The eco-hydrological feedback as constraints on the development of drylands

Under arid (dryland) conditions where the usual rain amounts fall short of the moisture deficit in the surface layers, the occurrence of surface flows is a necessary pre-requisite for the occurrence of groundwater recharge at selected infiltration sites. These surface flows at the same time nourish a variety of plants and biota along the flowpaths, which in turn affect both the quality and quantity of the region's water resources, especially the salinity buildup. Given these circumstances, both the local recharge as well as the flushing of surface salinity and pollutants depend critically on land use and are extremely sensitive to any change which affects the rain/runoff relationship. With increasing population pressures development relies to an ever increasing extent on the import of extraneous water. Management is then faced with the additional problem of water excesses beyond the natural drainage capacity of the arid system on a year round basis and the resulting ecological changes.