Types of AquifersTypes of Aquifers

ConfinedConfined aquifer aquifer overlain by less overlain by less permeable permeable materialsmaterials

UnconfinedUnconfined aquifer aquifer open to Earth’s open to Earth’s surface and to surface and to infiltrationinfiltration

PerchedPerched aquifer underlain aquifer underlain by low-permeability unitby low-permeability unit

ArtesianArtesian aquifer: water rises aquifer: water rises in pipe (maybe to surface)in pipe (maybe to surface)

17.04.c,d.mtb

How Does Water Move How Does Water Move Between the Surface and Between the Surface and

Subsurface?Subsurface?

Water table generally Water table generally below surface, so below surface, so water can seep inwater can seep in

Water can soak into Water can soak into subsurface and become subsurface and become

groundwatergroundwater

Where water table intersects Where water table intersects surface, water can flow outsurface, water can flow out

17.05.a1

How Are Lakes How Are Lakes and Wetlands and Wetlands

Related to Related to Groundwater?Groundwater?

Observe the settings of Observe the settings of lakes compared to the lakes compared to the water tablewater table

Water table Water table intersects surfaceintersects surface

Perched above Perched above water tablewater table

Wetlands at Wetlands at water table or water table or perched perched

On topographic benchOn topographic bench Valley bottomValley bottom

17.05.c1

How Do Streams How Do Streams Interact with Interact with

Water Table?Water Table?

Observe how each Observe how each stream relates to stream relates to water table and flow water table and flow of groundwaterof groundwater

Stream higher Stream higher than water table: than water table: loses waterloses water

Stream lower than water Stream lower than water table: gains water table: gains water

Mound of groundwater below stream Mound of groundwater below stream from water flowing into subsurfacefrom water flowing into subsurface

17.05.d

How Do Caves Form?

Groundwater dissolves material

Most in limestone (soluble)

Features widen to cavities and caves

Above water table, cave may be dry

Below water table water further dissolves material

17.06.a1

What Features Accompany What Features Accompany Caves?Caves?

Dripping water evaporates, precipitates calcite

Roof collapse can form sinkhole on surface

Cave formations on roof, floor, and walls

Surface with sinkholes, limestone pillars, disappearing streams = karst topography

17.06.c1

How Do We Study How Do We Study Groundwater?Groundwater?

Geophysical Geophysical surveys: depth to surveys: depth to bedrock and waterbedrock and water

Field studies: Field studies: sequence and sequence and character of character of rocksrocks

Drilling: verify geology, depth to water Drilling: verify geology, depth to water table, provide samples, pump teststable, provide samples, pump tests

Measure discharge, Measure discharge, losses/gains, and losses/gains, and

water qualitywater quality

17.07.a1

How Do We Depict the How Do We Depict the Water Table?Water Table?

Contour: Contour: water table water table at same at same elevation; elevation; blue arrows blue arrows show flowshow flow

Numbers Numbers show show elevations elevations of the water of the water table: table: what what is the is the pattern?pattern?

Compare water table Compare water table to other featuresto other features

17.07.b

Effects of Overpumping Effects of Overpumping GroundwaterGroundwater

After pumping: After pumping: cone of cone of depressiondepression

Before Before overpumpingoverpumping

17.08.a

Other Problems of Other Problems of OverpumpingOverpumping

Along coast: Along coast: freshwater floats freshwater floats on saltwater, so on saltwater, so draw in saltwaterdraw in saltwater

Water table drops, aquifer Water table drops, aquifer compacts, land subsidencecompacts, land subsidence Earth fissuresEarth fissures

17.08.b,c

How Can Water How Can Water Become Become

Contaminated?Contaminated?

Identify possible sources of surface water and groundwater contamination

LandfillLandfill

Mining and naturally Mining and naturally mineralized rockmineralized rock

Septic Septic tanktank

FarmFarm

Leaking Leaking tank in gas tank in gas stationstation

Truck Truck fuel fuel spillspill

Dry Dry cleanercleaner

Brought Brought by riverby river

Factory wells, Factory wells, spills, emissionsspills, emissions

Fuel Fuel storage storage tankstanks

Brought from outside area by groundwater

HouseholdsHouseholds

17.09.a1

How Does How Does Groundwater Groundwater

Contamination Contamination Move?Move?

Can be Can be filtered if filtered if flows flows slowly, slowly, like like through through sandssands

With groundwater With groundwater down water tabledown water table

Not filtered if flows Not filtered if flows rapidly, like in rapidly, like in

limestone limestone cavescaves

17.10.a

How Do We Track and How Do We Track and Remediate Groundwater Remediate Groundwater

Contamination?Contamination?

Contour water Contour water table table

and and contaminationcontamination

Drill wells to intercept plume, Drill wells to intercept plume, pump and treat waterpump and treat water

Spreads out due to diffusion Spreads out due to diffusion and mixing, forming and mixing, forming contamination plumecontamination plume

17.10.c

Setting of the Ogallala Setting of the Ogallala AquiferAquifer

Unconfined aquifer; water levels Unconfined aquifer; water levels dropping in south; some parts dropping in south; some parts may run dry (graphs below)may run dry (graphs below)

17.11.a

Ogallala Water Supplies and Ogallala Water Supplies and UsageUsage

Thickest in northThickest in north More rain in eastMore rain in east Water table decline Water table decline greatest in south greatest in south (Kansas & Texas)(Kansas & Texas)

17.11.b-c

17.12.a1

Investigation: Who Polluted Investigation: Who Polluted Water in This Place?Water in This Place?

17.12.a2

Investigation Data TableInvestigation Data Table