Magnitude-frequency analysis of water redistribution along a climate gradient in Spain

Banded patterns in soils and vegetation form part of important discontinuit ies on semi-arid slopes in Spain. At fine scales (<1 m) vegetation and well -structured soils are often located at the outer rim of small terracettes. Together they form banded patterns, distributed in a scattered way along co ntour lines. The objective of this study is to quantify the amount of surfa ce water redistribution at fine spatial scales for three areas in Spain, ha ving different rainfall regimes (290, 394 and 688 mm annual rainfall). Rain fall simulations experiments were carried out to determine runoff and infil tration characteristics of the bare and vegetated zones. The results of the se experiments are combined with an analysis of the rainfall magnitude-freq uency characteristics of the three area's. The combination of these two typ e of data has resulted in the calculations of a Redistribution Index (RI). The results showed a high variability in surface water redistribution from bare areas to banded vegetated zones. The combination of the infiltration c haracteristics at the different sites with the magnitude-frequency data of rainfall shows that most of the surface water redistribution originates fro m short storms with a duration of 10 min. The largest amount of redistribut ion during these events is found for areas having an intermediate rainfall regime with an annual rainfall of 394 mm. The Redistribution Index develope d during this study provides a rapid methodology that can be used to evalua te differences in the importance of surface water redistribution in differe nt banded vegetation structures at a regional scale. (C) 1999 Published by Elsevier Science B.V. All rights reserved.