Chapter 17: Water Use and Management Shutian Lu, Siri Nycklemoe, Jonathan Olsen, and Jeffrey Gruba Water Resources ● Water is a renewable resource; however, limitless exploitation of water resources will lead to disaster. ● 2 billion people now live in countries with insufficient fresh water. And the number could double in 25 years. ● War over water? ● Water resources are not unevenly distributed. Uneven Distribution ● Three factors control global water distribution: 1. Global atmospheric circulation → Hadley cell & Ferrell cell → high pressure, low precipitation → major desserts are on 30° belt 1. Proximity to water resources; 1. Topography; mountains & rain Major Water Compartments ● Redistribution of water often is described in terms of interaction between different water compartments. Compartment Proportion to The Total Average Residence Time Ocean 96.5% 3,000 to 30,000 years Ice and snow 1.76% 1 to 100,000 years Groundwater(saline and fresh) 1.69% Days to thousands of years Lakes (saline and fresh) 0.013% One to hundreds of years Soil moisture 0.001% 2 weeks to 1 year Atmosphere 0.001% 1 week Marshes, wetlands, rivers 0.0012% 1 week to years Global Ocean Currents “Global warming” does not mean “warmer”! Ocean currents act as a global conveyor system, redistributing warm and cold currents around the globe. Easily Available Freshwater is Scarce Frozen Water ● 87.2% of total freshwater is tied up in glaciers, ice caps and snow fields; ● Meltwater replenishes rivers; ● Colorado river gets water from snowpeck on Rocky mountain, and decreasing snowfall has caused drought in the western United States; ● Climate change further disrupts the pattern. Groundwater System ● 12% of total freshwater is groundwater ● Infiltration → the process that precipitation percolates through permeable rocks ● zone of aeration → upper soil that holds water and air ● zone of saturation → filled with water ● water table → the top of the zone of saturation ● aquifer → porous layers of sand, gravel or rock lying below the water table Groundwater System ● ● artesian well/spring recharge zones → where water infiltrates into an aquifer Northfield Water Supply “Water within the Northfield city limits is supplied from a groundwater source via four wells that range in depth from 365 to 410 feet. Water is drawn from the Jordan aquifer.” Surface Water ● 0.8% of total freshwater ● Rivers o precipitation, meltwater replenish streams; o discharge rate is used to measure the size of river ● Lakes o contain nearly 100 times as rivers and streams ● Wetlands o stabilize soil o hold runoff o allow time for infiltration Water Availability ● Freshwater: essential for life ○ settlement ● Renewable Water Supply: ○ from surface runoff & aquifers ■ ⅔ of water transported in rivers = flood water ■ dependable source = stable runoff ● provides 400,000 gallons per person per year Water Scarcity and Stress ● Water Scarcity: demand exceeds supply or restricted use ● Water stress: renewable water supply cannot meet fundamental ecosystem/human needs ○ competition ● Per capita Supply: ○ highest: wet, low population density ■ Iceland ○ lowest: dry, high pop. density ■ Bahrain, Egypt Water Scarcity and Stress ● Drought: frequent in semi-arid climate ○ water shortage ■ Dust Bowl ● 1931-39 ● lack of soil conservation practice ● plowing & wheat planting, no growth ● dried soil carried by wind ○ dust filled farms & homes ● throughout plains Drought in the US Dust Bowl John Wesley Powell ● First expedition on Colorado River ● US Geological Survey ○ Concluded: not enough water to support large, concentrated populations ■ Oasis settlements ■ Pop. in each jurisdiction → area water source ○ Denver, Los Angeles, Las Vegas, Phoenix John Wesley Powell Water Use ● Use is increasing 2x as fast as population growth ○ Industrialized vs. Developing Countries ● Withdrawal: total amount taken from body of water ○ most can be returned to circulation or reused ■ 170,544 gallons ● US vs Haiti ● Consumption: loss of water due to evaporation, absorption, and contamination ○ Libya, Yemen, Israel Water Use By Sector ● Agriculture: ⅔ worldwide withdrawal ○ 85% of consumption ■ India, Kuwait, US ● Aral Sea: Kazakhstan & Uzbekistan ○ 1975 to 2000, 75% surface area loss, 90% decrease in volume ■ Soviet Union: tributaries diverted ● Salt concentration doubled ○ Small Aral reclamation Aral Sea Reduction over Time Water Use By Sector ● Lake Chad: 60,000 years ago → Caspian Sea ○ 1960s → Lake Erie ○ Irrigation, drought ○ former lake bed = Bodele Depression ● Irrigation: inefficient practices ○ 1% of world cropland is watered by drip irrigation ● Domestic: only 1% worldwide withdrawal ○ domestic consumption = 10% on avg. ● Industry: 20% global withdrawal Typical Household Water Use in the US Lake Chad Freshwater Shortages Causes of Water Shortages ● Natural defects ● Over consumption by agriculture or industry ● Inadequate funds for purifying and delivering good water Many People Lack Access to Clean Water ● One billion people lack access to clean water and 2.5 billion people don’t have adequate sanitation ● Every year there are hundreds of millions of water related illnesses and five million deaths caused by lack of clean water ● However in recent years there has been improvements: o In 1990, 800 million people gained access to clean water o The percentage of rural families with safe drinking water has risen from 10% to 75% Groundwater ● Groundwater is the source of about 40% of the fresh water for domestic and agricultural uses in the US ● Half of Americans rely on groundwater for drinking ● Overuse problems o Drying of well and natural springs o Disappearance of surface waters (wetlands, rivers and lakes) The Ogallala Aquifer ● Ogallala Aquifer underlies 8 states between Texas and North Dakota ● Once held more water than all the freshwater rivers and streams on earth ● Heavy pumping has dried up wells and whole towns are being abandoned ● It will take thousands of years to refill Consequences of Aquifer Depletion ● Subsidence: settling of the porous formations causing them to collapse o San Joaquin Valley (CA) has sunk about 33 feet (10 m) in the last 50 years because of excess groundwater pumping o Mexico City has sunk about 26 feet which has caused ancient Aztec temples o Also leads to flooding in coastal cities ● Saltwater Intrusion: when saltwater from ancient oceans along coastlines intrude into aquifers because of excess use of freshwater reserves Saltwater Intrusion Case Study: Lake Mead ● Because of drought, climate change, and urban development Lake mead is estimated to possibly reach levels where they will not be able to produce power or provide water for agriculture o Lake levels have been dropping about 12 feet per year Lake Mead China’s South-Water-North Project ● Because of similar water loss, Northern China is getting drier, so much so that the Gobi Desert is moving Eastward towards Beijing, so China embarked on a water distribution project called South-Water-North o This proposed to build a canal to bring the water from the Yangtze River to northern China o However this may worsen pollution problems Dry up wetlands, possibly alter ocean circulation and climate along China’s eastern coast ● Some people believe it may be beneficial to do something like this from the Great Lakes to the South Western states, others disagree Dams Often Have Severe Impacts ● Pros: o Provide hydraulic power and water to distant cities ● Cons: o Evaporation o Force people from their homes and land o Can trigger earthquakes if in seismically active locations o Lethal to migratory fish o Sediment can block dams which decreases the life of the dam and have many environmental impacts China’s Sanmenxia Dam on the Yellow River Clean Canyon and Boulder Dams on the Colorado River Major Transboundary River Basins ● Water around the world is unevenly distributed Average Annual Precipitation Water and Climate Change ● May exacerbate water shortages caused by population growth, urban sprawl, wasteful practices, and pollution ● Drought is the most likely result of climate change o People will have to leave their towns because of too little drinking water or will become undernourished because lack of water and food o Could also lead to war and conflict to nations Examples: ● Israel and its neighbors because of the Jordan River ● Nomadic tribes in Kenya fought over water resources ● Caused genocide in Darfur ● Sadam Hussein cut off water flow to his enemies Getting By with Less Water ● In 2010, an agreement was made for the Klamath River in California to keep fish populations stable. ● The agreement asked farmers to conserve 10 to 25% of the water they have used for irrigation in the past and in return would receive a one-time payment to finance conservation measures. ● This way, farmers can save more water over time so that the water doesn’t have to be shut off when fish are endangered. ● With clearer guidelines, farmers can grow low-value crops (like alfalfa) and use a little land for high-value crops during dry years. Increasing Water Supplies ● Researchers have been trying to make it rain with a variety of techniques ● For example, seeding clouds with dry ice or potassium iodide particles has been tested with mixed results ● More recently, researchers have been having more success using hygroscopic salts which is being tested all over the world ● One kind of technology that shows potential is desalination of ocean water or brackish saline lakes and lagoons. Desalination Statistics ● Worldwide, there are 13,080 desalination plants that produce more than 12 billion gallons of water a day. This is expected to grow to about 26 billion gallons per day by 2015. ● The largest producer is Saudi Arabia at one-third of the world total. The U.S. is second, at one-fifth. ● Middle Eastern oil-rich states produce about 60 percent of desalinated water. ● Desalination is 3 to 4 times more expensive than other ways to get freshwater but totally worth it for countries with very little fresh water. How We Can Conserve ● ● ● ● Take a shorter shower Stopping leaks Washing cars, dishes, and clothes as efficiently as possible Invest in low-volume showerheads and efficient dishwashers and washing machines ● Buy a waterless or low volume toilet (the largest U.S. domestic water use is toilet flushing). https://www.youtube.com/watch?v=4LrUc0C7vW0 Water Recycling In California, water recovered from treated sewage constitutes the fastest-growing water supply, growing 30 percent per year. Purified sewage effluent is being used for everything from agricultural irrigation to flushing toilets. Prices and Policies ● Throughout U.S. history most policies in U.S. have generally worked against conservation ● In the eastern United States where water is common, those who lived along a river bank had the right to use as much water as they wanted as long as it didn’t interfere with quality or availability for those downstream ● In the drier western regions policy those who owned the water first can block the water from anybody else on the stream so long as the water is used for economic use. Under this system, water rights can be bought and sold. ● Now, with growing recognition that water is a finite resource, the United States and other countries are encouraging the most beneficial uses and discourage wasteful water uses by water pricing and allocation policies. Water Conservation at Olaf ● Buildings like Regents have water saving toilets ● Also have motion-activated sinks in many buildings to make sure no water is not turned off ● The dishwashers at the cafeteria use circulated water so they don’t use as much water