General Groundwater Concepts for GSP Development in Sonoma Valley Sonoma Valley Groundwater Sustainability Agency Advisory Committee Meeting May 8, 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
Sonoma Valley Hydrogeologic Setting Complex Geology: • Intermixed sedimentary and volcanic deposits • Layers have been uplifted, tilted and faulted Sonoma Valley Groundwater 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
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Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Gaining Stream” “Gaining Stream” High Groundwater Levels Groundwater Maintains Stream Flow Courtesy The Nature Conservancy sonomacountygroundwater.org
Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Losing Stream” “Losing Stream” Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater Courtesy The Nature Conservancy sonomacountygroundwater.org
Groundwater – Surface Water Connection Groundwater Affects Stream Flow “Losing Stream” “Losing Stream” Groundwater Levels Below Stream Channel Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater Courtesy The Nature Conservancy 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) Seepage to Groundwater Exceeds Stream Flow Dry Stream Channel (Intermittently or Year-round) Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater Courtesy The Nature Conservancy sonomacountygroundwater.org
Sonoma Valley: Seepage Runs May 2010 Discharge Segments (Groundwater flows into Stream) • Most of Sonoma Creek • Most of Calabazas • Lower reaches of Fryer and Nathanson Recharge Segments (Stream recharges Groundwater) • Sonoma Creek near Kenwood • Carriger • Upper reaches of Fryer and Nathanson • Portion of Felder Creek Paired Gauge Location sonomacountygroundwater.org
Paired Stream/Groundwater Monitoring Location sonomacountygroundwater.org
Groundwater Quality Contaminant Hydrogeology, C.W. Fetter, 1992 sonomacountygroundwater.org
Salinity In Groundwater is a Concern Salinity Sources: • Historical Brackish Water Beneath Tidal Marshlands • Thermal Water • Deep Groundwater from Older Formations 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 son omacountygroundwater.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 • Improved streamflow simulation • Incorporation of surface water diversions • Recycled Water deliveries • Representation of land use trends and changes • Uncertainty analysis to better understand and convey applicability and limitations of the model 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
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