This is according to a new study conducted by the doctoral student Shay Sela under the guidance of Prof. Tal Saburai from the Department of Geography and Environmental Development at Ben-Gurion University of the Negev and Dr. Shmuel Assolin from the Volcanic Center
The physical soil crust plays an important role in keeping the rainwater that penetrates the soil throughout the rainy season. This is according to a new study conducted by the doctoral student Shay Sela under the guidance of Prof. Tal Saburai from the Department of Geography and Environmental Development at Ben-Gurion University of the Negev and Dr. Shmuel Assolin from the Volcanic Center, funded by the ISF and IALC funds.
As part of the study, the effect of a physical membrane layer on the surface of the soil on the seasonal water balance in a pasture in a semi-arid region was investigated. With the help of a physical model that simulated the conditions of an entire slope in the Gorel Hills area south of Lahavim and daily meteorological data from the past 32 years, the rate of water penetration into the ground and evaporation from it during the rainstorms and the time intervals between them is calculated.
It should be noted that in semi-arid areas, where the vegetation cover is sparse, a crust forms on the ground as a result of the impact of the raindrops (a physical crust - as opposed to a biological crust that also develops in these areas). The physical crust is tighter and less conductive than the ground on which it was formed. Therefore, the reference to it in science is usually as a factor that limits the penetration of water into the soil and as such that increases its flow along the slopes during rainstorms. However, the research shows that this membrane also significantly reduces evaporation fluxes from the ground during evaporation between rainstorms, a reduction which in most cases is compensation for the loss of water that did not penetrate.
This mechanism is of great importance to ecosystems, in light of the fact that in semi-arid regions there are relatively long drying periods between rainstorms. Later in the study, the hypothesis that the moisture preserved in the soil thanks to the physical crust compensates for changes in the rain and temperature regime in future environments will be tested. The research findings were accepted for publication in the hydrological journal Water Resources Research.
One response
The crust does reduce water infiltration when it rains, but in the desert rains are rare anyway, so the fact that the crust protects the water from evaporation is doubly significant in areas that are already arid. The question is how relevant it really is in real deserts like the Atacama or the Gobi. The desert in Israel receives an average of 50-100 mm of rain sometimes. In an extreme desert this amount is sometimes obtained only once in a hundred years.