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
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US Geological Survey Circular 1139
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Material Porosity Specific Yield Clay 50% 2% Sand 25% 22% Gravel 20% 19%
Modified from Heath, 1983
drains from an unconfined aquifer
yields 0.2 cubic feet of water
groundwater levels nearly one foot
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Hydraulic Conductivity: Ability of aquifer materials to transmit water Darcy’s Law of Groundwater Flow (Q)
Q = KiA Common methods for estimating Hydraulic Conductivity:
responses in nearby wells)
geologist’s descriptions from well logs)
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U.S. Geological Survey Circular 1139
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Direct recharge to confined aquifers often limited by laterally extensive clay layers Pumping equal amounts of groundwater from unconfined and confined aquifers will result in larger groundwater-level declines in confined aquifers.
Harter, UC Division of Ag and Natural Resources, Publication 8083 Heath, USGS Water Supply Paper 2220
Groundwater-level = Water Table Groundwater-level = Pressure Head
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Well Hydrograph, Groundwater and the Rural Homeowner, U.S. Geological Survey
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Well Hydrograph, Water Well Database, California Department of Water Resources
10 20 1948 1958 1968 1978 1988 1998 Groundwater Elevation
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“Gaining Stream”
Courtesy The Nature Conservancy
High Groundwater Levels Groundwater Maintains Stream Flow
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“Losing Stream”
Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater
Courtesy The Nature Conservancy
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“Losing Stream”
Groundwater Levels Below Stream Channel Pumping Lowers Groundwater Levels Stream Loses Flow to Groundwater
Courtesy The Nature Conservancy
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Dry Stream
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
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Contaminant Hydrogeology, C.W. Fetter, 1992
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Natural Land Surface Percolation Streambed Percolation
Inflow From Adjacent Aquifers
Well Pumping Streambed Discharge Groundwater Evapotranspiration Surface Discharge
Outflow To Other Aquifers
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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:
gaining to losing streams)
discharge to surface water/ET, and
groundwater that can be pumped without causing an undesirable result.
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Integrated Hydrologic Model
demands
diversions
and changes Example Model Uses
management strategies
use
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(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.
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