Water Resources Chapter 9

Water, water, everywhere… Most (97%) of Earth’s water is saltwater Of the 3% that is freshwater, <1% is available for us The rest is frozen or deep underground

Groundwater Aquifer – groundwater is located in small spaces within permeable layers of rock and sediment Unconfined aquifer – porous rock + soil; water can move in and out freely Confined aquifer – surrounded by impermeable layers Springs or artesian wells

Groundwater… Water table – the uppermost level of water saturation in the soil Groundwater recharge – water from precipitation that percolates back into the soil

Groundwater… Pumping water out of the ground faster than it can be recharged will cause a drop in the water table Wells near the coastline can suffer from saltwater intrusion as the freshwater is infiltrated with ocean water

Surface Water Streams, rivers, ponds, lakes, wetlands 3 largest rivers based on volume: Amazon in South America Congo in Africa Yangtze in China Human settlement and impacts Transportation Irrigation Agriculture

Surface water… Lakes – surface area versus depth and volume determine size Classification of lakes: Oligotrophic Low nutrient levels = low productivity Mesotrophic Moderate productivity Eutrophic Highly productive

Surface water… Wetlands – help to offset flooding during periods of heavy rainfall Also are very useful at absorbing pollutants

Atmospheric water Drought – lack of rainfall Harm ecosystems and humans Also impact soil: Harder for nutrients to cycle Dried soil more vulnerable to wind erosion Flooding – too much rainfall Also cause crop and property damage Ground has been paved Excess water can’t soak in

Humans alter water availability Flood control/prevention: Levees Mississippi River (New Orleans) Black Warrior River (Northport) Floodwaters move downstream Encourages development of floodplain Risk of collapse or breach Dikes Levees for ocean waters The Netherlands

Humans alter water availability… Dams – cross rivers to produce a reservoir Water used for consumption, generation of electricity, flood control, recreation Environmental issues: Disrupt ecosystems during construction Interfere with natural flow of water Silt behind the dam

Humans alter water availability… Aqueducts – carry water to another place New York City & Los Angeles Environmental issues Disruption of ecosystem during construction Less water available in ecosystem feeding the aqueduct Can cause international disputes

Humans alter water availability… Desalination – making saltwater fresh Distillation: boiled water leaves salt behind, steam is captured and cooled to condense Requires a lot of energy Reverse osmosis: water is forced through a membrane which blocks the salt More efficient and less costly Brine – super salty water waste

Water use Agriculture Irrigation: considerations – cost, amount of evaporation Furrow ~ 65% efficient Flood ~ 70-80% efficient Spray ~ 75-95% efficient Drip > 95% Hydroponic agriculture

Water Use… Industry Electrical generation: In the U.S. ~ ½ of all water used goes toward generating electricity Hydroelectric generation returns water to source Thermoelectric power plants use water to cool the system and it leaves as water vapor Refining metals and making paper Gallons used per kg made: Copper 116, Aluminum 108, Steel 68, paper 33

Water Use… Households ~ 10% of all water used in U.S.