Movement of water can change position of water table Springs Form where aquifers with an aquiclude beneath them encounter ground surface Local aquicludes => perched water table & aquifers Well water Wells are drilled into aquifers Water rises to the level of local water table and must be pumped to surface Cone of depression (drawdown) Local water table lowered by pumping out water faster than it can flow back in Drawdown can cause other wells to go dry and the ground to sink Artesian Systems Confined aquifer => aquicludes above and below Recharge at higher elevations causes pressure Pressure released by well => artesian well Groundwater-Rock Interaction Dissolution: water chemically reacting with rock Pure water will disolve some materials (salts, gypsum) Rainwater slightly acidic (atmosphere's CO 2 dissolved in water) Other natural acids form from CO2 produced by organisms in soil Acids dissolve limestone (solid calcite + acid => calcium and bicarbonate ions in water) Loss of CO 2 from water causes calcite to precipitate, forming travertine Karst Topography Formation promoted by: High rainfall Abundant vegetation (provides CO 2 -rich waters) Extensively jointed limestone formations Appreciable hydraulic gradients Landscapes controlled by disolution of limestone bedrock Disappearing surface streams (drain into caves) Limestone pillars produced by preferential dissolution along joints, etc. Sinkholes Form by sagging of the soil as limestone beneath it is dissolved making a hollow Or complete collapse of the roof of an underlying cave making a steep hole Sinkholes can merge to produce a solution valley Florida karst Caves & Caverns Solution features later modified by precipitation (stalacite, stalagmite, etc.) Most cave formation occurs below the water table as water dissolves limstone Preferential dissolution along joints/fractures => linear cave systems A lowering of water table results in dry caves Dry caves can be ornamented by infiltrating waters: CO 2 and ion-charged waters percolating downward ecounter air of caves and lose CO 2 , precipitating travertine (calcite) Features include: dripstone, flowstone, stalactites, stalagtites, and columns Surface Precipitation Features Precipitation of travertine also occurs at surface Spring waters lose CO 2 due to aggitation, temperature changes, or the activity of organisms Features include: rimstone pools, waterfalls, tufa towers (Mono Lake) Modification of Groundwater Systems Most changes in groundwater systems due to excessive pumping Water withdrawn faster than recharge: High Plains Aquifer (central US) Pumping up to 100x greater than recharge Water table lowered;
(Appreciable hydraulic gradients Landscapes; controlled; by disolution of limestone bedrock Disappearing surface streams (drain into caves) Limestone pillars produced by preferential dissolution along joints, etc. Sinkholes Form) (water; chemically reacting; with rock Pure water) (dissolve limestone (solid calcite + acid => calcium and bicarbonate ions in water) Loss of CO 2 from water; causes; calcite) (aquifers with an aquiclude beneath them; encounter; ground surface; L:water table Springs Form) (Local water table; lowered; ) (a steep hole; can merge; to produce a solution valley) (Water rises to the level of local water table and must be pumped to surface Cone of depression; can cause; other wells to go dry) Context(Water rises to the level of local water table and must be pumped to surface Cone of depression can cause,List([231, 434))):(other wells; to go; dry) (pressure Pressure; released; by well =>) (Sinkholes; to produce; a solution valley) (travertine Karst Topography Formation; promoted; by) (Limestone pillars; produced; by preferential dissolution along joints, etc.) (the ground to sink Artesian Systems Confined aquifer => aquicludes above and below Recharge at higher elevations; causes; pressure Pressure released by well =>) (Dry caves; can be ornamented; ) (water Wells; are drilled; into aquifers) (High Plains Aquifer; Pumping up; to 100x greater than recharge Water table) (CO2; produced; by organisms in soil Acids) (atmosphere's; dissolved; L:in water) (Dry caves; by infiltrating; waters) (it; can flow; back in Drawdown) (Caves & Caverns Solution features; modified; by precipitation; T:later)
Water rises to the level of local water table and must be pumped to surface Cone of depression can cause,List([231, 434))
Appreciable hydraulic gradients Landscapes water dissolve limestone (solid calcite + acid => calcium and bicarbonate ions in water) Loss of CO 2 from water aquifers with an aquiclude beneath them Local water table a steep hole Water rises to the level of local water table and must be pumped to surface Cone of depression other wells pressure Pressure Sinkholes travertine Karst Topography Formation Limestone pillars the ground to sink Artesian Systems Confined aquifer => aquicludes above and below Recharge at higher elevations Dry caves water Wells High Plains Aquifer CO2 atmosphere's Dry caves it Caves & Caverns Solution features
controlled chemically reacting causes encounter lowered can merge can cause to go released to produce promoted produced causes can be ornamented are drilled Pumping up produced dissolved by infiltrating can flow modified
by disolution of limestone bedrock Disappearing surface streams (drain into caves) Limestone pillars produced by preferential dissolution along joints, etc. Sinkholes Form
with rock Pure water
calcite
ground surface L:water table Springs Form
to produce a solution valley
other wells to go dry
dry
by well =>
a solution valley
by
by preferential dissolution along joints, etc.
pressure Pressure released by well =>
into aquifers
to 100x greater than recharge Water table
by organisms in soil Acids
L:in water
waters
back in Drawdown
by precipitation T:later