Groundwater Fundamentals Module 9.1

Groundwater NOTE: Storage Reservoirs and Fluxes Interflow + Surface Runoff When we talk about management, we are concerned with the alteration to flows and storage reservoirs… Source: Wisler & Brater, 1949, Hydrology

Groundwater Flow… …Produces Baseflow

Groundwater as a “slow” reservoir

Groundwater Terminology

Confined and Unconfined Aquifers

Artesian Well

More on Aquifer Types…

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

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), and dht/dx is the gradient of pressure, or head

Hydraulic Conductivity (kv) Hornberger, 1998

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

Groundwater Development

Groundwater/Surface Water Connections Gaining Stream In systems with high degree of groundwater/surface water connectivity (highly transmissive sediments) Pumping Well Implications: Quality implications – contaminant transfer Stream temperature Quantity implications: Groundwater pumping will “pull” water from surface Groundwater pumping less regulated than surface water Note:: this is why important to understand flow processes in systems Manage groundwater as surface water (conjunctive use) Examples: Snake River Plain, Deschutes in Oregon Ex:: Sea water intrusion Cone of Depression Groundwater

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

Recharge Zone Protection Example Unconfined Aquifer Recharge Zone Confined Aquifer landfill Municipal well field Piezometric surface Gravel Clay flow Clay

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

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

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

2nd-Order / Unconstrained reach of WS03, HJA View of WS01 study site with water table contours (equipotentials) and some hand sketched flow paths See dominance of steps created by wood or boulders Scale (m) 25 50 Kasahara & Wondzell (2003) Water Resour. Res.

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