Water Chapters 13, 8, & 20

Water Covers 71% of Earth’s surface

Water’s Importance Regulates climate Dilutes waste Sculpts Earth’s surface Major habitat

Water Supply 97% salt 3% fresh 2.976% in ice caps 0.024% available Groundwater, lakes, & rivers

Access to Water Supply Women and children’s issue Global health issue Economic issue National security issue

Hydrologic Cycle Natural recycling and purification Driven by solar energy and gravity

Human Affects on Hydrological Cycle

Water Supply: Groundwater Zone of Saturation Space in soil filled with water Water Table Top of zone of saturation Aquifers Natural recharge Lateral recharge

Water Supply: Surface Water Water flows across the earth’s surface Sources: precipitation & snow melt Watershed (drainage basin) Land from where water drains into a particular waterway

Case Study: US Freshwater Resources More than enough freshwater but… Unevenly distributed Polluted Droughts

Case Study: US Freshwater Resources Water hotspots Identified areas where competition for water may cause conflicts

Case Study: US Freshwater Resources Storages will grow due to: Dry climate Droughts Population increases Wasteful use

Case Study: The Colorado River Basin Spans 7 states 14 dams & reservoirs Supplied from snow melt of Rockies

Case Study: The Colorado River Basin Many uses include: Drinking water Electricity Crop irrigation Recreation ~30 million people Las Vegas Los Angeles San Diego

Case Study: The Colorado River Basin Major Problems: Colorado basin has dry lands Modest flow for size Legal pacts allocate for more water for human use than it can supply Amount of water reaching the mouth (Gulf of California) has dropped since 1960

How can we increase our water supply? Groundwater

Groundwater Most are renewable Provides drinking water for half the world Most are renewable

US Groundwater Supplies: Withdrawn at 4 times the replacement level Almost all rural drinking water 1/5 of urban water 37% irrigation Withdrawn at 4 times the replacement level

High Moderate Minor or none Groundwater Overdrafts: High Moderate Fig. 13.16a, p. 308 Minor or none

Case Study: Ogallala Aquifer Largest known aquifer Spans 8 states Irrigates the Great Plains Slow recharge = dropping water table Supplies springs – vital habitats

Case Study: California Central Valley Serious aquifer depletion Supplies ½ the country’s fruits & veggies

How can we increase our water supply? Groundwater Dams & reservoirs

Main goal of Dams Capture & store runoff Release runoff: Control floods Generate electricity Supply irrigation Recreation

Three Gorges Dam Yangtze River, China World’s largest power station 1994-2012 Video in picture

How can we increase our water supply? Groundwater Dams & reserviors Desalination

Desalination Removal of salt from ocean water Processes: Distillation (evaporate & condensate) Reverse osmosis (microfilter) Middle east the most; US #4

Desalination Problems: Expensive Large amounts of energy Disrupts marine ecosystems Brine waste

Ways that Humans Use Water

Ways that Humans Use Water

Ways that Humans Use Water 70% is used for agriculture 1/3rd of US water – irrigation

Ways that Humans Use Water 70% is used for agriculture 20% industry Electricity generation Cooling machinery Refining metals/paper

Ways that Humans Use Water 70% is used for agriculture 20% industry 10% household uses

Water Conservation Estimated 2/3rds of water wasted Why? Low cost Lack of government incentives

Irrigation Conservation

Household Conservation Fix leaks Landscape smart Water efficient appliances Recycle greywater