Environmental assessments of aquifer storage and recovery for decentralized wastewater management

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During FY2022, we utilized an integrated surface-subsurface flow modeling approach to evaluate the effectiveness of drywells in reducing urban runoff at a catchment scale. A 3D model with HydroGeoSphere was developed, characterizing a synthetic unconfined aquifer covered by a layer of low-permeability materials. Sensitivity analyses of parameters such as land surface conditions, aquifer properties, drywell designs, and rainfall conditions were performed. Model results indicated that drywells are more effective in reducing runoff when the land surface has a higher Manning roughness coefficient or the aquifer material has a higher hydraulic conductivity. To achieve optimal performance, drywells should be situated beneath drainage routes that have high runoff flux. Increases in drywell radius or depth enhance the infiltration capacity, but deeper drywells can contaminate groundwater through infiltrating stormwater. Drywell performance declines with higher rainfall intensity, emphasizing the need for local rainfall intensity, duration, frequency (IDF) data to inform the design level of drywells in specific catchments