Understanding Earth Fifth Edition

Transcription

1 Understanding Earth Fifth Edition Grotzinger Jordan Press Siever Chapter 17: THE HYDROLOGIC CYCLE AND GROUNDWATER Lecturer: H Mohammadzadeh Assistant professors, Department of Geology, FUM Copyright 2007 by W. H. Freeman and Company Chapter 17 The Hydrologic Cycle and Groundwater 1

2 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 the Earth. Lecture Outline 1. Flows and reservoirs 2. Hydrology and climate 3. The hydrology of runoff 4. Groundwater 5. Water resources from major aquifers 6. Erosion by groundwater 7. Water quality 8. Water deep in the crust 2

3 1. Flows and reservoirs 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. 1. Flows and reservoirs 3

4 1. Flows and reservoirs The hydrologic cycle precipitation infiltration and runoff evaporation, transpiration, and sublimation groundwater flow The hydrologic cycle 4

5 The hydrologic cycle 2. Hydrology and climate Key climatic factors relative humidity rainfall landscape Key tectonic factors ocean land relationships mountain rain shadows 5

6 2. Hydrology and climate: the rain shadow effect 6

7 3. The hydrology of runoff The runoff precipitation relationship stronger in local areas weaker in regional areas 7

8 3. The hydrology of runoff Surface storage of water runoff lakes and reservoirs wetlands and swamps The hydrology of runoff: Similarity of a dammed lake and a natural lake 8

9 4. Groundwater Groundwater flow through soil and rock porosity and permeability groundwater table Groundwater: porosity and the amount of open space in various materials 9

10 4. Groundwater Above and below the groundwater table unsaturated (vadose) zone saturated (phreatic) zone Inflow and outflow of groundwater recharge (influent streams) discharge (effluent streams) Groundwater: effluent water headed for a stream 10

11 Groundwater: the water table 4. Groundwater: dynamics of the groundwater table 11

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13 4. Groundwater Types of aquifers unconfined has an aquiclude below confined has an aquiclude above and below Characteristics of some confined aquifers artesian (flowing) wells artesian flow (under pressure) 4. Groundwater: artesian conditions 13

14 4. Groundwater Complex geological environments perched water tables unpredictable flow conditions 4. Groundwater Balancing recharge and discharge balance = stable water table excess recharge = rising water table excess discharge = falling water table 14

15 Groundwater: excess discharge and the cone of depression Groundwater: excess discharge and the intrusion of salt water 15

16 4. Groundwater Speed of groundwater flows hydraulic gradient Darcy s law Q = A (K h ) l h l 16

17 Groundwater: Darcy s law x 5. Water resources from major aquifers Some major U.S. aquifers U.S. Great Plains and midwestern states Ogallala aquifer Water resources: U.S. withdrawal 17

18 6. Erosion by groundwater Features of groundwater erosion caves and caverns stalactites and stalagmites karst features (karst topography) sinkholes Characteristics of areas with karst high rainfall and abundant vegetation limestone bedrock with joints significant hydraulic gradient 6. Erosion by groundwater: karst 18

19 Erosion by groundwater: Carlsbad Caverns, New Mexico Erosion by groundwater: sinkhole in Winter Park, Florida 19

20 Key terms and concepts Aquiclude Aquifer Artesian flow Darcy s law Discharge Groundwater Groundwater table Hydraulic gradient Hydrologic cycle Hydrology Hydrothermal water Infiltration Karst topography Meteoric water Permeability Potable water Precipitation Rain shadow Recharge Relative humidity Reservoir Runoff Saturated zone Sinkhole Unsaturated zone 20