河西走廊昌马灌区土壤水盐动态特征及脱盐规律

昌马灌区处于西北内陆典型的干旱区,由于自然环境差,蒸发作用强烈,平原区土壤含盐量较高.拟建的"疏勒河农业灌溉工程"实施区80.9%的开垦土地为盐渍土,盐渍土改良方式以及现状水盐平衡的变化对环境特别是下游溶泄区的影响引起了各界的关注.在分析土壤盐份动态影响因素基础上,根据昌马灌区水土盐动态观测资料,将土壤盐分动态分为6种类型.同时发现难溶盐CaCO 3的稳定带不在中游,而在下游安西-敦煌盆地和花海盆地,从而为土壤可溶盐含量计算和排盐设计找到了理论依据.通过对比典型原位淋滤试验,获得了洗盐效果与淋洗方式的关系,建立了试验中原盐剩余率与累计入田间淋洗水量的相关关系,为工程设计和政府决策提供了依据.

WATER AND SALT REGIME BEHAVIOR AND PROCESS OF SALT EXCLUSION IN AERATION ZONE IN CHANGMA IRRIGATION REGION, HEXI CORRIDOR

Located in the typital inland arid area of north\|west China, there is a poor natural environment in Changma irrigation region. There is higher salt percent proportion in plain region for phreatic water evaporation. About 80.9% of reclaimed land is salinized soil in Sulehe irrigation developing region, therefore the methods for improving salinized land and the influence on environment, especially in discharge area, caused by the change of water\|salt balance attract much attention of all society. Based on the data of water\|salt behavior in soil, six salt dynamic types can be classified in soil: Salt Discharge, Salt Discharge In Irrigation Period, Salt Charge In Irrigation Period, Stable Type, Salt Dissolved In Irrigation Period, Salt Charge In Rain Period. The steady region of bad\|soluble salt is in the lower reaches of Sulehe river, Anxi\|Dunhuang basin and Huahai basin, instead of the middle reaches of the river. Therefore the content of CaCO\-3 must be calculated when considering the total soluble saline and salt discharge design. By comparing three typical site leaching experiments of dissolvable salt in soil, the solution is that the effect wouldn't distinct if the total salinity were down to 1%~1.5%(mean salt content in 0~100 cm soil profile). For different leaching types, deep drainage system is the most efficient, and the effect is better for larger interval space of canals than another for sallow drainage system. All the conclusion can be the direct basis of project design and drainage administration for local government. Above all, a relation formula is produced between the rate of residual salt and quantity of accumulated leaking water, the decision\|maker can worked out wanted water quantity according to primary salt content, so the scale of soil improvement can be confirmed matching the runoff of a river, in order to fulfill rational usages for water and land in primeval period of drainage basin development.