Using a GIS to develop distributed stormwater collection systems linked to managed aquifer recharge
Earth and Planetary Sciences Department, University of California
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We are completing a regional geographic information system (GIS) analysis of Santa Cruz and northern Monterey Counties, CA to assess conditions amenable to distributed stormwater collection linked to managed aquifer recharge (DSC-MAR). Many groundwater aquifers in this region are experiencing chronic overdraft and are at risk of contamination and seawater intrusion. In the face of ongoing drought, communities and water supply agencies across CA are struggling to develop secure and sustainable water supplies for long-term municipal, agricultural, environmental, and other needs. Enhanced groundwater storage is an important part of this effort in many basins and can be implemented with a variety of techniques such as infiltration basins, dry wells, or flooding of agricultural fields. Our project is especially timely because California’s recently-enacted Sustainable Groundwater Management Act requires the creation of groundwater sustainability agencies and the development and implementation of basin management plans. Our analyses focus specifically on the distributed collection of stormwater runoff, a water source that has typically been treated as a nuisance or waste, from catchments having areas of 100 to 1000 acres. This part of our project is a GIS analysis using surface and subsurface data. Developing complete and accurate data coverage for our study region requires considerable effort to locate, assemble, co-register, patch, and reconcile information from many sources, scales, and projections. We have complete spatial coverage for many kinds of surface data, including surface geology, soil infiltration capacity and slope, but subsurface data are limited in lateral extent. Sites that are most suitable for DSC-MAR have high soil infiltration capacity, are well-connected to an underlying aquifer with good transmissive and storage properties, and have space to store additional water. Additional considerations include infiltration method, slope, and land use and access. Based on initial consideration of surface data, much of the study region appears to be suitable or highly suitable for MAR (in the top third of the rating system), including sites that are used for agricultural production, but there is considerable spatial heterogeneity based on the distribution of shallow soils and bedrock geology. Our GIS work is linked to regional runoff modeling to assess where there is a confluence of good conditions for MAR and likely supply of stormwater runoff (please see related poster by Young et al.).