GEOL 113 Lab: Ground water

August 29, 2003

Infiltration = Precipitation – [runoff + evaporation + transpiration]

A. Water Table (p. 199) – a depth below ground below which all void spaces are filled with water.

1. Recharge Area – area where confined aquifers are exposed to receive infiltrating water.

B. Porosity vs. Permeability (p. 199-200)

1. The total volume of pore space in a rock or soil is termed porosity.

a. Primary Porosity – initial spaces between grains, controlled by shape, size, and degree of sorting.

b. Secondary Porosity – porosity that develops as the result of fracturing of the rock near the earth’s surface.

2. The degree to which the pores are interconnected is permeability.

3. Darcy’s Law – Flow velocity or seepage velocity. Describes hydraulic conductivity.

C. Aquifers

1. Unconfined – an aquifer that allows unrestricted, three-dimensional flow of ground water.

2. Confined – an aquifer that is interlayered with less porous and permeable layers and does not allow unrestricted, three-dimensional flow.

D. Well Terms

1. Gradient

a. Groundwater contour lines

b. Flow lines

2. Artesian Well – well in which the pressure of the overburden causes water to rise in the well above the GWT.

3. Flowing artesian well – well in which the pressure of the overburden causes the water in the well to rise and flow onto the land surface.

4. Drawdown – The amount the water surface drops around a well.

5. Cone of Depression – Area around a well formed from drawdown of the water table.

6. Hard Water – ground water that contains an abundance of dissolved calcite and bicarbonate ions.

7. Saltwater Incursion/Encroachment – Excessive pumping of ground water in coastal areas.

8. Contamination

9. Fluids with different density

E. Subsidence – lowering of the ground surface due to excess pumping of water, oil, etc. This causes grains to collapse together and lower the surround ground surface.

F. Karst Topography (p. 200)– Terrains are pitted with sinkholes and solution valleys. Only major streams flow in well-defined valleys and tributaries may disappear.

Equations on page 200. (Fig. 12.1)