Water stress during crop growth, even during short periods of a couple of weeks, is a major cause of yield reduction. The complexity in defining the magnitude of such water stress is due to diversity of crops grown in a given location, variability in soil type and conditions, spatial variability of rainfall, delay in timely of agriculture, and diversity in crop management practices. The problem associated with drought is a recurrent feature in Mongolia. In fact drought is a significant environmental problem too as it is caused by less than average rainfall over a long period of time. In Mongolia about 95 percent of total wheat sown area of the country is rain fed. Mongolian grain productivity needs to occur in an environmentally sustainable manner.

Remote sensing technology is an economical and promising tool for obtaining land surface parameters. A drought index based on land surface temperature should be more efficient than those based on NDVI.

This study was investigates the use of remote sensing data for essential factors for crop growth in cropland area of Mongolia. In this case were used on cloud-free Landsat-7 ETM+ image of Tsagaannuur district of Selenge province, Mongolia for land surface temperature retrieval.

In conclusion, remotely-sensed water stress index provided a useful tool for the evaluation of crop water status especially that of wheat in Tsgaannuur, Mongolia and could be useful for rain fed cropland area and irrigation scheduling.