Chapter 17 Groundwater

Figure 17.2

Variations in the Water Table

Water tends to mimic the land surface

Variations in rainfall & permeability

Gainingand

Losing StreamsFigure 17.4

Groundwater Storage

Porosity% of pore spacesFluid Storage

Table 17.2

Groundwater Movement

Permeabilityability to transmit a fluid

Aquifer

Yields significant quantities of water

High porosity & permeability

Aquifers

Confined/Closed

Unconfined/Open

Long Island Aquifers

Upper Glacial

Magothy

Lloyd

Aquiclude

Inhibits movement of groundwater Impermeable

Clay or Solid Bedrock

Groundwater Movement

Darcy’s Law

Q=K(dh/dl)A

Darcy’s Law

Q=Discharge

K=Hydraulic Conductivity

dh=Change in water table elevation

dl=Distance over which change occurs

A=Area in question

Spring Resulting from a Perched Water Table

Figure 17.8

Figure 17.13

Artesian Well

Figure 17.15

Artesian Pressure System

Excess Groundwater Withdrawal

Subsidence – land surface sinks

• California

• Venice

• Texas

Excess Groundwater Withdrawal

Saltwater Contamination• Excess groundwater withdrawal

• Saltwater is drawn into wells

• Coastal areas

• Ghyben-Herzberg Equation

Ghyben-Herzberg Equation

Total thickness of freshwater lens = x + 40x

Saltwater Contamination

Figure 17.19

Groundwater Contamination

Sewage

• Extremely permeable aquifers (gravel)

• Travels long distances without being filtered

Groundwater & Erosion

Caves

Caverns

Sinkholes

End of Chapter 17