ABSTRACT

Soil salinity, being a major land degradation process in arid and semiarid regions, is spreading globally at a rate of two million hectares per year. Remote sensing data are widely used for detection and mapping of saline areas, hence was the objective of this study. Soil samples were collected from the field and analyzed in laboratory to check the salinity status. Results were interpolated and a salinity map of 2011 was developed. A satellite image of Landsat 5 Thematic Mapper of this area was classified, and a land cover map was developed containing different classes. Saline areas mapped from remote sensing (58.118 square kilometers (km²) and field data (highly saline 61 km²) were compared, which showed 65% similarity between these two methods. The same was applied on Landsat Images of 1992 and 2000 to calculate the change in the saline area over this time. The results showed an increasing trend (from 43.743 km² in 1992 to 58.118 km² in 2011) in saline area. A water table map of this area was generated from water table data and correlation (R²) between soil salinity and water table depth was calculated, which was fairly negative (R² = 0.7273 and R² = 0.6436) in moderately and highly saline categories based on electrical conductivity levels. It was concluded that remote sensing data are helpful only for detection and mapping highly saline areas (having salts on surface) and less suitable to detect where there is even slight vegetation cover.

摘要

土壤盐分是干旱和半干旱地区的主要土地退化过程，正以每年 200 万公顷的速度在全球蔓延。遥感数据被广泛用于盐碱地的探测和绘图，因此是本研究的目标。从田间采集土壤样品并在实验室进行分析以检查盐度状态。对结果进行插值，并绘制了 2011 年的盐度图。对该地区的 Landsat 5 Thematic Mapper 卫星图像进行了分类，并开发了包含不同类别的土地覆盖图。从遥感（58.118 平方公里（km ²）和实地数据（高盐度 61 km ^{2 ）测绘的盐碱区}) 进行比较，结果表明这两种方法之间有 65% 的相似性。在 1992 年和 2000 年的 Landsat 图像上也应用了同样的方法来计算这段时间内盐碱地的变化。结果表明，盐碱区呈增加趋势（从1992年的43.743 km ^{2到2011年的58.118 km 2}）。根据地下水位数据生成该地区的地下水位图，并计算出土壤盐分与地下水位深度之间的相关性（R ^{2 ），该相关性相当负（R 2}  = 0.7273 和 R ² = 0.6436）在基于电导率水平的中度和高度盐分类别中。得出的结论是，遥感数据仅有助于检测和测绘高盐度地区（地表有盐分），不太适合检测甚至有轻微植被覆盖的地方。