General Groundwater Concepts for GSP Development in Petaluma Valley - PowerPoint PPT Presentation

General Groundwater Concepts for GSP Development in Petaluma Valley Petaluma Valley Groundwater Sustainability Agency Advisory Committee Meeting May 9, 2018 sonomacountygroundwater.org

Presentation Overview 1. Aquifer Properties and Groundwater Movement 2. Groundwater Levels and Surface Water-Groundwater Interaction 3. Groundwater Quality 4. Groundwater Budgets and Models 5. Questions & Discussion sonomacountygroundwater.org

Hydrologic Cycle US Geological Survey Circular 1139 sonomacountygroundwater.org

Aquifer Materials: Porosity and Specific Yield Material Porosity Specific Yield Clay 50% 2% Sand 25% 22% Gravel 20% 19% Modified from Heath, 1983 • Specific Yield = Amount of water that drains from an unconfined aquifer • 20% Specific Yield example: • 1 cubic foot of aquifer material yields 0.2 cubic feet of water • 2 inches of recharge can raise groundwater levels nearly one foot sonomacountygroundwater.org

Aquifer Materials: Hydraulic Conductivity Hydraulic Conductivity : Ability of aquifer materials to transmit water Darcy’s Law of Groundwater Flow (Q) • Hydraulic conductivity (K) • Hydraulic gradient (i) • Cross-sectional area of flow (A) Q = KiA Common methods for estimating Hydraulic Conductivity: • Aquifer Testing (pumping a well and measuring responses in nearby wells) • Aquifer material type (eg, infer from driller’s or geologist’s descriptions from well logs) • Numeric Modeling • Geophysical Surveys sonomacountygroundwater.org

Most Data on Aquifer Properties from Well Logs sonomacountygroundwater.org

Geologic Characterization of Basin sonomacountygroundwater.org

Groundwater Movement Between Recharge and Discharge U.S. Geological Survey Circular 1139 sonomacountygroundwater.org

Unconfined and Confined Aquifers Pumping equal amounts of groundwater from Direct recharge to confined aquifers often limited by unconfined and confined aquifers will result in larger laterally extensive clay layers groundwater-level declines in confined aquifers. Groundwater-level = Groundwater-level = Pressure Head Water Table Harter, UC Division of Ag and Natural Resources, Publication Heath, USGS Water Supply Paper 2220 8083 sonomacountygroundwater.org

Groundwater Levels Change Seasonally and Climatically Well Hydrograph, Groundwater and the Rural Homeowner, U.S. Geological Survey sonomacountygroundwater.org

Groundwater Levels Change When Discharge Exceeds Recharge Groundwater Elevation 20 10 0 -10 -20 -30 -40 1948 1958 1968 1978 1988 1998 Well Hydrograph, Water Well Database, California Department of Water Resources sonomacountygroundwater.org

Groundwater Level Hydrographs and Groundwater Elevation Contour Maps sonomacountygroundwater.org

Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Gaining Stream” “Gaining Stream” Courtesy The Nature Conservancy High Groundwater Levels Groundwater Maintains Stream Flow sonomacountygroundwater.org

Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Losing Stream” “Losing Stream” Courtesy The Nature Conservancy Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater sonomacountygroundwater.org

Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Losing Stream” “Losing Stream” Groundwater Levels Below Stream Channel Courtesy The Nature Conservancy Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater sonomacountygroundwater.org

Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Dry Stream” Dry Stream Seepage to Groundwater Exceeds Stream Flow Dry Stream Channel (Intermittently or Year-round) Pumping Lowers Groundwater Levels Courtesy The Nature Conservancy Stream Loses Flow to Groundwater sonomacountygroundwater.org

Groundwater Quality Contaminant Hydrogeology, C.W. Fetter, 1992 sonomacountygroundwater.org

Petaluma Valley Groundwater Quality Data sonomacountygroundwater.org

Groundwater Budget Inflows Outflows s Natural Land Streambed Well Streambed Groundwater Surface Pumping Discharge E vapotranspiration Surface Percolation Discharge Percolation Inflow Outflow From To Other Adjacent Aquifers Aquifers sonomacountygroundwater.org

Aquifer System and Groundwater Budget Responses to Groundwater Pumping Undeveloped Aquifer System: Natural Recharge = Natural Discharge to surface water, ET, and springs Developed Aquifer System: Sources of water to pumping wells = Some combination of: 1. increased recharge (conversion of gaining to losing streams) 2. reduction/capture of natural discharge to surface water/ET, and 3. removal of stored groundwater • Natural Recharge ≠ Basin Sustainable Yield • Under SGMA Sustainable Yield is set at amount of groundwater that can be pumped without causing an undesirable result. sonomacountygroundwater.org

Groundwater Flow Model Integrated Hydrologic Model • Climatically driven agricultural demands • Streamflow simulation • Incorporation of surface water diversions • Recycled Water deliveries • Representation of land use trends and changes Example Model Uses • Estimate hydrologic budget • Identify recharge areas • Evaluate water-resource management strategies • Evaluate climate-change impacts • Evaluate effects of changes in land- use sonomacountygroundwater.org

SGMA Undesirable Results (1) Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon. (2) Significant and unreasonable reduction of groundwater storage. (3) Significant and unreasonable seawater intrusion. (4) Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies. (5) Significant and unreasonable land subsidence that substantially interferes with surface land uses. (6) Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water. sonomacountygroundwater.org

Questions and Discussion http://www.sonomacountygroundwater.org sonomacountygroundwater.org