绿洲浅层地下水位与水质变化对人为驱动LUCC的响应——以三工河流域为例

Response of the Changes of Shallow Groundwater Level and Quality to LUCC Driven by Artificial Factors—A Case Study in the Sangong River Watershed in Xinjiang

以新疆三工河流域绿洲为例,应用遥感、地理信息系统、空间插值和统计分析的方法,初步分析干旱区绿洲土地利用/土地覆被变化对绿洲浅层地下水位水质变化的影响。研究数据包括1978、1987和1998年三期遥感数据和近25年8口常年观测井水位数据及1987和1998年两期20口观测井水质数据。结果表明,绿洲随着城市、工矿用地为主的非农业用地和以耕地为主的农业用地的持续增加,浅层地下水水位与水质发生了显著性的时空变化。冲洪积扇绿洲主要城镇聚居区地下水位以年均45cm的速率下降,冲积平原下部绿洲地下水位以年均7cm的速率呈现缓慢的上升趋势;绿洲地下水水质趋于恶化,矿化度总体呈现上升的态势,且冲积平原绿洲地下水矿化度上升的幅度普遍大于冲洪积扇绿洲,这与地形、水文地质条件、土地资源开发、灌排强度、地表蒸发、化学肥料和农药的使用密切相关。

Taking an oasis of Sangong River watershed,located on the northern slope of Tianshan Mountains of Xinjiang as a case,we studied the impacts of land use/cover change(LUCC)on shallow groundwater level and quality in the oasis of arid area,by employing the Geographical Information System (GIS),Remote Sensing (RS) and Geostatistics.Land use/cover was classified mainly into 9 types of irrigated lands,cities,towns,thorps and industrial and mining lands,shrubby lands,desert grasslands,saline or alkaline lands,swamps,reservoirs and ponds,which were extracted from aerial images in 1978,Landsat TM image in 1987 and Landsat ETM image in 1998 by visual interpretation,and groundwater data was obtained from 20 monitoring wells spreading over the entire oasis.The result of research showed that the shallow groundwater level and quality reflected remarkable spatio-temporal changes-in alluvial-diluvial fans descended at avg 45cm per annum in past twenty-five years,the whole trend of water table in phreatic overflowing zones went into a rapid descent,especially in the 1990's,the maximal degree of decent reached 10m.The water table of irrigated land in the under part of the alluvial plain ascended at avg 7cm per annum.The groundwater quality of oasis became more and more deteriorative with an increase in mineralization during 1987 to 1998.The isogram of mineralization in oasis transformed from 200～600mg/l in 1987 to 300～1 500mg/l in 1998,and the degree of increase in mineralization reached 100%～200% at the downstream of the oasis.Anion transited from HCO3- to SO42- and CI-,and cation had a transition of Na+,K+,Mg2+ to Ca2+ in groundwater quality in south-north direction.All of these had close relations with exploitation of land resources,irrigation and drainage,surface evaporation and use of chemical fertilization.In a word,the change of land use/cover by human factor played decisive role in spatio-temporal changes in groundwater table and quality of the oasis in arid area.The sustaining increase in non-agriculture lands of cities and thorps and irrigated agriculture lands caused a remarkable descent in water table at upstream of the oasis,and produced a great effect on groundwater quality at the stream down of the oasis.