Chapter 11Water Resources and Water Pollution Avee Arvind, Kerry Norris, Elianna Cohen
Key Concepts • Will We Have Enough Usable Water? • How Can We Increase Water Supplies? • How Can We Use Water More Sustainably? • How Can We Reduce the Threat of Flooding? • How Can We Deal with Water Pollution?
Freshwater Is an Irreplaceable Resource That We Are Managing Poorly • Water is vital, yet we are poorly managing it • Water is a: • Global Health Issue • Economic Issue • Women’s and Children’s Issue • National and Global Security Issue • Environmental Issue
Most of the Earth’s Freshwater is Not Available to Us • Only about .024% of Earth’s Water is available to us as Liquid Freshwater • Freshwater supply is continuously collected, purified, recycled, and distributed in the earth’s hydrologic cycle
We Get Freshwater From: Ground Water Surface Water • Groundwater-Water in spaces between soil, gravel, holds very little • Zone of Saturation-Filled with water. Top of this zone is the water table • Aquifers- Water-tight Sponges made of Earth -Replenished through natural or lateral recharge • Surface Water- Freshwater that flows across land surface into larger water bodies • Surface Runoff-Precipitation that does infiltrate the ground or go into atmosphere • Watershed (drain-age basin)- Land from which water drains into a large body of water.
The Colorado River Story • Provides water/electricity for 30 million • Too much water drawn, very little reaches sea • Water shortage is arguably the most serious environmental problem the world faces during this century!!!!!
We Use a Large and Growing Portion of the World’s Reliable Runoff • Reliable Surface Runoff- 1/3 of annual surface that humans can actually use • Increasing Population Size = Increase in Withdrawal. • Now we use 34%, in 2025 we will use 70%
Freshwater in the U.S. • US freshwater is unevenly distributed • 79% is used for irrigation and heat removal • In East, most serious water problems: flooding, urban shortages and drought. • In arid/ semi-arid west, irrigation=95% of water • Projected that 36+ states = shortages by 2013 • Colorado River
Water Shortages Will Grow • Main Factors that Cause Water Scarcity:Drought, Dry Climate, Too Many People • Today, 30% of earth experience drought, 45% by 2059 • Conflicts among nations over water are going to grow • About 1 billion people don’t have access to clean water • By 2025, 3 billion won’t have access to clean water
Several Ways to Increase Freshwater Supplies • Reduce unnecessary waste of water • Increase water supplies in water-short areas by: • Withdrawing Groundwater • Building dams and reservoirs • Transporting surface water • Desalinization
Water Tables • When groundwater is withdrawn faster then replenished, water table fall • Aquifers supply water for half of the world. • In US, water pumped 4 times faster than replenished. • Most serious overdrafts is from our largest aquifer, Ogallala • Groundwater overdrafts near coastal area can contaminate groundwater.
Large Dams and Reservoirs Pros Cons • Capture/ Store runoff and release it as needed. • Control floods • Generate electricity • Supply water for irrigation and cities • Recreational activities • Displaced 40-80 million people from homes • Flooded area of productive land the size of CA • Impaired ecological services that rivers provide
CA Transfers Water from Water-rich Areas to Water-poor Areas • California Water Project uses giant dams, pumps, and aqueducts to transport • Climate change will sharply reduce water availability in CA • Best solution would be improving irrigation efficiency
Aral Sea Disaster: Unintended Consequences • Aral Sea shrinking from project to make largest irrigated areas • Since 1961, salinity rose seven fold, water level dropped 22km • 85% of wetlands have been eliminated • A huge area of lake now a human-made dessert • Wind distributes debris and kills organisms • Shrinkage has also changed climate • Since 1999, $600 million spent on trying to fix
Removing Salt from Seawater is Costly, Kills Organisms, and Produces Briny Wastewater • Desalinization-Removing dissolved salts from saltwater for domestic use. • Distillation-heating salt water until water evaporates from salt • Reverse Osmosis-High pressure to force saltwater through a membrane to remove salt • 13000 desalinization plant, meet less than .3% demand • Problems: High cost, Kills Marine organisms and needs lots of Energy, Produces high quantities of wastewater
Benefits of Reducing Water Waste • Quicker and Easier than providing new supplies • Two-thirds of world water is wasted • Half of Water in U.S. is wasted. • Feasible to reduce losses to 15% • Higher Prices = Less Wasted Water • Withdraw Subsidies that encourage waste = Less Wasted Water
We Can Cut Water Waste in Irrigation • 60% of water used in irrigation does not reach its targeted crops • More crop per drop strategy • Center-pivot, low pressure sprinkler. Gives 80% of water to crops • Gravity Flow: Low-energy , precision application sprinklers. Gives 90-95% of water to crops where it is needed. • Microirrigation (drip or trickle irrigation) Most effective (90-95%), Expensive 4% of fields uses drip irrigation in the US
Solutions: reducing irrigation water waste • Line canals bringing water to irrigations ditches • Irrigate at night to reduce evaporation • Monitor soil dampness and add water only when needed • Grow several crops on each plot of land • Polyculture
We Can Cut Water Waste in Industry and Homes • 90% of United States water is used by industries • Some industries recapture, purify and recycle their water to reduce their cost. • Solutions: Reducing water waste in Homes and Business • Recycle water in industry • Use drip irrigation • Redesign manufacturing processes to use less water • Purify and reuse water for houses, apartments and office buildings. • Collect and reuse household water to irrigate lawns and no edible plants • Use waterless composting toilets • Flushing toilets is the largest use of domestic water in the US and accounts for ¼ of home water use. • 40-60% of water supply in major developing cities are lost to leaks • 50-75% of slightly dirty water from bathtubs, showers, dishwashers, and washing machines can stored and used as gray water to irrigate lawns.
We Can Use Less Water to Remove Waste • Human use TOO much water • in 40 years we are going to need the world’s entire reliable flow of water just to dilute and get ride of our own waste. • Sewage treatment plants waste nutrients that could be used for soil and fertilizer
Some Areas Get too Much Water from Flooding • Floodplain: a flat valley floor next to a stream channel. • Floodplains have many assets • Fertile soil • Ample water for irrigation • Rivers for transportation and recreation • Flat land suitable for crops • Building highways, and railroads • Floodplains are narrowed and straightened so they have a less chance of flooding (channelized) • Protective levees and walls • Dams created for reservoirs
Floods Floods can be good Floods are bad • deposits nutrients rich silt on floodplains • Recharge ground water and help refill wetlands, which supports biodiversity and aquatic ecological services • Kill many people year • Tens of billions of dollars in property damage • Partly humans faults
Human Impact • Removal of water absorbing vegetation • Replace vegetation with farm fields, pastures, pavement and buildings that cannot absorb rainwater • Draining and building on wetlands • Hurricane Katrina (2005) • Rise in sea-level from projected climate change • Reports in 2007 by OECD and IPCC projected that in the 2070’s 150 million people living in costal cities will be a high risk for flooding
Case Study: Living Dangerously on Floodplains in Bangladesh • Depend on moderate flooding grow crops • Floods became more frequent • 1998 a flood covered Bangladesh for 9 months • Drowned 2,000 people and left 30 million homeless • Destroyed ¼ of the country’s crops=starvation • 2002 and 2004 • 5 million homeless and flooded large areas of rice fields • Living here means people have to deal with storm surges, cyclones, and tsunamis • 2003, killed more than a million people and left tens of thousands homeless
Water Pollution Water pollution: Harms humans or other organisms, makes it unsuitable Point sources: Specific locations, eg. factories, oil tankers -Laws limit them Nonpoint: Broad, diffused areas, eg. cropland, livestock feedlocks, parking lots, golf courses 3 biggest causes -Agricultural activities: eroded sediment, fertilizers, pesticides, bacteria from livestock, salts from irrigation -Industrial facilities -Mining
Streams can self-cleanse with moderate levels of pollution • Cleanses biodegradable material through dilution and bacteria • Requires dissolves oxygen, takes it away from the organisms who need it -Oxygen sag curve -heat also causes this • US has laws that require companies to eliminate point sources -Not the case for developing countries -Industry pollutes 2/3 of India's water
Too Little Mixing+Little water flow=bad for pollution -Lakes are stratified into layers, which prevents vertical mixture of pollutants -No flow: -1 to 100 years for lakes, several days-weeks for streams Eutrophication: (85%) nutrient enrichment of lakes caused by runoff of nitrate, phosphate terms: oligotrophic, eutrophic, cultural eutrophication -during hot seasons, cyanobacteria "blooms" occur -decreases lake productivity and fish growth by decreasing photosynthesis -more aerobic bacteria are needed to deal with the anaerobic bacteria -smelly, toxic hydrogen sulfide and methane results Prevent or reduce: banning phosphates in detergents, soil conservation Clean up excess weeds, pump oxygen, use herbicides to prevent plant growth
Non-degradeablewastes stay in water • Pollution seeps into groundwater • So flow (not diluted or dispersed) • Little dissolved oxygen • No decomposing bacteria
Groundwater pollution threatens certain areas • Groundwater supplies 70% of drinking water for China • hazardous wastes are interjected into the ground, which seeps into aquifers/ drinking water • when wells are drilled in soils that are rich in toxic arsenic (cancer-causing), it makes the aquifers toxic • preventing groundwater contamination
Purifying drinking water Developed countries -Water stored in reservoir -allows matter to settle, dissolved oxygen increases -Water sent to a purification plant, which must meat government standards -Protecting watersheds more effective though Developing countries -Contaminated water exposed in sunlight -kills microbes in 3 hrs -decreased childhood disease (diarrhea) 30-40%
Stats to understand the problem Coastal areas (wetlands, estuaries, coral reefs, swamps) more severely affected by pollution • 40% of worlds population live near the coast More statistics: • 80% of marine pollution caused by land (harmful algal booms, aka red, brown, green "toxic tides"), some caused by cruise ships • 25% of people swimming in public beaches develop ear infections, fore throats, respiratory disease • 400oxygen depleted zones form yearly
Case Study: Ocean pollution from oil -Crude petroleum (raw oil directly from ground) and refined petroleum (gas, fuel) leak into ocean -from tanks, eg. Exoon -oil leaks from tank accidents decreased 75% since 1980 -primarily industry runoff -Effects of leaked hydrocarbons in oil -kill acquatic organisms -coat birds feathers -affect the feathers ability to insulate -affects a birds buoyancy (causes drowning among birds) -specifically affects bottom dwelling organisms such as crabs, oysters, mussels, clams -prevention by using oil tankers with double hulls
Reducing surface water from non point sources • Farmers can cover cropland with vegetation • Reduce the amount of fertilizer that they use • Refrain from using fertilizer on steeply sloped land • Integrated pest management • planting buffers around animal feedlots
Laws to Reduce Water Pollution • Federal Water Pollution Control Act • Limits water pollution, requires polluters to get permits • percent of streams found safe for swimming increased from 36 to 64% • annual wetland loss decreased 80% • however, fish still unsafe • 45% of streams still too polluted for swimming • 1987 Water Quality Act • discharge trading policy (market) • cons: pollution build up in certain areas
Sewage Treatment reduces water pollution • developing countries - septic tank-waste pumped into settling tank (oil rises to top, solids fall to bottom.bacteriacomposition), go into large drainage field (used by 1/4 US residents) • developed countries-primary sewage treatment: first step: screens and girl treatment removes large floating objects, san floats to bottom. Next step: Secondary sewage treatment: Aerobic bacteria removes 90% of dissolved organic wastes. • bleaching(removes water coloration), disinfection (kills disease carrying bacteria), chlorination • disinfectants cause health risks: cancer, miscarriages, immune and endocrine systems • Environmental Scientist Peter Montague wants industries to remove their hazardous wastes sent to municipal sewage treatment plants • Encourage industries to reduce waste of toxic materials • Composting toilet systems -plant nutrients in human wastes returned to soil.