The effects of a dry sand layer on groundwater recharge in extremely arid areas: field study in the western Hexi Corridor of northwestern China | Les effets d’une couche de sable sec sur la recharge des eaux souterraines dans des zones d’extrême aridité: cas d’étude dans le corridor occidental de l’Hexi dans le nord-ouest de la Chine Los efectos de una capa de arena seca en la recarga de las aguas subterráneas en zonas extremadamente áridas: estudio de campo en el Hexi Corridor occidental del noroeste de China 极端干旱地区干沙层对地下水补给的影响:中国西北河西走廊西部野外试验 O efeito de uma camada de areia seca na recarga de água subterrânea em zonas extremamente áridas: ensaio de campo no Corredor Hexi ocidental no noroeste da China
2016
Sun, Peng | Ma, Jinzhu | Qi, Shi | Zhao, Wei | Zhu, Gaofeng
Evaporation capacity is an important factor that cannot be ignored when judging whether extreme precipitation events will produce groundwater recharge. The evaporation layer’s role in groundwater recharge was evaluated using a lysimeter simulation experiment in the desert area of Dunhuang, in the western part of the Hexi Corridor in northwestern China’s Gansu Province. The annual precipitation in the study area is extremely low, averaging 38.87 mm during the 60-year study period, and daily pan evaporation amounts to 2,486 mm. Three simulated precipitation regimes (normal, 10 mm; ordinary annual maximum, 21 mm; and extreme, 31 mm) were used in the lysimeter simulation to allow monitoring of water movement and weighing to detect evaporative losses. The differences in soil-water content to a depth of 50 cm in the soil profile significantly affected rainfall infiltration during the initial stages of rainfall events. It was found that the presence of a dry 50-cm-deep sand layer was the key factor for “potential recharge” after the three rainfall events. Daily precipitation events less than 20 mm did not produce groundwater recharge because of the barrier effect created by the dry sand. Infiltration totaled 0.68 mm and penetrated to a depth below 50 cm with 31 mm of rainfall, representing potential recharge equivalent to 1.7 % of the rainfall. This suggests that only extreme precipitation events offer the possibility of recharge of groundwater in this extremely arid area.
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