Monitoring Urmia Lake Area Variations Using MODIS Satellite Data

Abstract

ABSTRACT Urmia Lake is a large hyper-saline lake located in the northwest of Iran. It plays an important role in the hydrology, climate and ecology of its surrounding regions. In recent years, the water level of Urmia Lake has been dropped significantly. This study investigates the seasonal and annual variations of the lake area from 2000 to 2011 using remote sensing data. MODIS imageries of Normalized Differential Vegetation Index (NDVI) were used to extract the water surface area of the lake. Results reveal a significant decline in the lake area during the last past 12 years. Analysis of the seasonal images shows that maximum and minimum areas of Urmia Lake usually occur in winter and autumn, respectively. This study confirms the successful application of MODIS-NDVI products for retrieving the variation of the large lakes area with an acceptable spatial and temporal resolution. Key words: Urmia Lake, Lake Area, MODIS, NDVI 1. Introduction Lakes as key elements of hydrologic cycle play an important role in meteorology, ecology and economy of their surrounding regions. Moreover, they are highly responsive to natural changes and anthropogenic impacts (Bai et al., 2011; Cretaux et al., 2011). One of the major threats to lakes ecosystem worldwide is the insufficient inflows due to the excessive use of water in the basins which in turn results in the lakes shrinkage (Ramsar Convention Secretariat, 2007). Such concerns are intensified in developing countries in semi-arid regions where regional water balance has been affected by intense abstraction of water in upstream rivers to meet agricultural demands (Bai et al., 2011). To achieve a better understanding of both human-induced and climatological impacts on lakes, it is a prerequisite to monitor principal characteristics of lakes such as water level and surface area (Cretaux et al., 2011).