基于遥感数据分析干旱区人工绿洲灌区的水盐时空分异特征

Spatial-temporal distribution of water and salt in artificial oasis irrigation area in arid area based on remote sensing analysis

干旱区人工绿洲的土壤盐渍化产生和演化过程是一个多要素参与、多层次驱动、多过程耦合的复杂过程。为揭示干旱扬水灌区区域尺度的水盐时空分异特征,以地处腾格里沙漠边缘的甘肃省景泰川电力提灌工程一期灌区为研究区,选取1994、2001、2008、2015年的直接参与驱动区域土壤水盐分异过程的地表盐分、土壤含盐量、地下水矿化度、地表灌水量、地下水埋深等5个指标因子。运用可拓层次分析法确定各指标因子权重,借助ArcGIS软件中监督分类以及空间分析技术,获取各指标因子的空间分布栅格图件,将各栅格图件进行标准化处理后按照指标权重进行空间嵌套并叠加,定量化地分析了研究区区域尺度的水盐时空分异特征。结果表明:研究区次生盐碱地主要分布在东部的封闭型水文地质单元,总体看,研究区内轻度盐碱地面积最大,中度盐碱地次之,重度盐碱地面积最小;从解译的进程发展态势可知,研究区盐碱地还处于发展过程中,并呈现出加速增长趋势;由可拓层次分析法分析各指标因子权重排序为地下水埋深(0.3190)>地下水矿化度(0.2710)>土壤含盐量>地表盐分>地表灌水量,可见,区域内的地下水埋深和地下水矿化度是影响区域尺度水盐时空分异进程的主要驱动因素;研究区水盐时空分布态势与总体地势相关,呈现出西低东高的总体分布特征,由西南向东北以弧线状递增的发展趋势,灌区内东北部封闭型水文地质单元地下水位抬升明显,土壤盐渍化发展迅速。

The process of soil salinization in the artificial oasis in the arid area is a complex process involving multiple factors,multi-level driving and multi-process coupling.To reveal the spatial-temporal distribution of water and salt in arid pumping-irrigation areas,the first phase irrigation area of Jingtaichuan Electrical Pumping Irrigation District in Gansu Province,located at the edge of Tengger desert,was selected as the typical research area.A total of five indicators including surface salt,soil salinity,groundwater salinity,surface irrigation water,and groundwater depth were selected in 1994,2001,2008,and 2015.We determined the weights of each indicator factor by extension analytic hierarchy process.With the help of monitoring classification and spatial analysis technology in ArcGIS software,spatial distribution raster maps of each indicator factor were obtained,and each raster map is standardized,the space is nested and superimposed according to the weight of each index factor,so as to get the spatial-temporal distribution of water and salt in the regional scale.The results showed that:1)The weight of each factor affecting the spatial-temporal differentiation process of water and salt on a regional scale was ranked as follows:groundwater depth(0.3190), >groundwater salinity(0.2710), >soil salinity(0.1971), >surface salinity(0.1748),and >surface irrigation(0.0381).Groundwater depth and groundwater salinity were the main driving factors affecting the spatial-temporal differentiation of water and salt at regional scales.2)The saline land in the study area were mainly distributed in the eastern closed hydro-geological units.Overall,the area of mild saline land was the largest,accounting for 7.22%-11.12%,followed by moderate saline land,accounting for 3.19%-5.72%,the area of heavy saline land was the smallest,accounting for 3.03%-4.91%during 1994-2015.The saline land in the study area was still in the process of development,and showed an accelerating growth trend.Among them,the development speed was mild saline land area >the moderate saline land >the heavy saline land.3)The spatial and temporal distribution of water and salt in the study area was related to the overall topography.The distribution of total equivalent value of water and salt was low in the west and high in the east,increasing from southwest to northeast in arc diffusion development trend,affected by natural geomorphology and topographic conditions.With the passage of time,the total can be divided into two stages:stable development period(1994-2008)and rapid development period(2008-2015).Affected by the continuous expansion of the regions with higher total water and salt content in the east to the west,the security of cultivated land resources in the west was potentially threatened,and the overall development trend of water and salt in the study area was not conducive to the sustainable development of agricultural production in the irrigated areas.Based on the analysis of single driving factors,this study proposes an important means for coupling and superimposing multiple driving factors,which provides a new visualization for the comprehensive development of the spatial-temporal differentiation of water and salt in the study area.It can provide useful reference for studying the development trend of spatial-temporal differentiation process of water and salt in regional scale.