Chapter 10 Groundwater What you NEED to Know

The Hydrosphere 97% of water is in the.001% is in the.0091% is in 2% is in.3% is

Precipitation & Groundwater Precipitation - Runoff - Interception - Evaporation

Groundwater Storage Porosity – amount of Well sorted sediments have more pore space than poorly sorted sediments

Zone of Saturation Depth under the Upper boundary of the ZOS is called the

Zone of Saturation - continued Water in Zone of Saturation is called Above the water table is

Zone of Saturation - continued Gravitational water – water pulled down by gravity to water table Capillary water – water drawn up from water table by

Groundwater Movement Ability of material to allow water to move through is called Permeability is directly related to pore size (bigger pores, higher permeability)

Groundwater flows in the direction of slope of the water table. Flow velocity Groundwater Movement – cont.

Groundwater flows through permeable layers, called aquafers. (ex. Sand, gravel) Impermeable layers are called (ex. Clay, silt) Groundwater Movement – cont.

10.2 Groundwater Erosion & Deposition

Dissolution by Groundwater Most groundwater contains carbonic acid CO 2 + H 2 O H 2 CO 3 H 2 CO 3 H + + HCO 3 -

Hydrogen ions react with calcium carbonate & dissolve it. CaCO 3 + H + Ca 2+ + HCO 3 - Calcium carbonate then precipitates out elsewhere, and CO 2 & H 2 O are released. Dissolution by Groundwater

Caves Form when groundwater Limestone is also deposited as

Karst Topography Groundwater erodes Caves can collapse, forming Sinks are places where streams (called sinking streams) drain into underground cave systems

Groundwater Deposits Hard water has high amounts of dissolved calcium, magnesium and / or iron. Hard water can leave deposits in –Pipes –Caves stalactites & stalagmites

10.3 Groundwater Systems

Springs Where an aquifer and an aquiclude come into contact with the surface, water is discharged, in a

Aquiclude Aquifer Spring

Hot Springs & Geysers Where aquifers descend deep into Earth’s crust, or where they are heated by recent igneous activity, hot springs & geysers result.

Wells Wells are holes dug to reach groundwater. Drawdown: wells lower the water table around them.

Wells - continued Recharge: precipitation adds water back into the zone of saturation.

Confined Aquifers

Artesian Wells & Springs In confined aquifers, the recharge area is generally at higher elevation than the rest of the aquifer. Discharge areas (wells & springs) are therefore under pressure

Threats to Groundwater

Sources of Pollution