06 Natural Resurces- Water Resources

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1 NATURAL RESOURCES -- WATER RESOURCES Water is the lifeline of environment. It is one of the three vital resources of the mankind. Set the stage for the evolution of life. All living things require water for survival. Water possesses unique physical and chemical properties. It can be frozen, melted, evaporated, heated and combined. It turns into a solid form at 0oC and to a vapour form at 100oC. Habitat for aquatic ecosystems and aquaculture systems and reserve for biodiversity. Most precious resource of mankind – has many in-stream and off-stream uses Water keeps on cycling endlessly in the environment through hydrological cycle. Enormous resources of water are available on the earth amounting to about 1404 million km3. Solar energy drives the water cycle through transpiration from the plants and evaporation from the water bodies which return back through rainfall and snow.

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2 Water distribution pattern on land · At global scale about 71% of earth’s surface is covered with water. · Total volume of water in hydrosphere is estimated to be 1.4 billion Km3 of which 97% is ocean water (unfit for human consumption) and rest 3% is available as fresh water. · 77.2% of fresh water is stored in glaciers and ice caps, 22.4% is ground water and just 0.4% is distributed in lakes, swamps, rivers and streams Oceans 1.32 x 109 Km 3 97.3% Polar ice caps glaciers 2.92 x 107 Km 3 2.14% Ground water 8.35 x 106 Km 3 0.61% Saline lakes & inland seas 1.04 x 105 Km 3 0.008% Fresh water lakes 1.25 x 105 Km 3 0.005% Atmosphere 1.30 x 104 Km 3 0.001% Rivers & Streams 1.25 x 10 3 Km 3 0.0001%

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3 Water available for human exploitation = 9000 Km3/year World population and water are unevenly distributed. Iceland has 68,500 M3 per capita/year of water while Bahrain virtually has no access to fresh water. Water withdrawal rates vary widely (US citizen consumes 70 times more water than Ghana citizen). Seasonal availability of water also varies widely. Water bodies -- Water bodies include ¨ River, Streams, lakes ¨ Wetlands & marshes, estuaries, mangrove forests, salt marshes & coastal wetlands. ¨ Shorelines & shallow ocean water systems ¨ Open Oceans

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4 Water bodies are ¨ Habitats for life-fish & wildlife-aquatic ecosystems ¨ Productive systems (Commercial fisheries) ¨ Water sources for municipal, industrial & agriculture activities ¨ Used as a medium for transportation ¨ Sinks for the wastes discharged ¨ Have aesthetic recreational & religious value ¨ Water bodies have waste assimilative & self cleaning capacities

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5 Water bodies are dynamic ¨ Rivers & streams can change their path, width & depth & even the flow velocities ¨ Can show seasonal fluctuations in flow rates, volume and depth ¨ The space occupied by them can change (Can shrink or can engulf additional land areas) Water use ¨ Water use by humans is of 2 types water withdrawl & water consumption - Water withdrawal : Some of the water withdrawn from a source may be returned to that source for reuse. - Water consumption: water which is taken up but not returned for reuse-mostly because of losses like evaporation or contamination.

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6 Fresh Water Availability ¨ Depending upon water availability, world nations are divisible into water rich, water stressed & water scarce nation (>2000, 1000-2000 & < 1000 m per year) ¨ According to 2002 report by United Nations about 500 million people live in water stressed or water scarce countries. ¨ Canada with only 0.5 % of the world population has 20% of the world’s usable fresh water. ¨ China with 21% of the world’s people has only 7% of the supply ¨ As per the United Nations estimates (2002) at least 101 billion people don’t have access to safe drinking water & 2-4 billion do not have adequate sanitation facilities. ¨ By 2004, two- third of the world population would be suffering from acute water shortage.

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7 - Water scarcity will cause annual global losses of 385 million tons of food production. - Since 1970’s water stress of scarcity has killed more than 24,000 people per year & created millions of environmental refugees. ¨ Dwindling water supplies the various part of the world would be a major factor inhibiting economic growth & development.

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8 Water allocation Patterns ¨ On a global average 70% of the water withdrawn each year is used for agriculture - In India 93% of water is used in agriculture sector. - Kuwait which is water poor nation, uses only 4% of water for watering the crops ¨ Industry uses about 25% global water - It varies from a high of 70% in European countries to as low as 5% in less developed countries. ¨ Municipal uses 10% of total water withdrawn.

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9 Causes of freshwater scarcity Dry Climate Drought- a period of 21 days or longer in which precipitation is at least 70% lower & evaporation is higher than normal Desiccation – drying of exposed soil due to deforestation & overgrazing by live- stocks Water Stress- low per capita availability of water caused by increasing numbers of people relying on limited runoff levels

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10 Ground Water ¨ Infiltering & percolation of some precipitation downwards through pores, fractures, crevices & other spaces in soil & rock forms ground water. - Pores, water saturated layers of sand, gravel or bedrock through which ground water flows are called aquifers. - Ground water normally moves from point of high elevation & pressure to points of lower elevation & pressure. Ground water moves very slowly about a meter in a year. - Eventually most ground water flows into rivers, lakes, estuaries & wetlands. - About 9.86 % of the total fresh water resources is in the form of groundwater. It is 35-50 times that of surface water supplies. - Till some time back groundwater was considered to be very pure but of late even groundwater aquifers have been found to be contaminated by leachates from sanitary landfills.

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11 ADVANTAGES & DISADVANTAGES OF WITHDRAWING GROUND WATER: Advantages Disadvantages 1. Good source of water for drinking and irrigation 1. Lowering of water tables by over-pumping 2. Available year round 2. Sinking of land (Subsidence) When water removed. 3. Exists almost everywhere 3. Polluted aquifers unusable for decades or centuries. 4. Renewable if not over pumped or contaminated. 4. Saltwater intrusion into drinking water supplies near coastal areas. 5. No evaporation losses 5. Reduced water flows into streams, lakes, estuaries & wetlands. 6. Cheaper to extract than most surface waters. 6 Increased cost, energy use & contamination from deeper wells.

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12 Surface Water : - Surface runoff is precipitation that does not infiltrate the ground or return to the atmosphere by evaporation.This run-off flows in the form of streams, lakes, ponds, and wetlands. - Largely used for irrigation, industrial use, public water supply, navigation etc.

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13 TOO MUCH WATER: PROBLEMS AND SOLUTIONS FLOODS: ¨ Heavy rain or rapid melting of snow is the major cause of natural flooding by streams. - This causes water in a stream to overflow its normal channel and flood the adjacent area called a flood plain. - Flood plains have fertile soil, ample water for irrigation, availability of nearby rivers for transportation and recreation, flatlands suitable for crops, buildings, highways and rail roads. - In United States, 10 million households and businesses with property valued at $ 1 trillion are located in flood prone areas. - Floods are a natural phenomenon and have many benefits and disadvantages.

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14 Floods (Contd…) They provide the world’s most productive farmlands. - Recharge groundwater and help refill wetlands. - Kill thousands of people and cause tens of billions of dollars in property damage. - Between 1985-2001 floods killed about 3,00,000 people, 96% of them in developing countries. - Floods have been a regular feature of some parts of India and Bangladesh causing huge economic loss as well as loss of life. - Since 1960’s human activities have contributed to the sharp rise in flood deaths & damages. Deforestations, overgrazing, rapid industrialization & global warming have contributed largely to floods.

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15 METHODS TO REDUCE FLOOD RISKS: ¨ To straighten & deepen streams – a process called channelization. - It can reduced upstream flooding but it removes bank vegetation & increases stream velocity which can promote upstream bank erosion, increase downstream flooding and sediment deposition & reduce habitats for aquatic wildlife. ¨ To build levees which contain & speed up stream flow. - Don’t protect against unusual & powerful floodwater as accrued in 1993 when two third of the levees built along the Mississippi river were damaged or destroyed. ¨ Building Dams ¨ A flood control dam built across a stream or river can reduce flooding by storing water in a reservoir & releasing it gradually. ¨ India has the distinction of having the largest number of river valley projects. ¨ Dams have a number of advantages & disadvantages.

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16 Advantages - They can keep in checking floods & famines - Generate electricity & reduce water & power shortage - Provide irrigation water to lower areas - Provide water to remote areas - Promote navigation, fishery etc. Disadvantages Impacts both at upstream as well as downstream levels. - Displacement of tribal people - Loss of forests, flora & fauna - Siltation & sedimentation of reservoirs - Water logging & salinity due to over irrigation Flash floods -      Breeding of vectors & spread of vector borne diseases In comparison to big dams, there is shift towards construction of small dams or mini Hydel projects.

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17 TOO LITTLE WATER: DROUGHTS - When annual rainfall is below normal & less than evaporation, drought occurs. - About 80 countries in the world lie in arid & semi arid regions facing drought conditions. - Drought is due to several anthropogenic causes like overgrazing, deforestation, mining, intensive cropping patterns, increased exploitation of scarce water resources to get higher productivity. - Social forestry & wasteland development can check the drought to some extent.

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18 WATER MANAGEMENT In irrigation: Agricultural water consumption is 70% of the total. ¨ Lining canals bringing water to irrigation ditches ¨ Minimize percolation & evaporation loss of water - Irrigating at night to reduce evaporation ¨ Using soil & satellite sensors & computer systems to monitor soil moisture & add water only when necessary ¨ Sprinkler irrigation ¨ Use drip irrigation ¨ Polyculture ¨ Growing water efficient crops using drought-resistant & salt-tolerant crop varieties. ¨ Irrigating with treated urban waste water

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19 In Industries - Industrial water consumption – 25% of total. - Efficient and conservative use (eliminating leaks and wastages, minimizing need, efficient use in industries - setting water intake/consumption standards for industries) - Redesign manufacturing processes - Recycling and reuse - Charging for the water and waste-water services.

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20 Municipal water management Municipal water consumption is 10% of the total - Raise water prices - Use water meters and charge for all municipal water use (may reduce consumption by 10-30%) - Curbing water losses in the distribution system (finding and fixing water leaks) - Collect and reuse household water to irrigate lawns and non-edible plants. - Public outreach – educating & making people aware of · Need for conservative & efficient use of water. · Approaches for conservative & efficient use of water - Practicing Xeriscaping- replacing green lawns in arid and semi-arid regions with vegetation adapted to a dry climate. Reduces water use by 30-80 %.