Anthony Cuzzola Planet Earth Exam 4 review A Hidden Reserve Groundwater Streams Floods Running Water Restless Realm Oceans and Coasts Amazing Ice Glaciers and Ice Ages Global Change The C Cycle Hydrolic cycle earths water balance powered by the sun Distribution of H2O Oceans 96 Glaciers 3 groundwater 1 Surface water rivers lakes 1 atmosphere 001 biosphere 0001 CLICKER of H2O in earths surface what is potable A 1 Why is groundwater such a valuable resource Abundant 70 times more fresh water below ground than above it constant ground water is available even during dry periods widespread can flow from different areas humid environments where it is needed in dry regions Porosity and permeability Porosity of material that consists of open spaces Compactions and cementation reduces porosity Permeability a measure of how easily a solid allows fluid to pass through it a high porosity does not necessarily mean a corresponding high permeability clay exp of high porosity and low permeability Recharge place where ground water is replenished Discharge where groundwater flows from the surface Recharge area area where precipitation reaches the saturated zone Discharge area where subsurface water is discharged to streams or to lakes ponds or swamps Watertable outcrops at the surface of streams lakes Changes in rainfall affect elevation of the watertable CLICKER the water table must be flatlying True False A False it never is Topography of the watertable Water table mimics surface topography but is smoother Why doesn t it assume a level surface 1 Capillary action and surface tension 2 Water infiltrates down to h1 and h2 faster than it flows from h1 to h2 How fast does groundwater flow laterally depends on 2 things slope of the water table steeper faster permeability higher faster Rates of groundwater movement slow to very slow Typically 10 100 cm day 40 400 m year Aquifer sediment rock through which water flows easily Aquitard sediment rock that restricts water flow Confining bed blocks flow completely Unconfined aquifer intersects surface Confined aquifer bracketed by aquitards Perched water table Springs have lots of causes Standard Discharge Perched discharge Impermeable base permeable layer connected fractures aquaclude at surface Artesian flow up a joint Confined aquifer creates artesian wall artesian means hydraulic gradient is large enough to cause groundwater to flow upwards and out of the ground Municipal water systems Well water pumped to holding tank Gravity maintains pressure from there to faucet Most of our drinking water comes from wells Wells dug or drilled through saturated zones Water is then pumped or lifted out Water removed faster than recharge lowers the water table Water table can drop below usable depth through excessive use Long term effect of over pumping ground water extraction leads to pore collapse and ground subsidence CLICKER what is going on in this picture Groundwater over pumping many places being removed so fast that the ground beneath is actually shrinking Saltwater intrusions extensive pumping causes saltwater intrusion into freshwater pipes Chemistry of Groundwater Groundwater is not pure contains dissolved minerals ions ability to carry ions a function of temp pressure until max possible ions are reached water is undersaturated thereafter it is saturated if either temp or pressure decrease saturated becomes oversaturated Groundwater passing through Salt will be too salty for much use Limestone will be hard water counteracting soap lather precipitate white scale standing water Iron rich rocks will leave orange stain Caves will only form in carbonate material limestone or dolomite Karst Topography is a landscape in which caves and sinkholes are so numerous that they form a peculiar topography characterized by many small closed basisn disrupted drainage pattern streams disappearing into the ground streams reappearing as large springs all this shit only where carbonate occurs Rock types on which karst develops limestone dominant mineral is calcite CaCO3 dissolves readily in weakly acidic water dolomite dolomite is the dominant mineral Karst Landforms humid temperature climates blind valley a valley that ends abruptly where stream vanishes underground sinking stream stream that vanishes underground usually at terminus of blind resurgence point where waters from sinking stream reemerges from dry valley valley that no longer exhibits channelized flow cave a natural underground room or series of rooms large enough to be entered valley underground by a person Major features of Karst topography streams floods geology of running water landscape of planet or moon w o water never changes Earths moon 3 9 billion years old Sheetwash thin covers surface just flows on surface rare Downcuts evolution beginning of strea sheetwash becomes concentrated erodes scours out a channel Headward erosion fastest downcutting at a channel head channel moves upslope upstream Tributaries from to feed new stream drainage network develops Solid rock narrow cannon Unstable walls broad valley this shit might not be important Hard soft rock stairstep valley Streams are surface expression of groundwater Monitoring wells tell us water levels When water table is saturated and cant hold anymore water streams over flow Types of drainage patterns dendritic looks like tree branch treelike drainage pattern dendro means tree 1 dendrite like veins of a leaf 2 flow over uniform surface most common type of stream development radial flow from center point of mtn or volcaneo Resemble wheel spoke rectangular controlled by grid of fractures as joints or faults Right angle joints trellis form in long valleys Trunk stream cuts resistant ridges water gaps Delaware water gap How does drainage basins decide where to put water drainage divide on topographical high water can flow 1 of 2 ways this is the catchment region Base level decrease sea level drop uplift at mouth uplift at stream head draining of lakes Base level increase sea level rise subsidence at stream mouth subsidence at head creation of lakes Niagra falls exp of change in base level Tectonic uplift and changing sea level can significantly change base level 4 kinds of erosions due to running water scouring removing loose fragments breaking lifting snapping off fragments lifting fragments off bed abrasion grinding action of sand in water column dissolution dissolving more soluble minerals Severity of erosion depends on water velocity stream gradient water