Fresh Water and Karst Topography

Hydrologic cycle On a global basis: Water from atmosphere to earth (Precipitation) Water from earth to atmosphere (Evaporation and Transpiration) =

Surface Water lakesstreams overland flow Ground water soil pores in rocks regolithsediments

Ground water Water stored beneath the surface, in rock, regolith, soil, sediments Water stored beneath the surface, in rock, regolith, soil, sediments –Flows to surface water –Is recharged (fed) by surface streams

Water percolates downward from soil as gravitational water through aerated zone; reaches water table, which is the top of the saturated zone

aquifer: rock or sediment that holds a body of free-flowing ground water

Ground water utilization: well pumping causes cone of depression;

may cause water table drawdown

Water table and climate

Karst Topography movement of ground water through limestone produces karst landscapes. Characteristics: Sinkholes Sinkholes Caves Caves Springs Springs Lack of surface water Lack of surface water

Requirements: (Not all limestone regions are karst regions)  “pure” limestone –(>80% calcium carbonate) abundant rainfall abundant rainfall complex joint patterns in limestone complex joint patterns in limestone

Carbonation process: 1. carbon dioxide + water carbonic acid 2. carbonic + calciumcalcium acid carbonatebicarbonate acid carbonatebicarbonate in limestone soluble

Soluble product of the reaction is carried away in groundwater Soluble product of the reaction is carried away in groundwater As groundwater seeps through joints, rock is gradually dissolved; beginning of cavern formation As groundwater seeps through joints, rock is gradually dissolved; beginning of cavern formation

Tube passage

As rock dissolves, surface loses underlying support and subsides or collapses: SINKHOLE develops

Travertine Calcite that has precipitated out of groundwater as a mineral deposit carbonation in reverse : calcium calcite + CO 2 + H 2 O bicarbonate travertine

Some types of travertine: soda straws soda straws draperies draperies stalactites stalactites stalagmites stalagmites columns columns