A simulation of soil water content based on remote sensing in a semi-arid Mediterranean agricultural landscape

Abstract

This paper shows the application of a water balance based on remote sensing that integrated a Landsat 5 series from 2009 in an area of 1,300 km2 in the Duero Basin (Spain). The objective was to simulate the daily soil water content (SWC), actual evapotranspiration, deep percolation and irrigation rates. The accuracy of the application is tested in a semi-arid Mediterranean agricultural landscape with crops over natural conditions. The results of the simulated SWC were compared against 19 in situ stations of the Soil Moisture Measurement Stations Network (REMEDHUS), in order to check the feasibility and accuracy of the application. The theoretical basis of the application was the FAO56 calculation assisted by remotely sensed imagery. The basal crop coefficient (Kcb), as well as other parameters of the calculation came from the remote reflectance of the images. This approach was implemented in the computerized tool HIDROMORE+, which integrates various spatial databases. The comparison of simulated and observed values (at different depths and different land uses) showed a good global agreement for the area (R2=0.92, RMSE=0.031 m3 m-3, and bias=-0.027 m3 m-3). The land uses better described were rainfed cereals (R2=0.86, RMSE=0.030 m3 m-3, and bias=-0.025 m3 m-3) and vineyards (R2=0.86, RMSE=0.016 m3 m-3, and bias=-0.013 m3 m-3). In general, an underestimation of the soil water content is noticed, more pronounced into the root zone than at surface layer. The final aim was to convert the application into a hydrological tool available for agricultural water management.