Escorrentía y erosión en los suelos del desierto de Judea

Abstract

The Judean Desert soils are characterised by high runoff rates, short times to ponding and runoff (1' 13" and 2' 03" respectively), low steady state infiltration rates (7 mm h'1) and very high angles of runoff curves, reaching the stability of the runoff rates earlier than 20 minutes. The erosion rates are very high, shown by the large volumes of runoff collected due to the high erodibility of soils, affected by the grazing during millenniums. On the contray, the salinity of the runoff is very low in relation with the salts accumulated in the soils.The soils less affected by grazing (Ma'ale Adumin), produce large runoff volumes, although the milkeness was very low. This is due to the positive effect of the surficial crust and to the abundance of rocks fragments in the reduction of the erodibility of the soils. The soils more affected by grazing (Mishor Adumin) show disturbed crusts and dust accumulation on the surfaces, causing higher runoff sediment concentrations (even 10 g l-1), erosion rates (400 g m2 h-1) andrunoff coefficients (0,90) to ocurr.The results demonstrate the importance of the biological crust for the hydrology and erodibility of soils in semiarid environments, and for the posibility of the surface -hortonian- overland flow during the high intensity thunderstorms to ocurr. The anthropic use of the land, in this case grazing, modifies the mechanisms that transform the rainfall into runoff, and induce erosion to ocurr.