A conceptual approach for evaluating the storage and release of contaminants derived from process based land degradation studies: an example from the Guadalentı́n basin, Southeast Spain

Abstract

The implications for land use change for the storage and release of contaminants in the Guadalentı́n catchment in SE Spain are considered. As part of a large project examining the impact of land use and climate change on arid land degradation, information has been collected on how soil properties, hydrology and vegetation are evolving on abandoned land. This information was used to characterise land degradation response units in two areas, one on slates the other on marls and limestone. The way in which changes and degradation processes on the different land units influence the ability of the land units to retain contaminants, as well as the risk of these being transported by erosion, was evaluated. It was concluded that in the slate area, the only areas of risk are in the valley bottom flood plains. Chemicals may be transported here by subsurface flow from the slopes. In the limestone and marl area there is a more general risk because of the high erodibility of the soil and because abandoned areas do not revegetate quickly following abandonment. Water from these overland flow producing areas may erode agricultural fields which are situated at the lowest position in the landscape. In the marl and limestone area, a comparison was made for the situation in 1957 and 1993. The situation today is different from 1957 because of larger field sizes and changed land-use. In both the old and current landscapes, there were significant stores of sediment in the agricultural areas that form potential sediment and contaminant sources.