Présentations Colloques

    Oral Presentation
    Session 6.03: Innovative tools to improve understanding of groundwater recharge processes
    Ke-yu Zhao
    A study on the seasonal recharge patterns in the shallow groundwater area of semi-arid regions
    Due to the higher evaporation than precipitation in arid or semiarid regions, whether rainfalls can recharge to groundwater remains controversial. Moreover, the interaction of climate, hydrology, topography, soil properties and other factors makes the recharge process complex. This research aims to investigate recharge patterns with shallow groundwater in a semi-arid region in northwestern China by observing the dynamics of soil water and water table.** Our study site is situated in the low area of the Wudunao Watershed in the Ordos Cretaceous Basin. Soil moisture in two adjacent profiles and water table were monitored from May 2014 to November 2014. The groundwater depth ranged from 1.0 to 1.6 m in profile 1, and from 0.5 to 1.1 m in profile 2 near a depression. ** In profile 1, based on the responses of soil moisture at different depths to rainfalls, it was found that rainfall could not directly recharge to the water table from May to mid-September, but could do in late September, which lead to abrupt water table rises. It indicates that evaporation plays a major role on direct recharge because late September has the highest ratio of precipitation to evaporation. Although direct recharge did not occur in May through mid-September, rise of water table and soil moisture near the water table were associated with rainfalls. There should be other forms of groundwater recharge from precipitation. ** In profile 2 with shallower water table, we found precipitation could infiltrate and recharge directly to groundwater in May through mid-September. This demonstrates that rainfalls would recharge groundwater easily when the groundwater depth is shallow enough. Therefore, near-depression areas with shallow water table are ideal for precipitation recharge. ** Based on the field data, we simulate the effect of evaporation intensity, groundwater depth and soil properties on infiltration and direct recharge by Hydrus-1D. Numerical models demonstrate the seasonal variability of recharge patterns, as well as the control of evaporation and water table depth on precipitation recharge. **


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