Effect of climate on surface flow along a climatological gradient in Israel: a field rainfall simulation approach

A climatological gradient was selected in Israel to examine the effects of climate on surface flow and soil erosion. The gradient is composed of eight study areas located between the Dead Sea and the Galilee Mountains. Mean annual rainfall ranges from 100 mm year−1in the driest site to 900 mm year−1in the wettest site. Simulated rainfall experiments were performed in order to determine the main hydrological and erosional parameters. Data were recorded in 36 different plots after showers of 50 mm h−1rain intensity and 45–60 min duration. In the arid sites (<400 mm year−1) abundant runoff appeared on the soil surface very quickly, and the infiltration rates were very low. Erosion rates, sediment concentration and runoff salinity were very high. By contrast, on the wet sites (>500 mm year−1) runoff was very low due to the high infiltration rates and as a consequence erosion was negligible, while in the wettest area, local ponds were found at the beginning of the rain due to the hydrophobic response of the ecto-organic horizon. In general, ponding and runoff either failed to occur or were very delayed in the wet sites where the runoff coefficients were consequently very low.