Lab 12: Groundwater

Objectives:

- Porosity

- Permeability

- Be able to identify and describe…

- Water table

- Potentiometric surface

- Zones of recharge & discharge

- Groundwater/unconfined & confined aquifers

- Aquifer / aquitard

- artesian wells

- cone of depression

Introduction:

Groundwater: water within fully saturated bedrock or unconsolidated sediment

Water table: to top surface of groundwater

Porosity: volume of void space in sediment or bedrock - higher porosity = more voids

Permeability: ease of water flow through a rock - permeable v. impermeable

Aquifers: permeable bedrock that conducts water (sandstones, unconsolidated sediments,

limestones)

Confining beds: impermeable bedrock that prevent the flow of water (clay, mudstone,

shale, igneous and metamorphic rocks)

Caves and Karst:

Karst: dissolution of underlying soluble rock (limestone)

Figure 12.2 - Sinkholes, solution valleys, springs, disappearing streams, caves

Water saturated in calcite may precipitate crystals - stalactites, stalagmites

Groundwater Withdrawal: Figure 12.10

Well: hole dug into the ground

Unconfined beds: no aquitard above, water not under pressure

Confined: aquitard above and below permeable unit - water may be under pressure

Potentiometric surface: water-pressure surface

Artesian wells: when the top of the well is below the water-pressure surface

Recharging: replenishing the aquifer from rainfall, snowmelt or rising groundwater

Figure 12.9 - Cone of depression: downdrawal of water around well