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Groundwater Fundamentals

Understand groundwater fundamentals, aquifer terminology, Darcy's Law for flow calculations, hydraulic conductivity, groundwater development, sources, and connections. Learn about the impact of extraction on subsidence and surface water quality.

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Groundwater Fundamentals

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  1. Groundwater Fundamentals Module 9.1

  2. Groundwater Source: Wisler & Brater, 1949, Hydrology

  3. Groundwater Flow… …Produces Baseflow

  4. Groundwater as a “slow” reservoir

  5. Groundwater Terminology

  6. Confined and Unconfined Aquifers

  7. Artesian Well

  8. More on Aquifer Types…

  9. Hydraulic Head Pressure: Where:r = density of water (kg m-3)g = gravitational acceleration (m s-2)hp = pressure head hp ht a Total hydraulic head (ht): z datum Where:z = elevationhp = pressure head

  10. Darcy’s Law Darcy’s Law defines groundwater flow: where:Q is discharge (L3 T-1)kv is the hydraulic conductivity (L T-1)A is area of flow (L2), anddht/dx is the gradient of pressure, or head

  11. Hydraulic Conductivity (kv) Hornberger, 1998

  12. Example 800 m 85 m 2 m kh=5 m day-1 Fine sand 25 m

  13. Groundwater Development

  14. Gaining Stream Groundwater/Surface Water Connections In systems with high degree of groundwater/surface water connectivity(highly transmissive sediments) Pumping Well Cone ofDepression Groundwater

  15. Subsidence Causes:Fluid withdrawal Sinkholes Drainage of Organic soils Mining From USGS Professional Paper 1401-A, "Ground water in the Central Valley, California- A summary report"Photo by Dick Ireland, USGS, 1977

  16. Recharge Zone Protection Example UnconfinedAquifer Recharge Zone Confined Aquifer landfill Municipal well field Piezometric surface Gravel flow Clay Clay

  17. Groundwater Development • Multiple pumping wells can cause interference between cones of depression • Extraction should not exceed recharge • Water mining • Extraction may cause subsidence • Recharge zones should be protected • Ensure adequate water flow • Ensure quality • Extraction may affect surface water • Many watershed management actions are taken to protect quality

  18. Gaining stream Effluent stream Losing stream Influent stream Perched losing stream Flow-through stream Gaining and Losing Streams Dingman

  19. Hyporheic Zone • Zone where water is exchanged between surface and groundwater • Controlled by geomorphology (upwelling and downwelling) • Biochemical processing: water quality & habitat issues • Temperature

  20. 2nd-Order / Unconstrained reach of WS03, HJA Scale (m) 0 25 50 Kasahara & Wondzell (2003) Water Resour. Res.

  21. Proposed C & D Landfill Example Creek Modeled contaminant plumes Zone exceedingMCL’s for drinking water Old Gravel Pit Constituents of ConcernSulfate Arsenic Chromium Iron 1,2-DCA Total Dissolved Solids Increased, butMCL’s for drinking Water not exceeded Glacial Outwash Domestic Wells Flow Direction Municipal Wells

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