Transcript Slide 1
Water Use, Overuse, and Natural Contamination Water Mining China Over-exploitation of renewable and non-renewable aquifers India Withdrawals exceed recharge creating deficits in the aquifer Israel Iran Jordan Mexico Lack of contemporary recharge Morocco Pakistan Saudi Arabia South Korea Spain Syria Tunisia United States Yemen The Middle East GROUNDWATER . (Mm3/yr) COUNTRY Total use % Non-renewable Saudi Arabia 21,000 84% Bahrain 258 35% Egypt 4,850 18% Jordan 486 35% Libya 4,280 70% Yemen 2,200 32% Saudi Arabia and Libya, use 77% of the estimated total world extraction of non-renewable groundwater for urban supply and irrigated agriculture. Pakistan Falls in the water table between 1982 and 2000 range from 3 to 6 feet per year Within 15 years Quetta will run out of water if the current consumption rate continues Iran: Water Refugees Mashad Villages Abandoned over pumping by an average of 5 billion tons (3.7 Ma-f)of water per year Equivalent to 1/3 Iran’s annual grain harvest Water table falling by 8.5 feet per year Qa-Disi Aquifer Paleowater 35,000 years old Saudi farmers are now pumping water from wells that are 4,000 feet deep 71 percent drop in wheat harvest from a high of 4.1 million tons in 1992 to 1.2 million tons in 2005, Yemen water extraction exceeds the annual recharge by a factor of five, Water table dropping 6 meters (18 ft) per year pumped dry by 2010 Options: relocate the capital pipelines Other Large Deficits ½ the world’s India total use of China groundwater Pakistan Area = 1 acre for agriculture Pumping: 325 million acre feet Recharge: 205 million acre feet Deficit: 120 million acre feet 1 acre-foot = 325,851 gallons 1 foot Shallow , unconfined aquifer depleted Deficit feeds 100 million people Level of the deep aquifer is dropping nearly 3 meters (10 feet) per year Deep wells must reach more than half a mile to tap fresh water India Deficit of 80 million acre-feet Deficit feeds 200 million Failure of 246 surface irrigation projects 21 million wells $600 electric pumps (1% of GDP) 95 % water table falling by 20 feet per year 5 acres of land Pumps 3200 gallons/hr Irrigates alfalfa for 64 hours 24 times per year 4.9 million gallons water/yr Yield: 6.5 gallons milk/day 4.9 million gallons => 2400 gallons milk (2000 gallons water/ gallon milk) United States United States 1/3 of irrigation water comes from groundwater The 3 largest aquifers are in arid/semi-arid regions Ogallala Aquifer Midwest Central Valley Aquifer California Southwest Aquifer System Arizona, Utah, Nevada Deficit of 30 million acre-feet High Plains Aquifer (Ogallala) ¼ gone in areas of Texas, Oklahoma, Kansas Water table declines up to 100 feet in some areas Central Valley Aquifer (California) Pumping 15% more water than is replaced Water storage capacity has declined by 50% Southwest Aquifer (Utah, Nevada, Arizona) Pumping 50% more water than is replaced Phoenix Arizona Growing 2 acres/hr Among the highest water users Tucson tripled in population over the last 40 years Central Arizona Project Canal 335 miles long 44 billion gallons/yr 7% lost to evaporation Use, Overuse, Quality Contaminant Sources USTs Landfills Septic systems Urban Runoff Agriculture Industry Rainfall Natural Groundwater Contaminants India 21 million wells Tapping water as deep as 1,000 meters water table falling by 20 feet per year Deeper Wells and Fluoride Naturally occurring element in Granite which dissolves into the groundwater Water near the surface is generally unaffected Lowering water tables = deeper wells Deep groundwater contains high fluoride levels fluoride in water can be a cumulative poison Intentional Fluoridation of Water in the U.S. Fluoridation became an official policy of the U.S. Public Health Service in 1951. By 1960 water fluoridation had become widely used in the U.S. reaching about 50 million people. By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water. How does it work? Tooth enamel is made of a mineral called hydroxyapatite Ca5(PO4)3OH Bacteria in the mouth create acids (H+) Hydroxyapatite is subject to dissolution by acids (H+) Fluoridation changes the chemical composition of hydroxyapatite to a crystal less subject to acid dissolution Sodium fluorosilicate (Na2SiF6) Sodium fluoride (NaF) NaF Na+ + F- Ingestion of fluoridated water increases the F- concentration in saliva F- replaces OH in hydroxyapatite making fluoroapatite FCa5(PO4)3 OH Fluoroapatite is less soluble in acid than hydroxyapatite Fluoride concentrations In U.S. tap water 0.6 – 1.1 mg/L Lower values in warm climates Fluoride levels > 1.5 mg/L Dental Fluorosis Intake: 1.6 to 6.6 mg/day Colorado Brown Stain Permissible fluoride limit in India is 1.2 mg/L Fluoride levels between 5-25 mg/L have been found Fluoride levels > 10 mg/L Skeletal Fluorosis Intake 9 mg/day to 12 mg/day Fluorosis has risen from 1 million to 25 million and now to 60 million people in India. Groundwater and Arsenic Arsenic is Naturally Occurring occurs primarily in association with sulfur-containing minerals mean values of arsenic content in soils, the earth’s crust, and sediments are between 1.5, and 7.7 mg/kg Natural waters, in general, contain low levels of total arsenic Mobilization of arsenic in the environment arises from anthropogenic activities related to mining and ore processing, metallurgy, agriculture, wood preservation, and industry. Inorganic Forms of Arsenic AsO3-3 AsO4-3 Arsenite Arsenate Low Oxygen High Oxygen Arsenite is more toxic than arsenate, interfering with enzyme activities which catalyze metabolic reactions Arsenite compounds are also more mobile in the environment due to higher solubility compared to arsenate compounds Both arsenate and arsenite are chronic accumulative toxins “The World’s Largest Mass Poisoning” Bangladesh and W. India ranked among the world's 10 poorest countries Floodplain and Delta of the Ganges and Brahmaputra Rivers. Himalayas Floodplain: area paralleling a river that is periodically inundated Ganges-Brahmaputra Delta Deltas are formed from the deposition of sediment carried by the river as the flow leaves the mouth of the river Accumulation of thick muds in the floodplains and deltas Prior to 1970s One of the highest infant mortality rates in the world Principally due to waterborne disease. Ineffective water and sewage systems Periodic monsoons and floods water-borne pathogens cholera, dysentery Deaths Due to Surface water contamination: 250,000/yr Deaths Due to Surface water contamination: 250,000/yr The Solution: Tap groundwater resources • easy • inexpensive First 1 million were sunk with aid from World Governments UNICEF World Bank 12 million hand-operated tube wells deliver water to over 80% of the rural village population Infant mortality and diarrheal illness reduced by 50% Wells in Floodplain and Delta Sediments Natural erosion of arsenic to waterbearing units. Well depths between 20m and 100 m Water Bearing Muds WHO/U.S limit: 10 ppb Bangladesh limit: 50 ppb Majority of wells > 50 ppb arsenic Some wells contain 500 - 1000 ppb Exposure Estimates Above 50 ppb: 35 million Above 10 ppb: 57 million Early Symptoms: Skin lesions and thickening Strong skin pigmentation 2003 Studies 83 million people Bihar: 40% wells contaminated Red River Delta 11 million people First wells sunk 7 years ago End Lecture 17 Next: Florida’s Aquifers Sea Levels Temporary reestablishment of carbonate deposition Vulnerability One gallon of gasoline can contaminate 1 million gallons of drinking water 1 ppm Metals Nutrients Pesticides Petroleum Solvents