渭-库绿洲地下水对土壤盐渍化和其逆向演替过程的影响

基于遥感数据,结合地下水位观测资料,本文对渭-库绿洲土壤盐渍化与地下水的关系进行了定量研究,并探讨土壤盐渍化的逆向演替过程。研究表明:渭-库绿洲在地下水埋深2.3~2.7 m区间,盐渍地面积占的比例较高,在地下水埋深2.7~3.4 m区间,盐渍地面积占的比例相对较低;渭-库绿洲部分地方地下水位已低于影响地表盐渍化的水位临界值(4.66 m),地下水矿化度低于3 g/L,研究区整体处于有利于土壤盐渍化逆向演替的环境之中;土壤盐渍化的逆向演替过程具有时空特征,由绿洲上部向下部,内部向外部逐步发生逆向演替。

Influence of Groundwater on Soil Salinization and Its Reversal Evolvement in Wei-ku Oasis

Based on remote sensing data,and combined with groundwater level observation data,the study do an quantitative research for the relationship between soil salinization and groundwater,and explore the salinization reversal evolvement of Wei-ku oasis.The results show that: 1) the annual ground water lowered 0.05 meters in the study area,with a downward trend from 1997 to 2001 year;there was obviously declined in ground water from 2002 to 2007 year,the rate was 0.175 meters every year,which was mainly caused by human activity,human land cultivation,a lot of drilling and utilization of groundwater resources,and the rise and fall of groundwater caused soil salinization.2) the middle-mild saline land has declined by 63.1 km2 from 1989 to 2001 year;while the severe saline land has increased by 342.47 km2;the total area of salt-affected land increased 279.37 km2,the average annual increase of 23.28 km2.From 2001 to 2007 year,the middle-mild saline land has decreased by 155.42 km2;the severe saline land area has increased by 70.80 km2;the total saline area was obviously decreased by 84.62 km2,at an average annual decrease rate of 14.1 km2.3) the proportion of salinized land area is relatively high when the ground water level is in the range from 2.3 to 2.7 meters,there was a biggish value in 2.4 to 2.5 meters;the proportion is relatively low when the ground water level is in the range from 2.7 to 3.4 meters;4) Some parts of Wei-ku oasis has already in a reversal evolvement circumstance which is valuable for soil salinization,the ground water table is below threshold(4.66 meters),which would affect the surface salt accumulation,the groundwater mineralization degree is lower than 3 g/L;5) Salinization reversal evolvement presents temporal and spatial characters,and gradually occurs from the upper to the lower,and from the inside to the outside of Oasis.