Abstract
AbstractSurface evaporation in arid regions determines the fraction of rainfall that remains to support vegetation and recharge. The surface evaporation capacitor approach was used to estimate rainfall partitioning to surface evaporation and leakage into deeper layers. The surface evaporation capacitor estimates a soil‐specific surface evaporation depth and critical storage capacitance that defines rainfall events that exceed local capacitance and result in leakage into deeper layers protected from surface evaporation. A decade‐long record of hydrologic observations in deep and barren lysimeters near Las Vegas revealed the dominance of a few large rainfall events in generating leakage and increasing interannual soil water storage. The surface evaporation capacitor was used to estimate mean annual surface evaporation and leakage protected from surface evaporation in all arid regions globally. About 13% of arid region rainfall contributes to soil water storage (in the absence of vegetation), similar to 11% found in the lysimeter study.
Highlights
Deserts cover about one third of the global land surface, hosting unique ecosystems that are adapted to water limitations
About 13% of arid region rainfall contributes to soil water storage, similar to 11% found in the lysimeter study
These results show a difference between measured cumulative evaporation (930 mm) and cumulative rainfall (1,050 mm) for the decade of about 120 mm that contributed to soil water storage in the lysimeter
Summary
Deserts cover about one third of the global land surface, hosting unique ecosystems that are adapted to water limitations. Such regions are characterized by high values of annual potential evapotranspiration ET0 that exceed the annual rainfall P (with aridity index P/ET0 < 0.2 for arid regions) and where most rainfall evaporates locally back to the atmosphere. The fraction of rainfall water that percolates into deeper soil layers and become protected from surface evaporation is a complicated function of rainfall patterns, topography, vegetation, and soil texture (Gee et al, 2005; Wythers et al, 1999). The SEC model considers water dynamics within this evaporation‐active soil layer only (whose depth is a function of intrinsic soil properties) without discretization of the soil profiles into different layers
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