2004. A daily water balance estimate for climate risk evaluation at a local scale

Abstract A methodology for calculating a soil-water balance based on climatological and pedological data of Sardinia (Italy) is presented. Daily temperature and rainfall data from reference period 1971-2000 were spatially interpolated on a 10 km x 10 km cell grid to obtain a set of homogeneously distributed values. Pedological information of Sardinian soils were used to characterize the entire territory of Sardinia in terms of available water content (AWC) and soil depth. Reference evapotranspiration values (ETo) were estimated using the Hargreaves method and actual evapotranspiration estimates (ETa) were calculated as function of soil water content for each grid cell. A simplified soil water balance was calculated for each grid point and year to determine the average daily soil water content over the thirty-year period. Climatic risk was evaluated considering the number of days when soil water content was below 50% of available water content threshold for each year of the 1971-2000 period. Results show a wide variability of interannual climatic and water deficit conditions throughout the region. Maps of spatial distribution of drought conditions show that the dryest years were from 1996 to 2000. During this 5-year period, about 60% of the Sardinian territory was affected by severe climatic conditions which determined high climatic risk for agricultural areas.