Supply, Renewal and Use of Water Resources Water • 97% by volume is found in the ocean Hydrologic Cycle• 3% is fresh water with 2.997% locked up in ice caps and glaciers • 0.003% easily available as soil moisture, usable groundwater, water vapor, lakes and streams
Surface Runoff – water that flows into streams, lakes, wetlands and reservoirs Watershed (drainage basin) -a region from which water drains into a stream, lake, reservoir, or other body of water. Groundwater Zone of Saturation – below the surface where voids are filled with water Recharge areaWater Table – the surface of the zone of saturation Aquifer – porous sand, gravel or bedrock through which groundwater flows • an area of land through which water passes downward or laterally into an aquifer Water mining – removal of water from an aquifer that exceeds its replenishment• Natural recharge or lateral recharge How do we use the world's fresh water? • 65% – irrigate farm land (agriculture) Too Little Water• 25% – energy production • 10% – domestic and municipal use Causes of Freshwater Shortages *Dry climate *Drought *Desiccation *Water Stress How Can Water Supplies be Increased? • Build dams and reservoirs Dams• Bring in surface water from another area • Withdraw groundwater • Desalination • Improve the efficiency of water use • capture and store water from rain and melting snow; then released as desired to produce elec. power, irrigate land, control flooding below the reservoir and provide water to towns • can reduce downstream flow to a trickle (Colorado River) • reduce biodiversity o Danube's Iron Gate dam Transferring water from one place to anothero China's Three Gorges project (Yangtze River) o Malaysia's Bakun dam – would be the world's highest *James Bay Watershed *Aral Sea Watershed Salt Rain – salty dust picked up by rainHow they are dealing with this problem of the Aral Sea • charging farmers more for irrigation water Tapping groundwater and converting salt water to fresh water• decreasing irrigation water quotas • introducing water-saving technology • dev. a regional integrated water management plan • planting protective forest belts • using underground water • improving health services • slowing the area's rapid population growth Overuse of groundwater can cause: • aquifer depletion Ways to slow groundwater depletion include• aquifer subsidence • intrusion of salt water into aquifers • controlling population growth Desalination• not planting water-thirsty plants in dry areas • wasting less irrigation water 1. Distillation 2. Reverse Osmosis • Uses vast amount of electricity. Cloud Seeding• Distribution of desalinated water is also costly • Process produces large quantities of brine (contains high levels of salt and minerals) • Add chemicals to clouds to promote rain Using Water More Efficiently• Legal issues over the ownership of water in clouds • Tow massive icebergs to arid coastal areas. • 65-70% of water used throughout the world is wasted: evaporation, leaks, etc. How can we waste less water in irrigation?• In U.S., artificially low water prices – government subsidies • Multiple water resource management responsibility • Line irrigation ditches (50-60% efficiency) How can we waste less water in industry, homes and businesses?• Use high efficiency center-pivot sprinkler system (70-80% efficiency) • LEPA – low energy precision application sprinklers (75-85% efficiency) • High-efficiency trickle or drip irrigation systems (80-90% efficiency) • Computer-controlled systems to monitor soil moisture and irrigate as needed. • Organic Farming – requires ~1/4 water of conventional farming. • Recycle aluminum (97% less water) Salmon – anadromous (living in both fresh and salt water environments)• Xeriscaping (use of dry climate vegetation) and drip irrigation for gardens and other vegetation • Eliminate leaks • Eliminate single rate billing systems (apartments and 1/5 of US public water systems) • Rebates for installing water-saving devices (showerheads, toilets) • "Negaliters" or "Negagallons" are savings in water used. • salmon ranching • To build up the salmon runs' o build hatcheries upstream Too Much Watero transport young salmon around dams o makes streams off limits for hydropower o obliterate old logging roads to reduce runoff of silt • Natural flooding How can we reduce flooding risks?• Floodplain • Humans contribute to flood deaths and damage by removing vegetation, living in the floodplains, through urbanization (highways, parking lots, etc.). Channelization (straightening and deepening streams) • reduces upstream flooding, increases upstream bank erosion and downstream flooding and deposition of sediment Building levees and dams• increases water's capacity for doing damage downstream Restoring wetlands• destruction happens downstream from each levee • the levee race • Flood control dam – the reservoir gradually fills up with sediment • gives a false sense of security Instituting floodplain management • The best approach from an environment viewpoint A Sustainable Water Future• "Sooner or later the river (or ocean) always wins" • preserve the ecological integrity of water supply systems Three underlying forces that can lead humans to use water in an unsustainable way:• waste less water • allow fair access to water • give people a say in how water resources are developed and used. • depletion or degradation of a shared resource A key to reducing water waste is for governments to phase out subsidies• population growth • unequal distribution or access |
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