Citation:

Sasidharan, S., S. Bradford, J. Simunek, AND S. Kraemer. Comparison of recharge from drywells and infiltration basins: A modeling study. JOURNAL OF HYDROLOGY. Elsevier Science Ltd, New York, NY, 594:125720, (2021). https://doi.org/10.1016/j.jhydrol.2020.125720

Impact/Purpose:

This modeling study compares the performance (infiltration, recharge, and storage) between a drywell and infiltration basin for the purpose of managed aquifer recharge (MAR). The idealized setup for an axisymmetric cross section with a constant head upper boundary condition allows for the efficient comparisons. Parameterization was informed by field measurements of the stormwater system (pond and drywell) at Fort Irwin, California. This research highlights how a drywell can be used in conjunction with, or as an alternative to, an infiltration basin when such a system is not feasible. The paper presents the following insights:• Infiltration and recharge increase with the area of an infiltration basin.• The arrival time of recharge from a drywell is shorter than an infiltration basin.• Five drywells can infiltrate and recharge more water than a 70 m diameter infiltration basin.• The benefit of a drywell still holds after 20 years of steady-state operation.• Low permeability subsurface layers can be bypassed using a drywell and infiltration basin in combination.

Description:

Drywells (DWs) and infiltration basins (IBs) are widely used as managed aquifer recharge (MAR) devices to capture stormwater runoff and recharge groundwater. However, no published research has compared the performance of these two engineered systems under shared conditions. Numerical experiments were conducted on an idealized 2D¿axisymmetric domain using the HYDRUS (2D/3D) software to systematically study the performance of a circular IB design (diameter and area) and partially penetrating DW (38 m length with water table > 60 m). The effects of subsurface heterogeneity on infiltration, recharge, and storage from the DW and IB under constant head conditions were investigated. The mean cumulative infiltration (μI) and recharge (μR) volumes increased, and the arrival time of recharge decreased with the IB area. Values of μI were higher for a 70 m diameter IB than an DW, whereas the value of μR was higher for a DW after 1-year of a constant head simulation under selected subsurface heterogeneity conditions. A comparison between mean μI, μR, and mean vadose zone storage (μS) values for all DW and IB stochastic simulations (70 for each MAR scenario) under steady-state conditions demonstrated that five DWs can replace a 70 m diameter IB to achieve significantly higher infiltration and recharge over 20 years of operation. Additional numerical experiments were conducted to study the influence of a shallow clay layer by considering an IB, DW, and a DW integrated into an IB. The presence of such a low permeable layer delayed groundwater recharge from an IB. In contrast, a DW can penetrate tight clay layers and release water below them and facilitate rapid infiltration and recharge. The potential benefits of a DW compared to an IB include a smaller footprint, the potential for pre-treatments to remove contaminants, less evaporation, less mobilization of in-situ contaminants, and potentially lower maintenance costs. Besides, this study demonstrates that combining both IB and DW helps to get the best out of both MAR techniques.

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