Water Resources Q: What water can we use? A: 97.4% of Earth’s water is salt 2.5% of Earth’s water is frozen 0.014% is available for human use

Earth’s Water System Fresh water is found in 2 locations: 1) Surface Water - water that remains above ground & does not evaporate - examples- streams, lakes, wetlands - watershed/drainage basin - area that funnels water into surface locations

Groundwater Features

2) Groundwater - water that permeates downward below the soil’s surface Groundwater Terms zone of saturation- underground areas filled with water. water table- top of the zone of saturation zone of aeration- porous areas available for H2O aquifers- areas where groundwater flows

Groundwater Features

Saltwater Intrusion

Global Water Use - 70% is used for agriculture - 20% is used for industry - 10% is for residential use

Causes of Water Shortages Drying climates Increased droughts Desiccation - drying due to human activities Water stress - over-consumption due to population growth Unequal distribution

Solutions to water shortages Build dams & reservoirs Transport surface water to needy areas Withdraw more groundwater Desalination (converting salt to fresh) Increase water conservation Import food

Aspects of Dam & Reservoir Usage Pros 1) Controls floods 2) Produces cheap hydroelectric power 3) Supplies year round irrigation 4) Provides recreational areas 5) Increases runoff for human use

1) Increases water loss through evaporation Cons 1) Increases water loss through evaporation 2) Relocation of people & wildlife 3) Disrupts spawning of fish 4) Slows movement of nutrient-rich silt downstream 5) Decreases amount of water returning to oceans 6) Increase salinization downstream

The Aral Sea Disaster

- water supply year round - no evaporation loss - less expensive Tapping Groundwater Pros - water supply year round - no evaporation loss - less expensive - provides 1/3 of world’s water (51% in U.S.) Cons - decreases water table, depletion of aquifer - aquifer subsidence (sinking of land) - salt water intrusion (coastal areas) - chemical contamination of groundwater - reduces stream flow

Desalination - converting salt water into fresh water 2 Ways: 1) Distillation - heating to evaporation & collecting condensed water 2) Reverse Osmosis - passing salt water through membranes that catch salt molecules Problems - costly (2-3x more expensive) - creates large amounts of wastewater

Other Options for Water 1) Cloud Seeding - creating rain clouds by adding chemicals - difficult in dry regions (duh, no clouds) - increases pollutants in air & water 2) Towing Icebergs - mostly an idea - technology is unavailable

Water Conservation ? Why are we wasting water ? 1) Water subsidy policies - makes water cheap - creates false sense of water abundance 2) Current water laws - allows anyone along a river rights to it 3) Fragmented watershed management - too many groups overseeing same areas

Irrigation Conservation Problem Over 50% of irrigation water is wasted. Flood irrigation is primary method. Solution 1) Efficient sprinkler systems - modern sprinklers are 80-90% efficient 2) Use soil moisture detectors - allows for irrigation only when needed 3) Drip irrigation systems - use of pipes to deliver small amounts of water - 90-95% efficient - expensive 4) Use treated waste water for irrigation (gray water)

Commercial & Residential Conservation 1) Reuse water for irrigation 2) Raise water prices 3) Monitor water leaks 4) Use plants that require less water

Flooding Issues - Provides flood control - Creates fertile soil Natural Floodplain Benefits - Provides flood control - Creates fertile soil - Recharges groundwater Problems - Construction of dams & levees in floodplains - Removal of vegetation in floodplains for urban use - Diversion of streams in floodplains *Create dangerous situations during unusual rainfalls*