California water law has traditionally treated groundwater and surface water as separate resources.

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Water scarcity commonly motivates managed aquifer recharge projects, but other factors can motivate recharge efforts, including in relatively water-rich areas. Surface water quality regulation has been a major driving force behind a large-scale recharge project in development in Virginia’s Coastal Plain region, where nutrient pollution from agricultural and urban sources has degraded the Chesapeake Bay’s ecosystems, leading state and federal regulators to require dischargers to reduce their nutrient contributions to the watershed over time. Hampton Roads Sanitation District is pursuing the Sustainable Water Initiative for Tomorrow, an innovative, multi-benefit initiative designed to address both nutrient pollution in the Chesapeake Bay watershed and regional groundwater overdraft in the Coastal Plain. When fully implemented, the initiative is expected to recharge approximately 100 million gallons per day of drinking-water quality, treated municipal wastewater into the Potomac Aquifer System through injection facilities located at five of the District’s wastewater treatment plants. As a result, the District expects to reduce its nutrient discharges from those plants by approximately 90%, enabling it to meet its own mandated nutrient limits while also generating nutrient credits that it can trade to other dischargers. Modeling suggests that the initiative will increase regional water pressure within the confined aquifer system, helping to combat groundwater overdraft and its negative impacts, including aquifer compaction and related land subsidence, falling water levels in wells, and saltwater intrusion. This case study provides insights into the influence of institutional context on managed aquifer recharge and on multi-benefit water resource projects more generally.

Traditional, limited purpose grey infrastructure has failed to address the world's interrelated water challenges. Improving water security will increasingly require more integrated responses. This paper examines large-scale green infrastructure (LSGI), planned natural or hybrid systems that materially affect water security at the watershed scale, as one such response. This paper examines key challenges for governing and financing LSGI, which hinder its broader use. We report on four case studies located in the United States where LSGI is being employed to improve water security. Through analysis of these case studies and related literature, we identify three themes important for LSGI governance: cost sharing, performance monitoring, and legitimization. First, we hypothesize that formal cost sharing based on the multiple benefits LSGI provides could enable wider adoption, but find that in these examples cost sharing is limited and informal. Second, our research suggests that expanding performance monitoring to encompass key secondary benefits could help clarify how the benefits and burdens of a project are distributed across stakeholders, facilitate cost sharing, and enhance project legitimacy. Finally, LSGI will require further legitimization – developing a broader perception that LSGI is an appropriate alternative or complement to grey infrastructure – to develop as a viable contributor to water security.

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