Ground Water and Water Ground Water and Water ResourcesResources

OverviewOverview

The supply of water available for useThe supply of water available for useGroundwaterGroundwater

aquifersaquifersexamples of aquifers as resourcesexamples of aquifers as resources

Global distribution of water resourcesGlobal distribution of water resourcesPollutionPollution

Water ResourcesWater Resources

Very little of the earthVery little of the earth’’s water is available in a form directly s water is available in a form directly utilizable by people; that is, as water resources.utilizable by people; that is, as water resources.

Most surface water resources come from surplus (SURPL) Most surface water resources come from surplus (SURPL) utilizationutilization

Groundwater comprises a large percentage of freshwater Groundwater comprises a large percentage of freshwater resourcesresources

GroundwaterGroundwater

Groundwater lies beneath the surface of Groundwater lies beneath the surface of the earth, but is affected by surface the earth, but is affected by surface supplysupplyGroundwater is affected by changes to all Groundwater is affected by changes to all of the earthof the earth’’s spheres due to linkage s spheres due to linkage through the hydrologic cyclethrough the hydrologic cyclePercolationPercolation

Groundwater ConceptsGroundwater ConceptsWater percolates downward through permeable Water percolates downward through permeable rock through the rock through the zone of aerationzone of aeration

rock pores are unsaturated by water, many contain airrock pores are unsaturated by water, many contain air

Water then accumulates in the Water then accumulates in the zone of saturationzone of saturationall rock pores contain waterall rock pores contain water

The The water tablewater table is the upper surface of the zone is the upper surface of the zone of saturationof saturation

its surface follows the contours of the ground aboveits surface follows the contours of the ground abovethe water table controls the movement of surface the water table controls the movement of surface waterwater

PorosityPorositydescribes the size, shape, arrangement, cementation, describes the size, shape, arrangement, cementation, and compaction of subsurface materialand compaction of subsurface material

Permeable/ImpermeablePermeable/ImpermeableWhether or not a subsurface structure permits the flow Whether or not a subsurface structure permits the flow of waterof water

AquiferAquiferA layer of rock that is permeable to water flow in A layer of rock that is permeable to water flow in useable amountsuseable amounts

unconsolidated aquifer: loose sand and gravelunconsolidated aquifer: loose sand and gravelconsolidated aquifer: porous rock, often sandstone or consolidated aquifer: porous rock, often sandstone or limestonelimestone

AquicludeAquicludeA layer of rock that is impermeable to water flow in A layer of rock that is impermeable to water flow in usable amountsusable amounts

Confined AquiferConfined AquiferA layer of permeable rock between two A layer of permeable rock between two impermeable layersimpermeable layersAn aquifer between two An aquifer between two aquicludesaquicludes

Unconfined AquiferUnconfined AquiferAn aquifer without an overlying An aquifer without an overlying aquicludeaquiclude

Perched AquiferPerched Aquiferan aquifer created by a small an aquifer created by a small aquicludeaquiclude at at a higher level than the water tablea higher level than the water table

Intersections of the water table with the Intersections of the water table with the surfacesurface

SpringsSprings: groundwater flows out of the : groundwater flows out of the groundgroundEffluent streamsEffluent streams: supplied by surrounding : supplied by surrounding aquiferaquiferInfluent streamsInfluent streams: supply the local aquifer: supply the local aquifer

Artesian waterArtesian waterWater in confined aquifers are under the pressure Water in confined aquifers are under the pressure of their own weight, creating a pressure level of their own weight, creating a pressure level ((potentiometricpotentiometric surface), beneath this surface, surface), beneath this surface, water flows from the pressure of its weightwater flows from the pressure of its weight

Aquifer recharge areaAquifer recharge areaSurface area where water enters an aquifer to Surface area where water enters an aquifer to recharge it.recharge it.Differ for confined and unconfined aquifersDiffer for confined and unconfined aquifers

DrawdownDrawdownLowering of the water table due to removal of Lowering of the water table due to removal of waterwaterOccurs if rate of pumping or removal exceeds Occurs if rate of pumping or removal exceeds the horizontal flow of water in the aquiferthe horizontal flow of water in the aquifer

Cone of depressionCone of depressionThe shape of the drawn down water table The shape of the drawn down water table surrounding a wellsurrounding a well

Groundwater miningGroundwater miningThe act of removing water from an aquifer The act of removing water from an aquifer at a rate greater than its flow and recharge at a rate greater than its flow and recharge capacitiescapacitiesCollapsing aquifers: water in aquifers Collapsing aquifers: water in aquifers often provide support for the porous rock, often provide support for the porous rock, its removal could result in the rock its removal could result in the rock collapsing, in which case the capacity of collapsing, in which case the capacity of the aquifer is greatly reducedthe aquifer is greatly reduced

Seawater intrusionSeawater intrusionContamination of an aquifer by seawater Contamination of an aquifer by seawater due to overdue to over--pumping the aquiferpumping the aquifer

High Plains AquiferHigh Plains AquiferWorldWorld’’s largest known aquifers largest known aquiferCharged from the Charged from the meltwatersmeltwaters of retreating glaciersof retreating glaciersOnly moderate precipitation todayOnly moderate precipitation todayHeavy groundwater mining over the past 100 Heavy groundwater mining over the past 100 years, the last 50 especiallyyears, the last 50 especially

120,000 wells provide water for 14 million acres 120,000 wells provide water for 14 million acres (170,000 wells in 1978), pumping 26 billion cubic meters (170,000 wells in 1978), pumping 26 billion cubic meters of water per yearof water per yearWater table has dropped 30 meters over last 50 years, Water table has dropped 30 meters over last 50 years, averaging a 2 meter drop per year since 1980.averaging a 2 meter drop per year since 1980.If mining stopped, it would take 1000 years to rechargeIf mining stopped, it would take 1000 years to rechargeWater used to irrigate grain crops (wheat, sorghum and Water used to irrigate grain crops (wheat, sorghum and corn, providing 40% of cattle feed) and cottoncorn, providing 40% of cattle feed) and cotton

Projected: Half of the area (2/3 of Texas portion) Projected: Half of the area (2/3 of Texas portion) destroyed by 2020.destroyed by 2020.

The Middle EastThe Middle East

Groundwater supplies are rapidly being Groundwater supplies are rapidly being depleteddepletedSalt water incursion for tens of kilometers Salt water incursion for tens of kilometers inland in Saudi Arabiainland in Saudi ArabiaSolutions:Solutions:

Desalinization plantsDesalinization plants4000 in the world, 60% in Saudi Arabia4000 in the world, 60% in Saudi Arabia

Pipeline from TurkeyPipeline from Turkey

Global Water ResourcesGlobal Water ResourcesSupply and demand for water are not evenly Supply and demand for water are not evenly distributed over the worlddistributed over the world

Supply is affected by climatic variabilitySupply is affected by climatic variabilityDemand is a product of:Demand is a product of:

population (and growth)population (and growth)level of developmentlevel of development

agriculture relies on precipitation (PRECIP), augmented by agriculture relies on precipitation (PRECIP), augmented by irrigation (SURPL, irrigation (SURPL, ΔΔSTRG)STRG)industry relies more heavily on surplus waterindustry relies more heavily on surplus water

affluenceaffluenceaccessibilityaccessibility

Increased demand for water results in greater Increased demand for water results in greater reliance on the utilization of surface and reliance on the utilization of surface and ground water (SURPL and STRG)ground water (SURPL and STRG)

can cause rivers to run dry (Colorado R., Yellow can cause rivers to run dry (Colorado R., Yellow R.)R.)

PollutionPollutionGroundwater flows at a slower rate than surface Groundwater flows at a slower rate than surface waterwater

Surface water contamination is quickly purged Surface water contamination is quickly purged (elsewhere)(elsewhere)Groundwater contamination is permanent and difficult Groundwater contamination is permanent and difficult to remediateto remediate

Sources: industry, landfills, hazardous and toxic Sources: industry, landfills, hazardous and toxic waste dumps, agriculture (herbicides, pesticides waste dumps, agriculture (herbicides, pesticides and fertilizer), septic tanks and fertilizer), septic tanks

10,000 suspected leaking gas tanks at service stations 10,000 suspected leaking gas tanks at service stations nationwidenationwide

Surface water contamination concentrates Surface water contamination concentrates pollutants downstreampollutants downstream

High cancer rates in New OrleansHigh cancer rates in New OrleansDead Zone in Gulf of MexicoDead Zone in Gulf of Mexico