Maximal discharges observed in Israel

Abstract

Maximal discharges observed in Israel since 1938 are plotted on a log-log paper against the catchment area of the measuring sites. Four envelope lines, parallel to one another, are drawn on the paper. The formula of these lines is Q=c A^0.83, in which Q is the maximal observed discharge, in m³/sec, A is the catchment area, in km², and c is an empirical coefficient, in m³/sec km^1.65. The value of c varies from 1.7 to 4.5 units, depending on the precipitation and the lithology of the watershed. Higher discharges are observed where the mean annual depth of the precipitation is lower. With respect to the lithological units found in Israel, the highest discharges are observed where the lithology is of thin deposited limestone and the surface slopes are steep. The lowest maximal discharges are observed where the lithology is heavy deposited limestone and dolomite, or conglomerates. No high discharges are observed from watersheds where the lithology is Holocenean sand. In general, impervious, steeply sloped surfaces generate higher discharges than pervious or mildly sloped surfaces.