),depth(D/m)and spacing(S/m)of subsurface pipes can be expressed as N=11.872-7.385D+0.237S.Under well-drained conditions,i.e.drain spacing at 30 m and depth at 1.2 m,the predicted soil desalination(salt content lowered to 1 g/kg)time is about 10 years.While drainage intensity is increased by reducing drain spacing to 20 m,the desalination time is reduced to 8 years.Under poor drained conditions(drain spacing is more than 100 m),the predicted soil salinity remains high even after 10 years of drainage leaching.According to different desalination goals,the subsurface drainage system can be designed reasonably to accelerate the desalting process of soil in coastal reclamation areas and provide reliable land resources for the local agricultural development.