东北西部沙地近20年地下水变化动态及其成因分析

The Changing Dynamics of Groundwater and Its Relationship with the Precipitation and Desertification in the Western Part of Northeast China since Recent 20 Years

本文以奈曼旗为例 ,分析研究了我国东北西部沙地 1979- 1997年地下水位时空变化规律及其与降水量和沙漠化的关系。结果表明 :(1)沙地多年平均地下水位为 2 .19m ,其中农区为 2 .85m ,牧区 1.16m ;(2 )地下水位是1981- 1983年最低为 2 .4 9- 2 .5 6m ,1991- 1992年最高为 1.90 - 1.92m ,1997年为 2 .2 2m ,高于 1979年的 2 .4 1m ;(3)该区季节最高水位主要发生于春季 (3- 5月 ) ,发生频率占 5 0 .1% ,最低水位主要发生于冬季 (12 - 2月 ) ,发生频率为 4 1.2 % ,平均 4月最高为 2 .0 7m ,10月最低为 2 .2 3m ;(4)地下水位的年际变化动态和降水量密切相关 ,但有滞后 1- 2年的现象 ;(5 )地下水位空间分布上的差异与土地沙漠化及土地利用方式密切相关 ,沙漠化土地主要用于放牧 ,由于人为利用少和蒸散少 ,有利于地下水抬升 ;(6 )由于耕地面积占总土地面积比例低 ,水浇地和粮食产量的增加尚未对地下水位造成严重影响。

By taking Naiman Banner located in the eastern part of Inner Mongolia as a case study, this paper analyzes and researches the temporal and spatial change of groundwater level and its relationship with the precipitation and desertification over the sand lands in the eastern part of northeast China since recent 20 years. The results are as follows: (1) The multi-year average groundwater level over the sand lands is 2.19 m, in which it is 2.85 m over the rural areas and 1.16 m over the pastoral areas. (2) The lowest groundwater level, 2.49-2.56 m, occurred during 1981-1983, the highest one, 1.90-1.92 m, occurred during 1991-1992, and the groundwater level was 2.22 m in 1997 and higher than that of 2.41 m in 1979. (3) In the region the highest seasonal groundwater level occurs mainly in spring (March to May), its occurring frequency occupies 50.1%, and the lowest one mainly in winter (December to next February), its occurring frequency is 41.2%. In average the groundwater level is highest (2.07 m) in April and lowest (2.23 m) in October. (4) The interannual changing dynamics of the groundwater level is closely related to the precipitation, it, however, delays for 1-2 years. (5) The difference of the spatial distribution of the groundwater level is closely related to the land desertification, the desertificed lands are mainly used for grazing, which is advantageous for raising the groundwater level because of the less use and less evaporation of the groundwater. (6) As the proportion of the farmland area is low in the total land area in the region, the increase of the area of irrigated land and of grain yield does not result in a serious impact to the groundwater level yet.