Water-table response to extreme precipitation events

Abstract

Extreme precipitation events (EPEs) will play a significant role in influencing soil–water and groundwater storage worldwide. We examined water-table depth (WTD) response to EPEs for 17 cases representative of soils and climate settings across the United States. Precipitation data from NOAA’s Precipitation Frequency Data Server were used for each case to characterize 1-day extreme precipitation events (EPEs) with annual exceedance probabilities of 0.1 % over an average baseline date range of 1981–2011. The inverse solution in the HYDRUS-1D modeling software was used to obtain the soil–water retention curve for each case. Non-EPE and EPE scenarios were modeled and compared to examine water-table displacement (ΔWTD) and recession time (trec). The ΔWTD ranged from 0.6 to 2.4 m across cases and were not directly controlled by EPE amount; instead, ΔWTD was inversely related to available porosity. Soils with low available porosity experienced large ΔWTD compared to soils with higher available porosity. In cases with larger diffusivity values, the modeled water table receded faster than in cases with smaller diffusivity values. This was because water-table recession times, trec, were inversely related to hydraulic diffusivity. For all cases, recession back to pre-EPE levels ranged from months to years suggesting an increased role by the unsaturated zone in buffering EPEs that should be considered in future EPE-groundwater modeling studies.