Transcript Chapter 20
Chapter 21 Water Supply, Use and Management Recall the hydrologic cycle. Groundwater and Streams • Groundwater – Water found below the Earth’s surface, within the zone of saturation, below the water table – Water table, recharge zones, discharge zones, aquifer, cone of depression • Effluent Stream – A type of stream where the main water source is from the groundwater • Influent Stream – A type of stream that is everywhere above the groundwater table and flows in direct response to precipitation Groundwater and surface water flow diagram. Notice the difference between the effluent and influent stream in regards to ground water. Diagram that illustrates some of the interactions between surface water and groundwater for a city with some agricultural land nearby. Water Supply: A U.S. Example • Water budget – a model that balances the inputs, outputs and storage of water in a system – Defines the natural variability and availability of water • Over 99% of the Earth’s water is unavailable or unsuitable for beneficial human use! • It is expected that the total water withdrawn from streams and groundwater in the U.S will decrease but the consumptive use will increase…HUM… Water budget for the U.S. bgd = billions of gallons per day Groundwater level changes as a result of pumping in the TexasOklahoma-High Plains Region. Water from the aquifer is being used much faster than it is being replaced. Desalination as a Water Source • Desalination: a technology to remove salt from water – Uses reverse osmosis • It is very expensive and costs a lot to transport this potable water • Uses a lot of energy and therefore not all that efficient Water Use Some Terms… • Off-stream use: – water removed from it’s source for use • consumption • In-stream use: – the use of rivers for navigation, hydroelectric power generation, fish and wildlife habitats and recreation In-stream water uses and volume of water flowing per second for each. The Aral Sea is drying up as a result of water diversion for agriculture. Some trends in U.S. fresh groundwater and surface water withdrawals and human population (1950-1995). Any Questions? Chapter 21 Part #2 Water Conservation - What is it? - The careful use and protection of water resources. 1. Agricultural Use 2. Domestic Use 3. Industry and Manufacturing Use 4. Perception and Water Use Comparison of agricultural practices in 1990 versus what they may be in 2020. What are some of the changes & why do you suppose they would occur? Sustainable Water Use • Def: The use of water resources by people in a way that allows society to develop and flourish into an indefinite future without degrading the various components of the hydrologic cycle or the ecological systems that depend on it What is something like this going to take? Variable source model for water supply for the city of Santa Barbara, California. Wetlands • Areas that are inundated by water or where the land is saturated to a depth of a few centimeters for at least a few days per year. • Wetlands serve a variety of functions that benefit ecosystems and people. Loss of marshlands in the San Francisco Bay & estuary from about 1850 to the present. Channelization and the Environment • Channelization: – An engineering technique that consists of straightening, deepening, widening, clearing, or lining existing stream channels – Purpose: • Control floods, improve drainage, etc. Flooding The most universal natural hazard in the world. • The frequency and severity are increased by urbanization. • Avoid building on floodplains – But do we do this? Why is managing the Colorado River so difficult? Any Questions?