The effect of runoff collecting basins’ geometry on soil water evaporative losses Prof. Pedro Berliner, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University, Israel  

Water is a primary limiting factor to agricultural development in many arid and semi arid regions. In these regions, a large fraction of the annual rainfall is a result of a few intensive convective storms during which only a small fraction of the precipitation is absorbed by the soil. The fraction that is not absorbed by the soil flows to the lower laying parts of the land and is thus lost for plant production. The techniques of collecting runoff and conveying it to areas in which it can be ponded, is known collectively as runoff harvesting and microcatchments are one of the most popular systems. . In this system, runoff water is collected close to the area in which it was generated and conveyed to small dyke-surrounded plots in which trees/shrubs are planted and rely on the stored water in order to overcome the next dry season. The main objective of the work present herein was to estimate the effect the geometry of the collection area (shallow basin vs. deep trench) has on the efficiency of stored-water use.

The study was carried out during two years. During the first year one large runoff event was simulated and in the second year four small runoff events were simulated. ET and transpiration were monitored during both seasons. Evaporation was estimated as the difference between evapotranspiration obtained from soil water content monitoring and transpiration estimated by sap flow measurement. Evaporation from micro-catchments was significantly higher than evaporation from trenches for both seasons.