GROUNDWATERGROUNDWATER

GROUNDWATERGROUNDWATER

Groundwater is subsurface water that fully Groundwater is subsurface water that fully saturate pore spaces of bedrocksaturate pore spaces of bedrock

The rate of movement of groundwater is The rate of movement of groundwater is gravity driven, varying between 0.6 inches gravity driven, varying between 0.6 inches per day (in sandstones) to several inches per day (in sandstones) to several inches per year (in granitics)per year (in granitics)

The source of groundwater is rain and The source of groundwater is rain and melt water infiltrating and percolating melt water infiltrating and percolating through fractures/pores in soil and bedrockthrough fractures/pores in soil and bedrock

GROUNDWATER MOVEMENT GROUNDWATER MOVEMENT AND SOURCESAND SOURCES

How much groundwater is there?How much groundwater is there?

Estimates of up to 4 million kmEstimates of up to 4 million km33 for groundwater for groundwater Surface water – 160,000 kmSurface water – 160,000 km33

Extraction of groundwater measured in ‘acre-Extraction of groundwater measured in ‘acre-feet’ (the amount of water that covers one acre feet’ (the amount of water that covers one acre of land, one foot deep)of land, one foot deep)

California extracts 17-20 million acre-feet (maf) California extracts 17-20 million acre-feet (maf) per yearper year

The Ogallala Aquifer in central United States The Ogallala Aquifer in central United States produces 110 maf per year (317 billion gallons produces 110 maf per year (317 billion gallons of water per year)of water per year)

GROUNDWATER USAGEGROUNDWATER USAGE

WHO USES GROUNDWATER?WHO USES GROUNDWATER?

Almost all humans will use groundwater – Almost all humans will use groundwater – either directly pumping it into their own either directly pumping it into their own cistern or through major metropolitan cistern or through major metropolitan water transportation systems.water transportation systems.

Where is Groundwater Stored?Where is Groundwater Stored? Groundwater is stored in rock bodies called Groundwater is stored in rock bodies called aquifers.aquifers. A good aquifer provides both storage and transmittal A good aquifer provides both storage and transmittal

of groundwaterof groundwater Characteristics of aquifers:Characteristics of aquifers:

PorosityPorosity• The number and size of pore spaces, fractures, joints, in The number and size of pore spaces, fractures, joints, in

bedrockbedrock• Provides Storage for groundwaterProvides Storage for groundwater

PermeabilityPermeability• The connectedness of pore spaces, fractures, joints in The connectedness of pore spaces, fractures, joints in

bedrockbedrock• Provides Transmittal for groundwaterProvides Transmittal for groundwater

What Bedrock makes a Good What Bedrock makes a Good Aquifer?Aquifer?

Any bedrock with both good porosity and Any bedrock with both good porosity and good permeabilitygood permeability Unconsolidated sedimentary rockUnconsolidated sedimentary rock SandstonesSandstones Fractured igneous rocks (basalt) or jointed Fractured igneous rocks (basalt) or jointed

limestone limestone

POROSITY and PERMEABILITYPOROSITY and PERMEABILITY

POROSITY

PERMEABILITY

What if bedrock only has good What if bedrock only has good porosity or only permeability?porosity or only permeability?

Bedrock with good porosity but poor Bedrock with good porosity but poor permeability are call permeability are call aquicludesaquicludes or or aquitardsaquitards

These types of bedrock may store water, These types of bedrock may store water, but cannot transmit it.but cannot transmit it. Unfractured igneous rockUnfractured igneous rock Metamorphic rockMetamorphic rock Bedrock with high amounts of clayBedrock with high amounts of clay

• Shales, claystones, mudstones, siltstonesShales, claystones, mudstones, siltstones

What Is An Unconfined Aquifer?What Is An Unconfined Aquifer?

An unconfined aquifer has little to no overlying An unconfined aquifer has little to no overlying sedimentary layers.sedimentary layers. There is no confining layer of clay or other There is no confining layer of clay or other

impermeable sedimentary layersimpermeable sedimentary layers

The largest unconfined aquifer in the United The largest unconfined aquifer in the United States is the Ogallala Aquifer which extends States is the Ogallala Aquifer which extends from Texas through Oklahoma, Kansas, from Texas through Oklahoma, Kansas, Nebraska and North Dakota, plus parts of Nebraska and North Dakota, plus parts of Wyoming, Colorado and New Mexico.Wyoming, Colorado and New Mexico.

UNCONFINED AQUIFERUNCONFINED AQUIFER

OGALLALA AQUIFEROGALLALA AQUIFER

What is a Confined Aquifer?What is a Confined Aquifer?

Confined Aquifers are usually sandwiched Confined Aquifers are usually sandwiched between two non-permeable layers.between two non-permeable layers.

The confining layers provide pressure on The confining layers provide pressure on the aquifer, allowing the groundwater to the aquifer, allowing the groundwater to rise to the surface under its own energy – rise to the surface under its own energy – no pumping required: Artesian Wellsno pumping required: Artesian Wells

Largest Artesian well in United States is Largest Artesian well in United States is the Big Spring in Missouri the Big Spring in Missouri Produces 300-400 million gallons of water/dayProduces 300-400 million gallons of water/day

CONFINED AQUIFERCONFINED AQUIFER

ARTESIAN WELLSARTESIAN WELLS

Decorative Waterwheel placed over original Artesian Wells in SFV (Sportsman’s Lodge)

Historic springs exist many places along Ventura Boulevard.

This is why the Spaniards established California's first highway, El Camino Real, along this long used pathway.

Photo in Archives of The Museum of the San Fernando Valley -2008 - Photo by Gerald Fecht

Big Spring, MissouriBig Spring, Missouri

AQUIFER ZONESAQUIFER ZONES The Vadose Zone: Zone of AerationThe Vadose Zone: Zone of Aeration

This is the upper zone of an aquiferThis is the upper zone of an aquifer Between each pore space and within each joint or fracture, both Between each pore space and within each joint or fracture, both

air and water can be storedair and water can be stored The Phreatic Zone: Zone of SaturationThe Phreatic Zone: Zone of Saturation

This is the lower zone of an aquiferThis is the lower zone of an aquifer Between each pore space and within each joint or fracture, only Between each pore space and within each joint or fracture, only

water is stored.water is stored. Represents the zone within the aquifer designatedRepresents the zone within the aquifer designated as ‘true as ‘true

groundwater’groundwater’ Water TableWater Table

This is the upper limit of the Phreatic Zone within an aquiferThis is the upper limit of the Phreatic Zone within an aquifer This is the boundary between the Vadose and Phreatic ZoneThis is the boundary between the Vadose and Phreatic Zone Depth of water table determined by wells – they will fill to the Depth of water table determined by wells – they will fill to the

level of the water tablelevel of the water table Lakes, springs, streams are ‘surface expressions’ of the water Lakes, springs, streams are ‘surface expressions’ of the water

tabletable

VADOSE AND PHREATIC VADOSE AND PHREATIC ZONESZONES

Phreatic zone

DIAGRAM OF AN AQUIFERDIAGRAM OF AN AQUIFER

CaliforniaCalifornia

Statewide AquifersStatewide Aquifers

LOS ANGELES GROUNDWATER BASINSLOS ANGELES GROUNDWATER BASINS

San Fernando Valley/San San Fernando Valley/San Gabriel Valley GroundwaterGabriel Valley Groundwater

San Francisco Area San Francisco Area GroundwaterGroundwater

Ventura County GroundwaterVentura County Groundwater

GROUNDWATER MANAGEMENT GROUNDWATER MANAGEMENT CHALLENGESCHALLENGES

LawsLaws Water Table DepletionWater Table Depletion Ground SubsidenceGround Subsidence ContaminationContamination

Laws on Groundwater UsageLaws on Groundwater Usage

Only two states of USA have no laws regarding Only two states of USA have no laws regarding the use of groundwater: Texas and Californiathe use of groundwater: Texas and California

The only requirement for the water to be of The only requirement for the water to be of “beneficial use”“beneficial use”

Recent attempts in California’s Legislature to Recent attempts in California’s Legislature to regulate groundwater have been met with strong regulate groundwater have been met with strong resistance from many groups: farmers, resistance from many groups: farmers, municipalities includedmunicipalities included Most recent ‘water bill’ passed has some restrictions, Most recent ‘water bill’ passed has some restrictions,

but groundwater still not regulatedbut groundwater still not regulated

GROUNDWATER WITHDRAWALSGROUNDWATER WITHDRAWALS

WATER TABLE DEPLETIONWATER TABLE DEPLETION

Water table depletion can be the result of Water table depletion can be the result of natural droughts as well as human activitynatural droughts as well as human activity

Over-pumping wells can result in Over-pumping wells can result in temporary and permanent lowering of the temporary and permanent lowering of the water tablewater table

NORMAL CONDITIONS FOR NORMAL CONDITIONS FOR WATER TABLEWATER TABLE

CONDITIONS FOR WATER CONDITIONS FOR WATER TABLE DEPLETIONTABLE DEPLETION

DRAWDOWN EFFECT AND DRAWDOWN EFFECT AND CONE OF DEPRESSION WITH CONE OF DEPRESSION WITH

RECOVERYRECOVERY

DRAWDOWN – NO RECOVERYDRAWDOWN – NO RECOVERY

lowered

GROUND SUBSIDENCEGROUND SUBSIDENCE

Over pumping groundwater can result in Over pumping groundwater can result in the sinking of overlying layers.the sinking of overlying layers.

Groundwater acts to ‘buoy’ up overlying Groundwater acts to ‘buoy’ up overlying sedimentary layers – remove the water sedimentary layers – remove the water and all the pore spaces, fractures, and and all the pore spaces, fractures, and joints can collapsejoints can collapse

SUBSIDENCESUBSIDENCEPicture from the San Joaquin Valley showing the amount of land subsidence since 1925 due to aggressive groundwater pumping

SUBSIDENCE IN CALIFORNIASUBSIDENCE IN CALIFORNIA

SUBSIDENCE IN CALIFORNIASUBSIDENCE IN CALIFORNIA

SUBSIDENCE IN TEXASSUBSIDENCE IN TEXAS

CONTAMINATIONCONTAMINATION

Groundwater contamination comes in Groundwater contamination comes in several waysseveral ways Landfills and septic tanksLandfills and septic tanks AgricultureAgriculture IndustrialIndustrial UrbanUrban Toxic wastesToxic wastes Salt water intrusionSalt water intrusion

SOURCES OF CONTAMINATIONSOURCES OF CONTAMINATION

LANDFILL CONTAMINATIONLANDFILL CONTAMINATION

GAS TANK CONTAMINATIONGAS TANK CONTAMINATION

Septic Tank ContaminationSeptic Tank Contamination

AGRICULTURE CONTAMINATIONAGRICULTURE CONTAMINATION

PesticidesPesticides InsecticidesInsecticides HerbicidesHerbicides FertilizersFertilizers Animal WasteAnimal Waste

AGRICULTURAL AGRICULTURAL CONTAMINATIONCONTAMINATION

INDUSTRIAL CONTAMINATIONINDUSTRIAL CONTAMINATION

San Fernando Valley/San Gabriel San Fernando Valley/San Gabriel Valley Groundwater contaminationValley Groundwater contamination

San Francisco Area Groundwater San Francisco Area Groundwater Basin ContaminationBasin Contamination

SALT WATER INTRUSIONSALT WATER INTRUSION