1. Groundwater Fundamentals
Module 9.1

2. 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

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: 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

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), and dht/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. 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

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
Unconfined Aquifer
Recharge Zone
Confined Aquifer
landfill
Municipal well field
Piezometric surface
Gravel
Clay
flow
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 and Losing Streams
Gaining stream
Effluent stream
Losing stream
Influent stream
Perched losing stream
Flow-through stream
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
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.

21. 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