Grotzinger Jordan Understanding Earth Seventh Edition Chapter 17

Grotzinger • Jordan Understanding Earth Seventh Edition Chapter 17: THE HYDROLOGIC CYCLE AND GROUNDWATER © 2014 by W. H. Freeman and Company

Chapter 17 The Hydrologic Cycle and Groundwater

About the Hydrologic Cycle • Hydrology 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 Earth.

Lecture Outline 1. The geologic cycling of water 2. Hydrology and climate 3. The hydrology of groundwater 4. Erosion by groundwater 5. Water quality 6. Deep water in the crust

1. 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 Earth.

1. The Geologic Cycling of Water

1. The Geologic Cycling of Water ● The hydrologic cycle ● precipitation ● infiltration and runoff ● evaporation, transpiration, and sublimation ● groundwater flow

1. The Geologic Cycling of Water The hydrologic cycle

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

2. Hydrology and Climate ● Key climatic factors ● relative humidity ● rainfall ● landscape

2. Hydrology and Climate ● Key tectonic factors ● ocean-land relationships ● mountain rain shadows

2. Hydrology and Climate: The Rain Shadow Effect

2. Hydrology and Climate ● The runoff-precipitation relationship ● stronger in local areas ● less strong in regional areas

2. Hydrology and Climate Average Annual Precipitation

2. Hydrology and Climate Average Annual Runoff

2. Hydrology and Climate ● Surface storage of water runoff ● lakes and reservoirs ● wetlands and swamps

The Hydrology of Runoff: Similarity of a Dammed Lake and a Natural Lake

The Hydrology of Runoff: Similarity of a Dammed Lake and a Natural Lake

Thought questions for this chapter How 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?

3. The Hydrology of Groundwater ● Groundwater flow through soil and rock ● porosity and permeability ● groundwater table

Groundwater: Porosity and the Amount of Open Space in Various Materials

3. The Hydrology of Groundwater

3. The Hydrology of Groundwater ● Above and below the groundwater table ● unsaturated (vadose) zone ● saturated (phreatic) zone

3. The Hydrology of Groundwater ● Inflow and outflow of groundwater ● recharge (influent streams) ● discharge (effluent streams)

Groundwater: Effluent Water Headed for a Stream

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

3. The Hydrology of Groundwater

3. The Hydrology of Groundwater ● Types of aquifers ● unconfined – has an aquiclude below ● confined – has aquiclude above and below

3. 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 conditions

3. The Hydrology of Groundwater ● Balancing recharge and discharge ● balance = stable water table ● excess recharge = rising water table ● excess discharge = falling water table

Groundwater: Excess Discharge and the Cone of Depression

Groundwater: Excess Discharge and the Movement of Salt Water

Groundwater: Excess Discharge and the Movement of Salt Water

3. The Hydrology of Groundwater ● Speed of groundwater flows ● hydraulic gradient ● hydraulic conductivity ● Darcy’s law

Groundwater: Darcy’s Law Q = A [K ( ha – hb )] l

Water resources from major aquifers: ● Some major U. S. aquifers ● U. S. Great Plains and Midwestern states ● Ogallala aquifer

Water Resources: U. S. Withdrawal

Water Resources: The Great Ogallala Aquifer – only a few years left

Thought questions for this chapter If 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?

4. Erosion by Groundwater ● Features of groundwater erosion ● caves and caverns ● stalactites and stalagmites ● karst features (karst topography) ● sinkholes

4. Erosion by Groundwater ● Characteristics of areas with karst ● high rainfall and abundant vegetation ● limestone bedrock with joints ● significant hydraulic gradient

4. Erosion by Groundwater: Karst

Erosion by Groundwater: Carlsbad Caverns, New Mexico

Erosion by Groundwater: Sinkhole

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

5. Water Quality ● Contamination of the water supply ● lead pollution ● radioactive wastes ● microorganisms in water ● other chemical contaminants

5. Water Quality: Human Contamination

5. Water Quality ● 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 ppm

Thought questions for this chapter If it were 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?

6. Deep Water in the Crust ● Types of deep crustal groundwater ● meteoric water that seeps in ● magmatic water ● hydrothermal (hot spring) water

Water Deep in the Crust: The Origin of Hot Springs and Geysers

Mammoth Hot Springs, Yellowstone National Park

6. Deep Water in the Crust ● 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 minerals

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

Key terms and concepts Aquiclude Aquifer Artesian flow Darcy’s law Discharge Drought Groundwater table Hydraulic gradient Hydrologic cycle Hydrology Hydrothermal water Infiltration Karst topography Meteoric water

Key terms and concepts Permeability Potable Precipitation Rain shadow Recharge Relative humidity Runoff Saturated zone Sinkhole Unsaturated zone