Crop water requirement estimation of wheat cultivated fields by remote sensing and GIS

In water resources and hydrological studies, transpiration from plants and evaporation from the underlying soil is an important factor for estimating irrigation water requirements when planning irrigation systems, especially in arid and semi-arid conditions of South-Eastern Anatolia in Turkey. The aim of the study is to investigate the water requirement for wheat fields cultivated on different soil types by estimating the actual crop evapotranspiration of wheat crop via Remote Sensing (RS) and Geographical Information System (GIS) techniques. The data used in this study was obtained from selected real-time monitoring areas for wheat cultivated fields located on the area of South-Eastern Anatolia Region. SPOT 5 satellite images that were acquired at the growing season of wheat crop were used to determine the Normalized Difference Vegetation Index (NDVI), Modified Soil Adjusted Vegetation Index (MSAVI) and to generate the crop coefficients (K_C) for each month of wheat crop season. As a result, the MSAVI values were found to have a high correlation with K_C values (R² ~ 0.89) for both selected wheat cultivated fields with different soil types in Hilvan and Akcakale districts of Sanliurfa province. The pixel-wise K_C values of these fields were computed from corresponding MSAVI maps by using the developed empirical regression relationships of MSAVI. These K_C values of wheat crop from different fields were generated by using their correlation with remote sensing based NDVI and MSAVI values. Preliminary results have shown that water demands may vary for cultivated wheat fields on different soil types having different land use capability classes.