Understanding EarthSixth EditionChapter 17:THE HYDROLOGIC CYCLEAND GROUNDWATER 2011 by W. H. Freeman and Company

Grotzinger Jordan

Chapter 17The HydrologicCycle and Groundwater

About the Hydrologic CycleHydrology is the study of movements and characteristics of groundwater.The hydrologic cycle has a profound effect upon climate prediction. Water is vital so we must understand where to find water and how water supplies cycle through the Earth.

Lecture Outline

The geologic cycling of water2. Hydrology and climate3. The hydrology of groundwater4. Erosion by groundwater5. Water quality6. Water deep in the crust

The Geologic Cycling of Water Flows into a reservoir include inflows and outflows, and inflow equals outflow.

Reservoirs include all the places that water is stored in and on the Earth.

The Geologic Cycling of Water

The hydrologic cycle

precipitation

infiltration and runoff

evaporation, transpiration, and sublimation

groundwater flow The Geologic Cycling of Water

The hydrologic cycle The Geologic Cycling of Water

Thought questions for this chapterIf global warming caused evaporation from the oceans to increase greatly, how would the hydrologic cycle of today be altered?

Key climatic factors

relative humidity

rainfall

landscape2. Hydrology and Climate

Key tectonic factors

ocean-land relationships

mountain rain shadows2. Hydrology and Climate

2. Hydrology and Climate:The Rain Shadow Effect

The runoff-precipitation relationship

stronger in local areas

less strong in regional areas2. Hydrology and Climate

2. Hydrology and Climate

2. Hydrology and Climate

Surface storage of water runoff

lakes and reservoirs

wetlands and swamps2. Hydrology and Climate

The Hydrology of Runoff:Similarityof aDammedLake anda NaturalLake

The Hydrology of Runoff:Similarityof aDammedLake anda NaturalLake

Thought questions for this chapterHow might the hydrologic cycle have been different 18,000 years ago, at the Wisconsin glacial maximum, when much of North America, Europe, and Asia were covered with ice?

Groundwater flow through soil and rock

porosity and permeability

groundwater table3. The Hydrology of Groundwater

Groundwater:Porosity andthe Amountof Open Spacein VariousMaterials

3. The Hydrology of Groundwater

Above and below the groundwater table

unsaturated (vadose) zone

saturated (phreatic) zone3. The Hydrology of Groundwater

Inflow and outflow of groundwater

recharge (influent streams)

discharge (effluent streams)3. The Hydrology of Groundwater

Groundwater:Effluent WaterHeaded for aStream

3. The Hydrology of Groundwater:Dynamics of the Groundwater Table

3. The Hydrology of Groundwater

Types of aquifers

unconfined has an aquiclude below

confined has aquiclude above and below3. The Hydrology of Groundwater

Characteristics of some confined aquifers

artesian (flowing) wells

artesian flow (under pressure)3. The Hydrology of Groundwater

3. The Hydrology of Groundwater

Complex geological environments

perched water tables

unpredictable flow conditions3. The Hydrology of Groundwater

Balancing recharge and discharge

balance = stable water table

excess recharge = rising water table

excess discharge = falling water table3. The Hydrology of Groundwater

Groundwater:ExcessDischargeand the Cone of Depression

Groundwater:ExcessDischargeand theMovement of SaltWater

Groundwater:ExcessDischargeand theMovement of Salt Water

Speed of groundwater flows

hydraulic gradient

Darcys law

Q = A (K h / l)3. The Hydrology of Groundwater

Groundwater: Darcys Law

Some major U.S. aquifers

U.S. Great Plains and midwestern states

Ogallala aquiferWater resources from major aquifers:

Water Resources: U.S. Withdrawal

WaterResources:The GreatOgallalaAquifer only a fewyears left

Thought questions for this chapterIf you lived near the seashore and started to notice that your well water had a slightly salty taste, how would you explain the change in water quality?

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

Your new house is built on soil-covered granitic bedrock. Although you think that prospects for drilling a successful water well are poor, a well driller who is familiar with the area says he has drilled many good water wells in this granite. What arguments might each offer to convince the other?

Features of groundwater erosion

caves and caverns

stalactites and stalagmites

karst features (karst topography)

sinkholes4. Erosion by Groundwater

Characteristics of areas with karst

high rainfall and abundant vegetation

limestone bedrock with joints

significant hydraulic gradient4. Erosion by Groundwater

4. Erosion by Groundwater: Karst

Erosion by Groundwater: CarlsbadCaverns, New Mexico

Erosion by Groundwater: Sinkhole in Winter Park, Florida

Thought questions for this chapterYou are exploring a cave and notice a small stream flowing on the cave floor. Where could the water be coming from?

Contamination of the water supply

lead pollution

radioactive wastes

microorganisms in water

other chemical contaminants 5. Water Quality

5. Water Quality: Human Contamination

Reversing contamination

easier if recharge rate is fast

usually costly and very slow

decontamination after pumping

in-ground water treatments 5. Water Quality

Dissolved materials in drinking water

potable water has 150 ppm

distilled water has < 1 ppm

some elements have their limits

example: arsenic, 0.05 ppm5. Water Quality

Thought questions for this chapterIf you discovered that radioactive waste had seeped into groundwater from a nuclear processing plant, what kind of information would you need to predict how long it would take for the radioactivity to appear in well water 10 km from the plant?

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

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

Types of deep crustal groundwater

meteoric water that seeps in

magmatic water

hydrothermal (hot spring) water6. Deep Water in the Crust

Water Deepin the Crust:The Originof Hot Springsand Geysers

Mammoth Hot Springs,Yellowstone National Park

Ancient microorganisms in deep aquifers

active colonies of microbes that may have been there for millions of years are found in deep crustal groundwater

they live by dissolving minerals6. Deep Water in the Crust

Thought questions for this chapterWhat geologic processes would you infer are taking place below the surface at Yellowstone National Park, which has many hot springs and geysers?

AquicludeAquiferArtesian flowDarcys lawDischargeDroughtGroundwaterGroundwater tableHydraulic gradientHydrologic cycleHydrologyHydrothermal waterInfiltrationKarst topographyMeteoric waterKey terms and concepts

PermeabilityPotablePrecipitationRain shadowRechargeRelative humidityRunoffSaturated zoneSinkholeUnsaturated zoneKey terms and concepts