Effect of different vegetation type cover on the soil water balance in semi-arid areas of south eastern Spain

The simulated soil water balances under five vegetation types, using a developed model for the purpose, shows that the interception by plants represents 22 % to 35 % of annual rainfall (553 mm), in dry grasses and pine with grasses respectively. E-ta is the main outflow from the soil; being more than 80 % of net precipitation in pine plus shrub vegetation type. The bare soils and dry grasses show the highest deep drainage values (208 and 142 mm, respectively), however, is difficult to estimate what portion of this infiltrated water results in aquifer recharge. During the studied year one large rainfall event (134.6 mm) produced the main infiltration flow under all vegetation types, with a significant observed change in the aquifer piezometric level. A second simulation without this event, shows that the annual drainage in all types of cover was reduced. The soil water content evolution under each vegetation type, shows that the bare soils and dry grasses present the highest values. The most complex vegetation type, with high shrub biomass and pinus presents the highest consumption. Coefficients of determination for the regression of predicted daily soil water content on observed values were 0.65, 0.87, 0.90 and 0.93 for the pine reforestation with shrub understory; pine reforestation with dry grass understory; shrubland and dry grassland, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.