Is Annual Recharge Coefficient a Valid Concept in Arid and Semi-Arid Region?
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Abstract. Deep soil recharge (DSR) (at depth more than 200cm) is an important part of water circulation in arid and semi-arid regions. Quantitative monitoring of DSR is of great importance to assess water resources and study water balance in arid and semi-arid regions. Simple estimates of recharge based on fixed fractions of annual precipitation are misleading because they do not reflect the plant and soil factors controlling recharge. This study used a typical bare land on the Eastern margin of Mu Us Sandy Land of China an example to illustrate a new lysimeter method of measuring DSR underneath bare sand land in arid and semi-arid regions. Positioning monitoring was done on precipitation and DSR measurement underneath mobile sand dunes from 2013 to 2015 in the study area. Results showed that use of a constant recharge coefficient for estimating DSR in bare sand land in arid and semi-arid regions is questionable and could lead to considerable errors. It appeared that DSR in those regions was influenced by precipitation pattern, and was closely correlated with spontaneous heavy precipitation (defined for an event with more than 10mm precipitation) other than the average precipitation strength. This study showed that as much as 42% of precipitation in a single heavy precipitation event can be transformed into DSR. During the observation period, the maximum annual DSR could make up to 24.33% of the annual precipitation. This study provided a reliable method of estimating DSR in sandy area of arid and semi-arid regions, which is valuable for managing groundwater resources and ecological restoration in those regions.
