Runoff generation on abandoned fields in the Central Ebro Basin. Results from modelling

Abstract

The results from several rainfall simulations performed on two abandoned fields of different ages in the Central Ebro Depression have been analysed by application of the physically based hydraulic model HILLFLOW 1D. The data gained by the simulations was used to parameterise the model. Afterwards, the runoff generation characteristics were determined by simulation of different rainfall intensities and different macroporosities of the soil. The young fallow land shows a minimum intensity for runoff generation of 6 mm h-1. An increase of the rainfall intensity leads rapidly to a growing runoff coefficient, being the value modelled for 30 mm h-1 nearly the same as the simulated one (40 mm h-1). Another con - clusion of the simulations and their modelling is the homogeneity of the soils on the young fallow land, with no macroporosity all over the profile. On the other hand, the rainfall simulations and the modelling on the old fallow land show a high variability of rainfall-runoff response patterns, strongly conditioned by the presence of macropores. They are distributed very irregularly throughout the soil of the old fallow land. In both cases, water infiltrates only little into the soil matrix, for that measures for enhancing soil hydraulic properties are needed.