Effects of Topgraphic Attributes and Water-Table Depths on the Soil Salinity Accumulation in Arid Land

Abstract

Soil salinity is a serious environmental problem, particularly in semi-arid and arid regions. Its accumulation is controlled and aggravated by a combination of several factors such as human activities, climatic conditions, landform variability and water table depths. This research aims to analyze the influence of the topographic attributes variability and the depths of the water table on soil salinity accumulation in arid landscape. Moreover, the maps of soil types (properties) and lithology were also considered to support the findings of this work. Topographic attributes (i.e. elevations, slopes, orientations, flow direction and flow accumulation) were derived from the SRTM-V4.1 DEM with 30 m pixel size. While, the water table map was established applying ordinary Kriging interpolation based on a total of 200 hydraulic head measurement points recorded over the study area represented by centre and east parts of the state of Kuwait. All these data were integrated in GIS environment for spatial analysis. A total of 30 samples were randomly selected and localized using a DGPS to statistically analyse <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(p &lt; 0.05)$</tex> the relationship among soil salinity, elevations variability, and water table depths. The results demonstrate that these variables associated with high temperature exhibited a significant impact on the spatial distribution and accumulation of soil salinity in arid landscape. Generally, areas at a relatively high altitude <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(35 \mathrm{m}\leq)$</tex> with hard bedrock and deep water table (12 m BGL <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq$</tex> ) are less susceptible to salinity <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(\leq 10 \text{dS} \cdot \mathrm{m}^{-1}\right)$</tex> . While, areas at a low altitudes <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\leq 8.0\mathrm{m}$</tex> MSL), feeble slopes ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq$</tex> 5%) and groundwater table near to the soil surface <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\leq 1.00\mathrm{m}$</tex> below ground level) exacerbating the salt accumulation in the soil through capillary movement and subsequent evaporation. Moreover, in such low areas, the absence of an adequate drainage network contributes significantly to waterlogging. Consequently, the intrusion and emergence of seawater at the surface, coupled with high temperature and high evaporation rates, contribute extensively to the salt accumulation in the soil. Furthermore, statistical analysis shows a significant inverse correlation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{R}=_{-}0.7)$</tex> demonstrating the close relationship between soil salinity accumulations, topographic attributes and water table depths.