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

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. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.