内蒙古黄土高原区降水规律与集雨利用潜力分析

在黄土高原干旱少雨,地下水埋深较深的地区,通过建立水窖集雨供人畜饮用和作物补充灌溉具有重要意义。本研究利用沙圪堵镇的准格尔旗气象站1959—2000年气象资料,进行降水规律分析。结果表明,位于内蒙古黄土高原区的准格尔旗年均降水量为392.1mm,最大年降水量为635.5mm,最小降水量仅为142.5mm。年降水量在500mm以上的保证率为19%,接近五年一遇,年降水量400mm以上的保证率为44%,可基本上满足短季耐旱作物的生长之需;降水量在300mm之下的频率为21%,不能满足作物生长对水分的需求。有1/3的年份年降水量300—400mm之间,作物生长所需水分亏缺的部分,需要适当补灌。由于4—5月作物播种和苗期降水量少,存在生长障碍,如能在前一年集雨次年春天补充灌溉将有利于全苗和增产。对于10mm以上的降水,保证率80%以上的降水量仅为135mm,保证率60%的降水量为200mm。中雨雨量为达到300mm的保证率只有30%。对于大雨过程,总降水量200mm只有15%的可能性,100mm以上的保证率为60%。如果降水10mm以上才能集到雨水,100m2的集雨面,只有60%的年份产水量大于20方。不同集雨面的集流效益不同,在建立集雨水窖时,要根据水窖体积和集雨面材料的集流效率,合理确定集雨面,保证80%以上的年份达到满意的集雨效果。另外,根据降水规律可利用自然地面进行田间集雨,利用土壤库容保存降水供作物生产之用。

Analysis on the Rainfall Regular and Potential of Collecting and Utilizing Rain in Loess Plateau of Inner Mongolia

The precipitation is fewer in drought region.Water vault is built to collect rainfall for supplying human and domestic animal and using water for the crop complementary irrigation in the region of low ground water level in loessial plateau.The data of Zhunger weather station from 1959 to 2000 was used to analyse the precipitation rules.The Zhunger county locates in region of loessial plateau in Inner Mongolia and its land area is 7535 km3.The annual precipitation is 392.1mm,the region may yield 29.50×108m3water from rainfall.Among this rainwater,the water is about 24×108m3from the daily rainfall higher than 5mm,184×108m3from the daily rainfall higher than 10mm,9×108m3from the daily rainfall higher than 25mm,3×108m3from the daily rainfall higher than 50mm.The precipitation variation is great(29%).The most precipitation was 635.5mm(1961)and the least was 142.5mm(1965).The probabilities of annual precipitation are 19%,44%,21%,correspond to rainfall over 500mm,400mm and 300mm.The probabilities is lower when annual rainfall is below 250mm.The precipitation of daily rainfall more than 10mm is 135mm when the probability higher than 80%,and is 200mm when the probability higher than 60%.If the annual precipitation of daily rainfall more than 25mm is 300mm,the probability is about 30%.To the rain of daily rainfall more than 25mm,if total rainfall is 200mm,the probability is about 15%;if total rainfall is 100mm,the probability is about 60%.If the water vault could collect efficaciously rainwater when daily rainfall is more than 10mm,its probability is about 60% that 100 m3surface of collecting rainfall could collect rainwater more than 20m3.The efficient ratio of collecting rainwater is different on different surface.When a water vault is upbuilt,the surface area of collecting rainwater is to be made sure according to water vault volume and surface material of collecting rainfall.Other side,the rainwater could be collected from natural ground surface to the field.The soil could save the water and use it for crop growth.