Hillslope hydrology water harvesting and areal distribution of some ancient agricultural systems in the northern Negev desert.

Ancient agricultural fields, based on hillslope runoff farming, have been discovered in the Negev Highlands. Stone mounds and stone strips spread over the hillslopes have been associated with some of the agricultural practices. Studying these features, previous workers presented a theory stressing the negative role of stone cover and high slope angles in runoff generation. However, a detailed analysis of runoff-collecting conduits shows that most conduits are located within the steepest part of rocky and very stony slopes, whereas extensive gentle and stoneless loessial slopes are generally devoid of ancient agricultural farms. The location of the conduits, as well as the areal distribution of ancient fields, are explained based on detailed hillslope hydrological studies coupled with an analysis of soil properties along rocky and loessial slopes. The explanation stresses the positive role of massive bedrock outcrops in increasing runoff generation and improving desert environment. It also draws attention to the negative role played by a contiguous soil cover which, in an arid area, increases environmental aridity. The general theoretical implications of the results are discussed in detail in light of evidence from fields in which physical environment plays an important role.-Author