Landform Geography Groundwater and Karst Landscapes

Movement & Storage of Groundwater Precipitation sinks into soil’s soil-water belt In dry soil, water is held tight by sediment grains as hygroscopic water – unavailable for plants When pore spaces within soil full of water, soil at Field Capacity – additional water flows down into unsaturated zone Water collects above an impermeable aquiclude to form saturated zone Large saturated zone is aquifer

Fate of Precipitation on Soil

Soil-Water Conditions

Saturated Zones & Aquicludes

High Plains (Ogallala) Aquifer Underlies much of Great Plains from TX to SD Water deposited in Ice Ages 1.6 M- 10K yrs ago

Heavy usage, esp. center-pivot irrigation Drawdown significant in parts of aquifer High Plains (Ogallala) Aquifer Center-Pivot Irrigation Drawdown

Artesian Wells and Springs Natural pressure brings water to surface in artesian well

Patterns of Groundwater Depletion Cone of Depression – cone-shaped depression in water table that occurs around a well

Subsidence Settling or sinking of a surface due to removal of water or sediment from below Worst around large cities such as Venice, Italy and agricultural regions such as the San Joaquin Valley of California

Groundwater Contamination Dumped chemicals can be carried by moving groundwater to sources of drinking water Recent federal rules have reduced uncontrolled dumping and contamination

Karst Landforms Caves, sinkholes and other soluble rock features Form in extensive, thick deposits of limestone Limestone 80%+ calcium carbonate – dissolves easily through carbonation

Caves and Caverns Caves – underground voids in rock big enough for people to enter Cavern – large cave system Form just below water table in limestone – when water table falls, empty caverns are exposed

Karst Topography - Sinkholes Most common surface feature of karst is sinkhole Sinkhole – depression in regions of cavernous limestone – forms from collapse of cave Often found with disappearing streams that enter underground channels Some sinkholes fill with water, forming ponds Sinkholes can be hazards, collapsing under homes or roads

Sinkhole Landscape