ABSTRACT
The mountain ridges are oriented from SW to NE and constitute successive barriers for the moist air coming from the seaside, predominantly from West. Rainfall increases with elevation and gradually decrease from West to East, being lower in the deeper valleys. Elevations of the irrigated fields vary along the region from 100m up to more than 1000m. These conditions lead to a large variation in the net irrigation water requirements along the region. The kriging estimation, widely used in earth and soil sciences [1] [2] [3], has been used for the spatial interpolation of that variable
2 Material and methods
2.1 Climatic data and soil water balance The climatic data available for the Tras-os-Montes region consisted of 106 rainfall data sets and 8 weather data sets with air temperature, relative humidity, sunshine duration and wind speed. The data sets refer to a ten-day time step and are 19 years long. All data sets have been tested for homogeneity and they were corrected when required. Missing values in the data sets were completed by a least square procedure using data from the nearest rainfall or weather station.
