Morphological changes in the Aral Sea. Satellite imagery and water balance model.

Kurzfassung

The Aral Sea, once the world’s fourth largest lake, has suffered a dramatic loss of both area and volume, as a result of greatly reduced river inflow brought about by increasing irrigation (mainly of cotton and rice) along the two rivers, Amu Darja and Syr Darja, that flow into it. The ecological consequences are severe and have been discussed in a variety of scientific publications (Micklin, 1991 and 2000, Giese, 1998, Letolle, & Mainguet, 1996). Satellite images have helped to monitor and document the desiccation process and to describe the associated morphological changes. This includes changes of the water body itself as well as the related changes of the surrounding environment and plant communities, such as the newly formed desert areas like the so-called “Aral Kum”. Low spatial resolution data such as NOAA-AVHRR has proven to be valuable to monitor the desiccation on a frequent basis. The use of high resolution satellite data has been limited for morphological change studies due to higher costs (Resurs-MSU-SK/E, Landsat-TM) and only partial coverage of the lake surface. New satellite systems such as Terra-MODIS are useful because of full coverage of the lake, easy access on a daily basis and provision to researchers at no cost. Besides remote sensing data, GIS modelling techniques have proven to be a useful tool for forecasting the desiccation process of the Aral Sea under specific circumstances. Several probable water inflow scenarios have been assumed to forecast the future desiccation of the lake. Further investigations will include automatic change detection and automated monitoring of the desiccation process.