Chapter 17:Chapter 17:THE HYDROLOGIC CYCLE

AND GROUNDWATERAND GROUNDWATER

What Makes water so important?What Makes water so important?pp

About the Hydrologic CycleAbout the Hydrologic Cycle•• Hydrology is the study of movements Hydrology is the study of movements

and characteristics of (ground)water.and characteristics of (ground)water.

•• The hydrologic cycle has a profound The hydrologic cycle has a profound

effect upon climate prediction. effect upon climate prediction.

•• Water is vital so we must understand Water is vital so we must understand

where to find water and how water where to find water and how water

supplies cycle through the Earth.supplies cycle through the Earth.

Flows and reservoirsFlows and reservoirsFlows and reservoirsFlows and reservoirs

R i i l d ll th l● Reservoirs include all the places that water is stored in and on thethat water is stored in and on the Earth.

● Flows into a reservoir include● Flows into a reservoir include inflows and outflows

Flows and reservoirsFlows and reservoirs

• < 1% of world’s water is readily available for use. Globally, 70% of fresh water is used for agriculture, 20% for industry, 10% for residences.

• If all the polar ice caps melts, then sea-level will rise by 75 m.

Water: Residence timesWater: Residence times

Flows and reservoirsFlows and reservoirs

Th h d l i lTh h d l i l●● The hydrologic cycleThe hydrologic cycle

i it tii it ti●● precipitationprecipitation

i filt ti d ffi filt ti d ff●● infiltration and runoffinfiltration and runoff

ti t i titi t i ti●● evaporation, transpirationevaporation, transpiration

●● groundwater flowgroundwater flow

The hydrologic cycleThe hydrologic cycle--The hydrologic cycleThe hydrologic cyclepowered by solar energypowered by solar energy

Hydrology and climateHydrology and climate

● Key climatic factors

y gyy gy

● Key climatic factors● relative humidity● rainfall● landscape● landscape

● Key tectonic factorsl d l ti hi● ocean–land relationships

● mountain rain shadowsmountain rain shadows

Hydrology and climate:Hydrology and climate:the rain shadow effectthe rain shadow effect

Leeward slope

Windward slope

The hydrology of runoffThe hydrology of runoffThe hydrology of runoffThe hydrology of runoff

●● Surface storage of water runoffSurface storage of water runoff●● Surface storage of water runoffSurface storage of water runoff

●● lakes and reservoirslakes and reservoirs

●● wetlands and swampswetlands and swampswetlands and swampswetlands and swamps

GroundwaterGroundwater

●● Groundwater flow through soil Groundwater flow through soil and rockand rock

●● porosity and permeabilityporosity and permeabilityp y p yp y p y

d t t bld t t bl●● groundwater tablegroundwater table

GroundwaterGroundwater

• Porosity (φ): is the fraction of a porous material, which is void space

φ = Vvoid/Vtotal

Groundwater:Groundwater:

porosit andporosit andporosity andporosity andthe amountthe amountof open spaceof open spacein variousin variousin variousin variousmaterialsmaterials

GroundwaterGroundwater

●● Above and below the groundwater Above and below the groundwater tabletable

●● unsaturated (vadose) zoneunsaturated (vadose) zone( )( )

t t d ( h ti )t t d ( h ti )●● saturated (phreatic) zonesaturated (phreatic) zone

Groundwater:Groundwater:

thethethethewaterwatertabletable

GroundwaterGroundwaterTwo major zones of groundwater:

•Vadose Zone: zone above the water table (zone of aeration,(unsaturated).

•Zone of saturation: upper surface of saturation zone is [Groundwater] Water Table[Groundwater] Water Table.

Water Table mimics the ground topography, the height of which fluctuates with recharge/discharge.

GroundwaterGroundwaterGroundwaterGroundwater

●● Inflow and outflow of groundwaterInflow and outflow of groundwater

●● groundwater recharge (influentgroundwater recharge (influent●● groundwater recharge (influent groundwater recharge (influent streams or losing streams)streams or losing streams)g )g )

d t di h ( ffl td t di h ( ffl t●● groundwater discharge (effluent groundwater discharge (effluent streams)streams)streams)streams)

Groundwater:Groundwater:

effluent watereffluent watereffluent watereffluent waterheaded for aheaded for astreamstream

GroundwaterGroundwater• Aquifer: any lithologic formation that

stores groundwater (gravel, sand, sto es g ou d ate (g a e , sa d,limestone etc.). It not only stores but also transmits water at faster ratestransmits water at faster rates.

• Aquiclude: is a formation that may contain water but does not transmitsignificant quantities (clays and shales).

• Aquitard: is a formation with relatively low permeabilitypermeability.

GroundwaterGroundwater

●● Types of aquifersTypes of aquifers●● unconfined unconfined –– has an has an aquicludeaquiclude

belowbelowbelowbelow

●● confined confined –– has an has an aquicludeaquicludeabove and belowabove and below

●● PerchedPerched

Types of Aquifer:

UnconfinedUnconfined Aquiferqu e

Confined AquiferConfined AquiferConfined AquiferConfined Aquifer

●● Characteristics of some confined Characteristics of some confined aquifersaquifersaquifersaquifers

●● artesian (flowing) wells artesian (flowing) wells

●● artesian flow (under pressure)artesian flow (under pressure)●● artesian flow (under pressure)artesian flow (under pressure)

Groundwater: artesian conditionsGroundwater: artesian conditionsPotentiometric (peizometeric) surface: Imaginary level to which water rises due to hydrostatic pressure. y

GroundwaterGroundwater

●● Complex geological environmentsComplex geological environmentsp g gp g g

h d t t blh d t t bl●● perched water tablesperched water tables

●● unpredictable flow conditionsunpredictable flow conditions

Groundwater:Groundwater:perchedperched

ttwaterwatertabletabletabletable

Recharge of GroundwaterRecharge of Groundwater

●● Balancing recharge and dischargeBalancing recharge and discharge

Recharge of GroundwaterRecharge of Groundwater

●● Balancing recharge and dischargeBalancing recharge and discharge

●● balance = stable water tablebalance = stable water table

●● excess recharge = rising waterexcess recharge = rising watert blt bltabletable

●● excess discharge = falling excess discharge = falling water tablewater tablewater tablewater table

Groundwater:Groundwater:

e cesse cessexcessexcessdischargedischargeggand the and the cone ofcone ofcone of cone of depressiondepression

What is the consequence of over pumping (over draft)?over pumping (over draft)?

compaction and degradation of the aquifer

may trigger subsidence

When the well is dry, we learn the worth of water"When the well is dry, we learn the worth of water"B j i F kliB j i F kli-- Benjamin FranklinBenjamin Franklin

Groundwater:Groundwater:

Excess discharge andExcess discharge andExcess discharge andExcess discharge andThe intrusion of saltThe intrusion of saltwaterwater

Q. What is the consequenceQ. What is the consequencef lt t i t if lt t i t iof salt water intrusion of salt water intrusion

into aquifers? into aquifers?

Darcy’s LAW:yDarcy’s law provides an accurate description of the flow of ground water in almost all hydrogeologic environments.hydrogeologic environments.

Head loss h h determinesHead loss h1 - h2 determines flow rate

QQ KA(dh/KA(dh/dLdL))Q= Q= –– KA(dh/KA(dh/dLdL))

Q=Q= –– KA(dh/KA(dh/dLdL))Volumetric flow rate (Q)

Q Q KA(dh/KA(dh/dLdL))(m3/s or ft3/s)

hydraulic conductivity (K)Area of cross section perpendicular to flow (A)

(m/s or ft/s)

Area of cross section perpendicular to flow (A) Hydraulic gradient (dh/dL)dh h h (diff i h i ht f t l ldh =hin - hout (difference in height of water level in inlet and outlet peizometers)

The minus signs on the right hand reflects that the hydraulic head always decreases in the direction

f fof flow.

K represents the measure of the ability for flow (permeability) through porous media.

• Darcy Velocity or Flux ( or specific discharge) [q]: volumetric flow per unit area

q = Q /A = -K dh/dl Unit: L/TDarcy velocity is a fictitious velocity since it assumes that flow occurs across the entire cross-section of the soil sample. Flow actually takes place only through interconnected pore channels.

The average pore water velocity is termed the seepage velocity (v) and is given by:

where φ is the porosity of the porous media (varies v = q/φ = Q/(Aφ)

φ p y p (from 0 to 1).

Average rate of groundwater flow is ~ 15 m/day, may g g y, yreach up to 125 m/day.

Table. Typical Porosity and hydraulic conductivity of

Material Porosity (%) Hydraulic Conductivity

Table. Typical Porosity and hydraulic conductivity of selected Earth Materials.

y (%)(K) in m/day

UnconsolidatedClay 45 0.041

Sand 35 32.8Gravel 25 205

Gravel & Sand 20 82Rock

Sandstone 15 28.7Limestone/ Shale 5 0.041

Granite 1 0.0041

Numerical ProblemQ T ll l d 100 f i d if i hQ: Two wells are located 100 feet apart in a sand aquifer with a

hydraulic conductivity of 0.04 feet per day and 35% porosity. The head of well 1 is 96 ft and the head of well 2 is 99 ft.

Q What is the seepage velocity of water between the twoQ. What is the seepage velocity of water between the two wells?

Ans: v = q/φ = K/φ × dh/dlAns: v q/φ K/φ × dh/dl

= (0.04ft/day × 1/0.35) × (0.03) = 0.0034 ft/day.

Numerical Problem

Sedimentary rocksWell 1

Well 2Valley

1 km

4 km

Flo direction in alle

1 km

Sedimentary rocks

Flow direction in valley

The valley (blue) is 4 km wide, where 2 wells are drilled 1 km apart. The saturated zone below is 25 m thick, with K = 100 m/day. Porosity

Q What is the discharge Q (m3/day) of aquifer?

, y y(φ) of material is 30% (0.3). The elevation of water in wells 1 and 2 are 98 and 97 m respectively.

10,000 m3/dayQ. What is the discharge, Q (m /day) of aquifer?Q. What is the time travel (T) of groundwater between

wells 1 and 2? This helps in studying contaminant

10,000 m /day

wells 1 and 2? This helps in studying contaminant transport. 3000 days

Erosion by groundwaterErosion by groundwater

●● Features of groundwater erosionFeatures of groundwater erosion

y gy g

●● Features of groundwater erosionFeatures of groundwater erosion

●● caves and cavernscaves and caverns

●● stalactites and stalagmitesstalactites and stalagmites

●● karstkarst features (features (karstkarst topography)topography)

●● sinkholessinkholes●● sinkholessinkholes

Erosion by groundwater: Erosion by groundwater: karstkarsty gy g

Satellite View K t— Karst

Topography

What are the EnvironmentalWhat are the Environmental concerns in karst terranes?

sinkhole collapse

Winter Park, Florida 1981: 100 m depression, 13 m deep, $2 million in damage

Susceptible to pollution from above2+ 2+hard water problem: amount of Ca2+ and Mg2+ in

water; difficulties with plumbing

thin residual soils, terra rosas, which makes waste burial or disposal management considerably difficultdifficult.

Erosion byErosion byyygroundwater:groundwater:

CarlsbadCarlsbadCaverns,Caverns,NewNewNew New MexicoMexico

Erosion byErosion byyygroundwater:groundwater:

sinkholesinkholein in Winter ParkWinter ParkWinter Park,Winter Park,FloridaFlorida

100 m wide, 13 m deep, $2 million in damage

Groundwater Uses

Why should we be concerned about groundwater pollution?groundwater pollution?

Groundwater Pollution is difficult to detect.

Groundwater has long-term residency (1000 yr), which means if polluted then it stays there for a long time.y g

Difficult and expensive to clean aquifers.

What steps can be taken to characterize groundwater pollution?

• Geologic characterization(lithology structure)(lithology, structure)

• Hydrologic characterization: depthHydrologic characterization: depth of water table, thickness of aquifer, direction and rate flow etcdirection and rate flow etc.

• Contaminant (type & source)Contaminant (type & source) identification and understanding the transport mechanismstransport mechanisms.

Aquifer ContaminationAquifer Contamination

Although unconfined aquifers are used for water supply, they are often contaminated by wastes and chemicals at the surface.

Confined aquifers are less likely to be contaminatedConfined aquifers are less likely to be contaminated and thereby provide supplies of good quality.

Water QualityWater Quality●● Contamination Source of water Contamination Source of water

llsupplysupply• Oxygen-demanding waste• Pathogenic organisms• NutrientsNutrients• Oil & Petroleum Products

H d Ch i l• Hazardous Chemicals• Toxic Heavy Metals• Radioactive Materials (Ra 222)• Thermal PollutionThermal Pollution

A pollutant is any substance, excess exposure to which is known to be harmful to living organisms.

Water QualityWater Quality• Pathogenic organisms

C C-Common diseases are Cholera, typhoid, hepatitis, dysentery etc.-Cryptosporidiosis (caused by Cryptosporidium, aCryptosporidiosis (caused by Cryptosporidium, a protozoa infection in the gastrointestinal tract- standard measure of microbial pollution is to count f l lif b t i ( f b t i f d ifecal coliform bacteria (a group of bacteria found in human & animal intestine & wastes).

E. Coli (usually found in meat products), a type of ( y p ), ypcoliform bacteria causes illness and death.Acceptable limit for drinking water is 1 coliform per 100 mL of sample100 mL of sample.

Causes of Contamination: earthquakes, floods, storms etc., may damage sewer lines resulting in contamination of water supply.

EutrophicationEutrophication: Nutrients: NutrientsAcondition in aquatic ecosystem where high

pp

nutrient concentration stimulates growth of phytoplankton.

Higher amounts of nutrients in a water body help grow algae & aquatic plants, which cloud water & block sunlight. Underwater grasses, which serves as food for aquatic creatures dies. When algae die & decompose, O2 is used up, resulting in depletion of dissolved Oxygen.

• Hazardous Chemicals:• Hazardous Chemicals:– Toxic synthetic organic and inorganic compounds

dditi (M th l T b t l Eth MTBE) i– oxygen additives (Methyl Terbutyl Ether, MTBE) in gasoline in order to increase oxygen level of gasoline and decrease CO emissions MTBE isgasoline and decrease CO emissions. MTBE is water soluble and commonly detected as Volatile Organic Compound (VOC) in groundwater. Conc. g p ( ) gOf 20-40 μg/L (ppb) can cause difference in taste & odor.

– Common VOC are - gasoline, industrial chemicals such as benzene, toluene and xylene (a.k.a. BTX), formaldehyde (carcinogens) andformaldehyde (carcinogens), and tetrachloroethylene, perchloroethylene (principal dry cleaning solvent)dry cleaning solvent)

Oil & Petroleum ProductsOil & Petroleum Products• Oil discharge in to water involving oil-tanker accidents in

sea.

Case History: In 03/24/1989, the oil tanker, Exxon Valdez, spilled > 11 million gallons of crude oil in sea near Valdez, Al k ( ld’ t i ti & l i ll i h iAlaska (world’s most pristine & ecologically rich marine environment). Out of this 50 % deposited on the shoreline, 20% evaporated, and only 14% was collected by waste recovery

• In 1994 N Russia pipe line fracture resulted in about 4-80

recovery.

• In 1994, N. Russia, pipe line fracture resulted in about 4-80 million gallons of crude oil spill contaminating land & water.

• Sept 16, 2008. A crack in the diesel pipeline of the Indian Oil C ( OC) GCorporation (IOC) has led to oil spillage in Ganga

• Aug 22, 2009 - oil spill across a 100-km swath on the south Gujarat coast, threatens the marine bio-diversity in the National Guja at coast, t eate s t e a e b o d e s ty t e at o aMarine Park and Sanctuary. Two major oil refineries — Reliance and Essar.

Toxic SubstancesToxic Substances• Heavy Metals:Heavy Metals:

– Such as Pb, Hg, Zn, Cd, As are often deposited with natural sediments at the bottom of stream channels. Become incorporated into plants, crops, and thus animals and humans.

– Inorganic ions of such metals are toxic– Hg (from volcanic emissions, natural deposits) contamination of aquatic

systems.Methylation:- Change of inorganic Hg2+ to CH3Hg+ (methylmercury) due to

bacterial activity. CH3Hg+ is more toxic than Hg2+. The conc. of CH3Hg+

increases higher in the food chain.

Residence time of Hg in ocean = 80,000 yrs

Source of Water PollutionSource of Water Pollution

Surface water PollutionSurface water Pollution• Point source pollution:

– readily identifiable localized and/or confined sources such as industrial/municipal pipes, sewers that empty into streams or rivers.These pollutants controlled by on site treatment/– These pollutants controlled by on-site treatment/ disposal and are regulated by permit.

• Non-point source pollution:Non point source pollution:– Diffused and intermittent pollution– Influenced by factors such as climate, hydrology, y , y gy,

topography, vegetation, geology, urbanization etc. – Includes all sorts of pollutants entering the water

t f ( i ti id f l tsystem from any sources (e.g, insecticides from plant is washed away by rain and added to rivers)

Acid Mine Drainage Acid Mine Drainage –– nonnon--point source pollutionpoint source pollution

FeS + 3 75 O + 3 5 H O ⇔ Fe(OH) + 2 H SOOxidation of pyriteFeS2 + 3.75 O2 + 3.5 H2O ⇔ Fe(OH)3 + 2 H2SO4

RemediationRemediation

●● Reversing contaminationReversing contamination●● Reversing contaminationReversing contamination

●● easier if recharge rate is fasteasier if recharge rate is fast

●● usually costly and very slowusually costly and very slow

●● decontamination after pumpingdecontamination after pumping

●● inin--ground water treatmentsground water treatments●● inin ground water treatments ground water treatments

Groundwater TreatmentGroundwater Treatment• Treatment processes:

– Extraction Wells: Pump out contaminatedExtraction Wells: Pump out contaminated water and treat it by filtration, oxidation, reverse osmosis etc.

– Vapor Extraction: Using vapor extraction well and treatment.

– Bioremediation: using microorganisms to attenuate contamination.

– Permeable treatment bed: contact treatment as contaminated water plume moved through beds, which neutralizes contaminants by chemical, physical and/or bi l i lbiological processes.

Control System for C t i t d G dContaminated Ground Water

Extraction Wells

Water qualityWater qualityq yq y

Factors that determine the quality of drinking water:Factors that determine the quality of drinking water:• Acidity (pH) —should be around 7• Salinity (TDS) —should be <500mg/L

Di l d tit t• Dissolved constituentsOrganicInorganicg

• Pathogens

• Taste• Taste (bad taste due to too much of some dissolved constituents such as Fe, Cu, S, Cl))

•Toxic metal and organic contaminant levels

Quality Criteria of Indian Drinking WaterSet by Indian Standards Institution and Indian Council of Medical

Research (ICMR): ISI (IS:10500-1989)Research (ICMR): ISI (IS:10500-1989)Sl. No. Substance or Characteristic Prescribed by ISI

Requirement (DesirableLimit)Max. Permissible level

Prescribed by ICMRHighest Desirable Level

Maximum Permissible level

Max. Permissible level(1) (2) (3) (4) (5)1. Colour, Hazen Units 10 5 units 25 units2. Odour Unobjectionable Unobjectionable Unobjectionable3. Agreeable Unobjectionable Unobjectionable Unobjectionable4. Turbidity 10 NTU 5JTU 25 JTU5 Di l d lid /l 500 500 1500*5. Dissolved solids, mg/l 500 500 1500*6. pH value 6.5 to 8.5 7.0 to 8.5 6.5 to 9.27. Total hardness (as CaCO3), mg/l 300 300 6008. Calcium (as Ca), mg/l 75 75 2009. Magnesium (as Mg), mg/l 30 Not more than 50 mg/I

10 Copper (as Cu) mg/l 0 05 0 05 1 510. Copper (as Cu), mg/l 0.05 0.05 1.511. Iron (as Fe), mg/1 0.3 0.1 1.012. Manganese(as Mn),mg/1 0.1 0.1 0.513. Chlorides (as Cl), mg/l 250 200 100014. Sulfate (as SO4), mg/l 150 200 40015. Nitrate (as NO3), mg/l 45 20 **16. Fluride (as F), mg/I 0.6 to 1.2 1.0*** 1.517. Phenolic Compounds (as

C6H5OH),mg/I0.001 0.001 0.002

18. Mercury (as Hg),mg/l. 0.001 -- 0.00119. Cadmium(as Cd),mg/l 0.01 -- 0.0120. Selenium (as Se),mg/l 0.01 -- 0.0120. Selenium (as Se),mg/l 0.01 0.0121. Arsenic (as As),mg/l 0.05 -- 0.0522. Cyanide(as CN), mg/l. 0.05 -- 0.0523. Lead (as Pb),mg/1. 0.10 -- 0.1024. Zinc (as Zn), mg/l 5 -- --26. Chromium (as Cr6+), mg/1 0.05 -- --30 P ti id Ab t30. Pesticides Absent -- --31. Radio-active materials: --

a) Alpha emitters uc**** per ml,Max.

10-8 -- 3 pci/l*****

b) Beta emitters uc per ml, Max 10-7 -- 30 pci/1

Oct. 2008Oct. 2008

World-wide Hydrological Mapping and Assessment Programme (WHYMAP); United Nations Educational, Scientific and Cultural Organization (UNESCO) & German Federal Institute for Geosciences and Natural Resources (BGR)

A A mapmap of of aquiferaquifer zoneszones in India (1,2, 3: in India (1,2, 3: aquiferaquifer zoneszones))

1. Alluvial aquifers of Indo-Gangetic plains in the northern and eastern India. Also,Narmada and Tapi river alluvium, coastal alluvium, coastal sand dunes and coastal limestoneaquifers.

2. Aquifers in the alluvium, li t d t t i thlimestone, sandstone etc. in the inland sedimentary basins ofcentral and southern India.

3. Hard rock aquifers in the Basalt (Deccan Traps), Metamorphic rocks and Basement complexrocks and Basement complex(granite and gneiss).

Source: groundwater resources of the world and their use; United NationsEducational, Scientific and Cultural Organization (UNESCO) report 2004.

HydrologicalHydrological mapmap of India and of India and YieldYield PotentialPotentialYieldYield PotentialPotential

C t l G d W tCentral Ground Water Board (Ministry of Water ResourcesGovernment of India)Government of India)-http://cgwb.gov.in

Groundwater Resources of IndiaGroundwater Resources of India-- RechargeRecharge

The map shows groundwater changes in India during 2002-08, losses in red and gains in blue, based on GRACE satellite observations. Estimated rate of depletionEstimated rate of depletion of groundwater in northwestern India (Jaipurand New Delhi) is 33 cm (1 ft) of water per year over the past decade. Increases in groundwater in southern India are due to recentIndia are due to recent above-average rainfall, whereas rain in northwestern India was close to normal during the study period.

Loss is almost entirelyLoss is almost entirely due to human activity.

Credit: I Velicogna/UC IrvineCredit: I. Velicogna/UC Irvinepublished in the August 20 issue of Nature

Gravity Recovery and Climate Experiment (GRACE) satellite data

Watershed of IndiaCentral Ground Water Board(Ministry of Water ResourcesGovernment of India)-http://cgwb.gov.in

-Watershed atlas of India-Basin wise watershed maps availableavailable

Thought questions for this chapterThought questions for this chapterg q pg q p

11 If the Earth warmed causing evaporation from theIf the Earth warmed causing evaporation from the1.1. If the Earth warmed, causing evaporation from the If the Earth warmed, causing evaporation from the oceans to increase greatly, how would the hydrologic oceans to increase greatly, how would the hydrologic cycle of today be altered?cycle of today be altered?cycle of today be altered?cycle of today be altered?

2. If you lived near the seashore and started to notice that 2. If you lived near the seashore and started to notice that your well water had a slightly salty taste, how would your well water had a slightly salty taste, how would you explain the change in water quality?you explain the change in water quality?

3. Why would you recommend against extensive 3. Why would you recommend against extensive development and urbanization of the recharge area ofdevelopment and urbanization of the recharge area ofdevelopment and urbanization of the recharge area of development and urbanization of the recharge area of an aquifer that serves your community?an aquifer that serves your community?

4. Why should communities ensure that septic tanks are 4. Why should communities ensure that septic tanks are maintained in good condition?maintained in good condition?

Thought questions for this chapterThought questions for this chapterg q pg q p

5. Why are more and more communities in cold climates 5. Why are more and more communities in cold climates restricting the use of salt to melt snow and ice onrestricting the use of salt to melt snow and ice onrestricting the use of salt to melt snow and ice on restricting the use of salt to melt snow and ice on highways?highways?

6. You are exploring a cave and notice a small stream 6. You are exploring a cave and notice a small stream flowing on the cave floor. Where could the water be flowing on the cave floor. Where could the water be

i f ?i f ?coming from?coming from?

Key terms and conceptsKey terms and conceptsAquicludeAquicludeAquiferAquifer

y py p

AquiferAquiferArtesian flowArtesian flowDarcy’s lawDarcy’s lawDarcy s lawDarcy s lawDischargeDischargeGroundwaterGroundwaterGroundwater tableGroundwater tableHydraulic gradientHydraulic gradientHydrologic cycleHydrologic cycleHydrologic cycleHydrologic cycleHydrologyHydrologyHydrothermal waterHydrothermal wateryd ot e a ateyd ot e a ateInfiltrationInfiltrationKarst topographyKarst topographyMeteoric waterMeteoric waterPermeabilityPermeability

Key terms and conceptsKey terms and conceptsPotable waterPotable waterPrecipitationPrecipitation

y py p

PrecipitationPrecipitationRain shadowRain shadowRechargeRechargeRechargeRechargeRelative humidityRelative humidityReservoirReservoirRunoffRunoffSaturated zoneSaturated zoneSinkholeSinkholeSinkholeSinkholeUnsaturated zoneUnsaturated zone