Distributed Stormwater Collection and Managed Aquifer Recharge

Distributed Stormwater Collection and Managed Aquifer Recharge

CC Report Cover cropped
Data and products associated with California State Coastal Conservancy project 13-118, "Regional Managed Aquifer Recharge And Runoff Analysis In Santa Cruz County, California"

Distributed Stormwater Collection and Managed Aquifer Recharge (DSC-MAR) is a landscape management strategy that can help to reduce aquifer overdraft and maintain long-term water supply reliability.
DSC-MAR targets relatively small drainage areas (generally 100-1000 acres) from which stormwater runoff can be collected to infiltrate 100-300 acre-feet of water per year. Infiltration can be accomplished in surface basins, typically having an area of 1-5 acres, or potentially through flooding of agricultural fields or flood plains, use of drywells, or other strategies. Smaller projects might provide additional benefit, but unit costs are likely to be somewhat greater. Larger projects may require more infrastructure and/or maintenance costs.

In 2014, the RCDSCC partnered with UCSC’s Hydrogeology Group, securing support from the California State Coastal Conservancy, to complete a Regional Managed Aquifer Recharge (MAR) and Runoff Analysis for Santa Cruz and Northern Monterey Counties, and to develop information and decision support tools to optimize storm runoff collection and MAR project implementation. The focus of this project is to quantify, in a documented and self-consistent way, where there is the highest potential for both suitable hydrologic conditions and enough stormwater runoff to justify implementation of a field project. Results should be most immediately beneficial for the region for which analyses were completed, but this project can also serve as a template for other parts of the state, where a similar approach could be applied.

On this page you can download publicly accessible products from this analysis, including: GIS datasets, maps, input data, data processing descriptions, and precipitation and runoff model outputs to: a) identify and prioritize suitable areas for groundwater recharge, and b) evaluate hydrologic response (runoff vs. infiltration) under different climate scenarios.

Why do we need DSC-MAR?
  • Climate change threatens California's coastal watersheds, bringing more frequent extreme precipitation events, and an associated increase in runoff and reduction in infiltration and groundwater recharge.
  • Changes in land use and increased freshwater demand are placing increased pressure on limited groundwater supplies.
  • California lacks adequate surface storage for collection of stormwater runoff, although there is abundant subsurface storage in many parts of the state.
  • Over the last two decades California has increased its statewide water supply deficit, much of it as a result of groundwater overdraft.
  • This is particularly critical on California's central coast, where ~85% of freshwater demand is met by groundwater.
  • The central coast is also virtually off the grid in terms of large scale regional water transfers, relying almost entirely on local groundwater resources.
  • In 2015 DWR designated multiple groundwater basins in California's central coast as being in a state of "critical aquifer."
  • Groundwater overdraft can lead to numerous undesirable conditions including: seawater intrusion, land subsidence, permanent loss of aquifer storage, loss of stream and wetland flow, damage to riparian habitat, and degradation of water quality.
  • Improving groundwater conditions yields long-term benefits to both water supply and quality, positively impacting aquifers and associated aquatic systems, habitats, species and economic activities that depend on them.

Regional Managed Aquifer Recharge (MAR) and Runoff Analysis for Santa Cruz and Northern Monterey Counties

Where are the best places to recharge groundwater?
MAR Suitability Analysis: This part of the project examined a series of surface and subsurface data sets to identify locations that could most effectively recharge groundwater within the study area. MAR suitability was assessed using a geographical information system (GIS) framework for collection, creation, modification, classification and manipulation of existing and new spatial and temporal data sets, to help guide the placement of implementation projects. Of course, hydrologic suitability is only part of the story, but it is an important part, and can be used as a "screen" to assess where to put effort initially to achieve the greatest and most rapid benefit. Many other factors must be considered before implementing a project, including (but not limited to): available water supply, water quality, available land and associated land use, interest among landowners and tenants, availability of incentives and resources for both capital costs and operation/maintenance of MAR systems, ease of measurement to document benefits, governance and management responsibility, comparison to alternatives, and permitting.

Where and how much storm runoff can be collected for groundwater recharge?
Runoff and Precipitation Modeling: Stormwater runoff was analyzed based on past, current and potential future precipitation and land use conditions. Runoff distribution and collection potential for individual catchments within the study area were assessed using the Precipitation Runoff Modeling System (PRMS), a publically available watershed model developed by the U.S. Geological Survey. PRMS has been extensively tested and is a widely used and accepted tool for assessing the impacts of changes in climate and land use on hydrologic basin response. PRMS model inputs consist of numerous spatially distributed data sets, including some of the same datasets developed for MAR suitability analyses, along with historic precipitation data to model how much runoff can be expected at any given location under specific precipitation conditions, based on soil, topography and land cover/use characteristics.

Project region and subregions:
Project region: Although this study was originally developed to provide information mainly to Santa Cruz County, CA, the study region was extended so as to include the complete drainage area that generates stormwater (hillslope) runoff flowing into Santa Cruz County, and the region overlying the Pajaro Valley Groundwater Basin, part of which is located in southern Santa Cruz County, but also including northern Monterey County. Hydrologic drainage regions included in this study were those delineated by the USDA for Santa Cruz County, comprising four subregional basins. The first set of data listed below (and available for download) includes GIS files that delineate the complete project region and the four drainage subregions.

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Downloadable Materials

pdfFinal Report (without figures)

pdfFigures Chapter 1 - Scope of Analysis

pdfFigures Chapter 2 - Digital Elevation Model (DEM) and PRMS inputs

pdfFigures Chapter 3a - Elevation and soil maps

pdfFigures Chapter 3b - Bedrock geology, aquifer characteristics and MAR suitability maps

pdfFigures Chapter 4a - PRMS calibration and validation data, precipitation maps, precipitation and runoff averages by climate scenario

pdfFigures Chapter 4b - PRMS outputs, hillslope runoff maps

 

1.       MAR Suitability Analysis

Input Data and Final Products
GIS Coverage Geographic Boundary (See project area and sub-regions map)
Full Project Area PVGB MSCC SLRB NoCo
Project Regions SCC + No MC Pajaro Valley Groundwater Basin Mid Santa Cruz County San Lorenzo River Basin North Coast
Shape files and outlines pdfProject Regions

zipFull Project Area GIS files
zipPVGB region GIS files zipMSCC region GIS files zipSLRB region GIS files zipNoCo region GIS files
Surface Characteristics SCC + No MC Pajaro Valley Groundwater Basin Mid Santa Cruz County San Lorenzo River Basin North Coast
Elevation (DEM) INPUT

pdfInputCoveragePatch

zipAMBAG 3m DEM

zipUSGS 3m DEM

zipUSGS 10m DEM

PRODUCTS

pdfDEM FullProject

zipDEM 10m FullProject

zipDEM 3m FullProject

zipSlope 3m FullProject
PRODUCTS

zipDEM 3m PVGB

zipSlope 3m PVGB
PRODUCTS

zipDEM 3m MSCC

zipSlope 3m MSCC
PRODUCTS

zipDEM 3m SLRB

zipSlope 3m SLRB
PRODUCTS

zipDEM 3m NoCo

zipSlope 3m NoCo
Bedrock Geology
(Aquifer Y/N)
INPUT

zipMontereyBedrockGeol

zipSanMateoBedrockGeol

zipSantaCruzBedrockGeol

PRODUCTS

pdfBedrockGeol FullRegion

pdfBedrockGeol Reclass

zipBedrockGeol Reclass GIS
N/A N/A N/A N/A
Soils (Infiltration Capacity) INPUT

zipSoilsMonterey

zipSoilsSanBenito

zipSoilsSanMateo

zipSoilsSantaClara

zipSoilsSantaCruz

zipSSURGO US2003 DB

PRODUCTS

pdfSSURGO Soils

pdfSoil Infiltration

zipSoils FullProject GIS
N/A N/A N/A N/A
Subsurface Input Files   Pajaro Valley Groundwater Basin MSCC - Soquel-Aptos SubBasin SLRB - Santa Margarita SubBasin  
Aquifer Thickness N/A zipPVGB_Thickness GIS zipSAGB_Thickness GIS zipSMGB_Thickness GIS N/A
Aquifer Hydraulic Conductivity N/A zipPVGB_Conductivity GIS zipSAGB_Conductivity GIS zipSMGB_Conductivity GIS N/A
Aquifer Storativity N/A zipPVGB_Storage GIS zipSAGB_Storage GIS zipSMGB_Storage GIS N/A
Vadose Zone Thickness N/A zipPVGB_VadoseThickness GIS zipSAGB_VadoseThickness GIS zipSMGB_VadoseThickness GIS N/A
Water Elevation Change N/A zipPVGB_WaterLevelChange GIS zipSAGB_WaterLevelChange GIS zipSMGB_WaterLevelChange GIS N/A
MAR Suitability SCC + No MC Pajaro Valley Groundwater Basin Mid Santa Cruz County San Lorenzo River Basin North Coast
Surface MAR suitability pdfSurfSuitAllSlopes map

pdfSurfSuitSlopesLess10deg map

zipSurfSuit FullRegion10Deg GIS

zipSurfSuit FullRegionAnySlope GIS

pdfPVGB SurfSuit map

 

zipPVGB SurfaceSuitability GIS

pdfMSCC SurfSuit map

 

zipMSCC_SurfaceSuitability GIS

pdfSLRB SurfSuit map

 

zipSLRB SurfaceSuitability GIS

pdfNoCo SurfSuit map

 

zipNoCo SurfaceSuitability GIS

Subsurface MAR suitability N/A

pdfPVGB SubSurfSuit map

pdfPVGB_Storage

pdfPVGB_Transmissivity

pdfPVGB_VadoseZone

pdfPVGB_WaterLevel


zipPVGB SubSurfSuit GIS

pdfSAGB SubSurfSuit map

pdfSAGB_Storage

pdfSAGB_Transmissivity

pdfSAGB_VadoseZone

pdfSAGB_WaterLevel

 

zipSAGB SubSurfSuit GIS

pdfSMGB SubSurfSuit map

pdfSMGB_Storage

pdfSMGB_Transmissivity

pdfSMGB_VadoseZone

pdfSMGB_WaterLevel

zipSMGB SubSurfSuit GIS

N/A

Combined MAR suitability

(Surface + Subsurface)

N/A

pdfPVGB Composite map

zipPVGB_CompositeSuit GIS

pdfSAGB Composite map

 

zipSAGB 3factors CompositeSuit GIS

 

zipSAGB 6factors CompositeSuit GIS

pdfSMGB Composite map

zipSMGB CompositeSuit GIS

N/A

 

2.      Stormwater Runoff Analysis

 (Table under construction)

 Data  PVGB  MSCC  SLRB
 PRMS output files