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Groundwater recharge and microbial water quality from drywells
Citation:
Sasidharan, S., S. Bradford, J. Simunek, AND S. Kraemer. Groundwater recharge and microbial water quality from drywells. 2019 AGU Fall Meeting, San Francisco, CA, December 09 - 13, 2019.
Impact/Purpose:
Water has a strong influence on the economic growth of nations. Many arid and semi-arid urban regions of the world face challenges in maintaining water quality and quantity to meet its growing population demand. A drywell is a vadose zone infiltration device that is increasingly used for stormwater management and enhanced aquifer recharge. However, only limited research has quantitatively examined groundwater recharge and contaminant transport from a drywell, especially in the presence of subsurface heterogeneity. Numerical and field experiments were therefore conducted to characterize long-term infiltration and recharge behavior of drywells.
Description:
Water has a strong influence on the economic growth of nations. Many arid and semi-arid urban regions of the world face challenges in maintaining water quality and quantity to meet its growing population demand. A drywell is a vadose zone infiltration device that is increasingly used for stormwater management and enhanced aquifer recharge. However, only limited research has quantitatively examined groundwater recharge and contaminant transport from a drywell, especially in the presence of subsurface heterogeneity. Numerical and field experiments were therefore conducted to characterize long-term infiltration and recharge behavior of drywells. Numerical experiments were conducted using the HYDRUS (2D/3D) computer software under steady-state and transient head boundary conditions to evaluate different drywell designs to capture, infiltrate, and transmit stormwater through the vadose zone, systematically study the influence of subsurface heterogeneity on groundwater recharge and microbial water quality. Subsurface heterogeneity was described by generating stochastic realizations of soil hydraulic properties with selected variance (σ) and horizontal (X) and vertical (Y) correlation lengths. Steady-state and transient experiments were conducted to determine the cumulative infiltration volume (I), cumulative recharge volume (R), area of recharge, recharge flux, and initial arrival time and location. The value of I and R increased with σ and X but decreased with Y. The initial arrival time increased with X and decreased with σ and Y. Interestingly, the value of initial arrival location for both recharge water and contaminants was highly correlated to the subsurface heterogeneity and varied from 0-11 m away from the drywell center in the horizontal direction. The presence of many laterally extending lenses enhances infiltration and leads to lateral spreading, which delays the vertical movement and thus initial recharging. In contrast, the presence of highly permeable vertical lenses enhances the faster vertical movement of water and microbial contaminants and thus an early arrival time to groundwater. This information provides critical information on recharge water quality and quantity.