chapter 17 groundwater. figure 17.2 variations in the water table water tends to mimic the land...

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