Non-calibrated arid zone rainfall-runoff modelling

Two high-magnitude rainstorm floods were simulated using a distributed rainfall-runoff model of the 1400 km(2) arid catchment of Nahal Zin, northern Negev, Israel. No calibration with measured flow data was performed. The simulations used the October 1991 storm when almost the entire catchment was covered by high intensity rainfall as detected by rainfall radar, and a storm in October 1979 when only one ground station in the uppermost headwaters recorded heavy precipitation, while the majority of the catchment remained dry. For the latter event the distributed model served as a "runoff-rainfall model" to reconstruct the model input. The resulting two-dimensional description of the rainfall was then transferred to an ungauged tributary to produce a field-based scenario of a high magnitude flood. The results compared nicely to maximum observed discharges in the region. For the October 1991 event the model served as a tool to analyse the role that different major tributaries played during flood generation.