Stormwater Non-Potable Beneficial Uses: Modeling Groundwater Recharge at a Stormwater Drywell Installation

Abstract

The harvesting of urban stormwater to supply non-potable water demands is emerging as a viable option, amongst others, as a means to augment increasingly stressed urban water supply systems. A main objective of this Water Environment Research Foundation (WERF)/EPA funded project is to show how currently available models and other tools can be interactively used to calculate the benefits of stormwater beneficial uses. For the past several years, the city of Millburn has required cisterns to accommodate the flow from newly developed areas. Currently, these are infiltration cisterns for groundwater recharge, but water storage cisterns for irrigation is becoming increasingly of interest. In this stage of the project, this paper presents land use characteristics and soil parameters to fit an appropriate model to the infiltration data which are important inputs for the WinSLAMM model. The Horton and Green-Ampt infiltration equations are two widely used methods to describe infiltration capacities at small stormwater infiltration controls. In this paper, the Horton and the Green-Ampt parameters were determined for actual events at dry well recharge sites in Millburn, NJ. The results indicated that the Horton equation better fits the actual data, however, the fitted equation parameters did not always compare well to prior published parameters from the literature. Other elements of this WERF/EPA supported project include a broad review of US and international regulations pertaining to stormwater beneficial uses, many case study summaries, and descriptions of likely stormwater sources having acceptable quality that would minimize any adverse effects. Later project activities will involve extensive modeling of stormwater beneficial use opportunities at many US locations, including the development of production functions that can enable local water managers to make top-level evaluations of this water source.