Identification of Urban LID Implementation Opportunities for Groundwater Recharge

Abstract

GIS software was used to identify the geographic overlap of spatial datasets and then prioritize potential opportunities based on factors considered conducive to LID implementation. The resulting areas were presented in a series of LID bioretention opportunity maps for urban sub-watersheds within the Monterey Bay region. These maps identify potential areas for the implementation of bioretention features to achieve an increase in stormwater infiltration in urban areas overlying permeable soils with opportunities for groundwater recharge. Mapped areas are within Watershed Management Zone (WMZ) 1 or 4 (as defined by the California Central Coast Regional Water Quality Control Board), overlie a mapped groundwater aquifer, and drain to a stormwater collection system. Selected areas are prioritized into very high, high, moderate high, and moderate infiltration and recharge potential based on nine characteristics such as soil type, surface slope, and opportunity to recharge over drafted water supply aquifers. For nine catchments within five of the urban areas, infiltration potential was estimated based on average annual runoff and runoff during a design storm. The product of this analysis, the maps, GIS shapefiles, and a GIS modeling tool, were made available for partner agencies to use in their planning and implementation projects. The maps were subsequently used to identify, survey, and ultimately design LID retrofits on suitable parcels. MAPPING CRITERIA The primary goal of this effort was the creation of LID bioretention opportunity maps in urban sub-watersheds of the Monterey Bay region in California, USA. Mapping criteria focused on identifying potential infiltration and recharge areas within: Urban Area Boundaries, in Watershed Management Zone (WMZ) 1 or 4 (as defined by the California Central Coast Regional Water Quality Control Board), areas overlying a mapped Groundwater Aquifer, and where stormwater is managed via conveyance infrastructure. As an initial step in the mapping process, spatial data representing these four criteria were used to identify areas for prioritization. The areas identified by intersecting, or overlapping, these mapping criteria in GIS were then prioritized based on infiltration and recharge potential. The following is a summary of the four mapping criteria and how they were applied within one example urban area, the Scotts Valley Water District.