Groundwater Chapter 10 Notes

Hydrosphere Oceans (97%) Polar ice caps/glaciers (2.15%) Groundwater (0.31%) Lakes (0.009%) Atmosphere (0.001%) Rivers and streams (0.0001%)

Groundwater All water on land comes from the ocean, through evaporation and precipitation. Infiltration: precipitation that trickles into the ground to become groundwater

Porosity Water is stored in pore spaces in the ground The percentage of pore spaces in a rock or sediment is the porosity Can vary from 2% to 50%

Zone of Saturation

Zones of Aeration and Saturation

Permeability The ability of water to move through sediment and rock is called permeability Aquifers are permeable rock layers that allow groundwater to flow through them A layer that is impermeable to ground water is an aquiclude

Aquifer

Springs Emergence of springs Hot springs/geysers Groundwater emerges wherever the water table intersects Earth’s surface Springs tend to form where an aquifer and an aquiclude are in contact Most often occur on a slope or hillside

Cave Formation A cave is a natural underground opening with a connection to the surface Most caves form in limestone bedrock when limestone is dissolved by groundwater: CO2 + H2O  H2CO3 Carbonic acid reacts with limestone to produce soluble ions

Karst

Groundwater Deposits Calcite in ground water precipitates to form new mineral deposits (stalactites, stalagmites, etc.)

Wells Wells are used to draw water out of an aquifer Overpumping lowers the water table and creates a cone of depression

Artesian Wells Artesian wells produce water under pressure due to recharge at a higher elevation

Threats to our Water Supply Overuse: groundwater supplies can be depleted if pumped faster than the recharge rate (Ogallala Aquifer) Subsidence: sinking of ground elevation when water table drops Pollution (next slide)

Pollution Chemicals, sewage, salt, radon