A landcover change study of takyr surfaces in Turkmenistan

The shortage of fresh water in Turkmenistan may be partially alleviated by runoff water from takyrs. However, anthropogenic degradation of takyrs over the past few decades has reduced their efficacy as catchment areas. The main goal of this study was to map the spatial extent of takyrs and their change over time. Digital image processing of Landsat MSS and Landsat 7 ETM+ images were used to identify, map and classify the takyrs and estimate their overall area and degradation rates. Thereafter, a change detection procedure was applied. Results retrieved from Landsat MSS images of southern Turkmenistan (1972-1975) showed a total area of non-degraded takyr surfaces of similar to 20,000 km(2), whereas those from Landsat 7 ETM+ images (2002-2003) showed a total non-degraded takyr area of similar to 16,000 km(2). These include similar to 8000 km(2) which were degraded and similar to 4000 km(2) that were only detected by the ETM+ due to its improved spectral resolution. Accuracy was assessed by comparing the Landsat results with higher spatial resolution images of QuickBird. Additional ground points located with GPS measurements validated the classification results. We were thus able to assess the takyr areas degraded over the past decades, and find similar to 16,000 km(2) of non-degraded takyrs suitable for water harvesting. (C) 2011 Elsevier Ltd. All rights reserved.