The Atlas of Water. Maggie Black

Seawater Greenhouse Ltd ; Fluoride filter: India Natural Resources Economics and Management (INREM) Foundation; 93 Right2Water; www.worldforum.org; 94 World Bank flickr library; 96 US Geological Survey; 97 Prill Mediendesign & Fotografie/iStockphoto; 98 Armenia: Global Environment Facility Small Grant’s Facility; Cameroon: Global Water Partnership; 99 Marco Betti / Water Aid; 100 Peter Jeffreys/Shutterstock We have made every effort to obtain permission for the use of copyright material. If there are any omissions, we apologize and shall be pleased to make appropriate acknowledgement in any future edition.

      15

      Glossary

      aquifer – a natural underground layer, often of sand or gravel, that contains water; some aquifers are very deep and in hard rock, and have taken millions of years to accumulate their supply. billion – a thousand million. blue water – water withdrawn from lakes, rivers and aquifers for irrigation. brackish water – water that is neither fresh nor salt. consumptive use – water that is used in, for example, manufacturing, agriculture and food, which is not therefore returned to a water resource. It excludes evaporation, which eventually returns to earth as rain. desalination – the changing of salt or brackish water into fresh water; see also reverse osmosis. evaporation – the process of liquid water becoming water vapour, including vaporization from water surfaces, land surfaces, and snow fields, but not from leaf surfaces. evapotranspiration – both evaporation and transpiration (the process by which water is evaporated from a plant surface, such as leaf pores). fresh water – water that contains fewer than 1,000 milligrams per litre of dissolved solids. green water – rain water, in the context of agriculture groundwater – water that lies deep underground in aquifers. Normally free of contamination, it is regarded as a safe source of drinking water. impoundment – control of water by dam or embankment to prevent water from flowing along its natural course. improved sanitation – toilet facilities that hygienically separate human excreta from human contact. These include “wet” systems, where water in a U-shaped pipe creates a seal, and which may be connected to a sewer or septic tank, and “dry” systems such as a pit toilet with a cleanable squat plate, cover and solidly constructed pit. Sanitation is considered adequate if it can effectively prevent human, animal and insect contact with faeces; this excludes public toilets in most settings. improved water source – a water source with protection from contamination, such as a household connection to a safe piped supply or a public standpipe similarly connected; a borehole or protected well; a covered spring or rainwater collection system. internal renewable water resources – average annual flow of rivers and recharge of groundwater generated from precipitation falling within the country’s borders. leaching – the process by which soluble materials in the soil, such as salts, nutrients, pesticide chemicals or contaminants, are washed into a lower layer of soil, or are dissolved and carried away by water. melt-water – water produced by the melting of snow or ice. precipitation – rain, snow, hail, sleet, dew, and frost. renewable resources – total resources offered by the average annual natural inflow and run-off that feed a catchment area or aquifer; natural resources that, after exploitation, can return to their previous stock levels by the natural processes of growth or replenishment. reverse osmosis – a desalination process that uses a semi-permeable membrane to separate and remove dissolved solids, viruses, bacteria and other matter from water; salt or brackish water is forced across a membrane, leaving the impurities behind and creating fresh water. river basin – the area of land drained by a river and its tributaries. A basin is considered “closed” when its water is over-committed to human uses, and “closing” when it is approaching that state. run-off – the movement of rain water over ground. salt water – water that contains significant amounts of dissolved solids. sewerage – a system of pipes with household connections to larger receptor and interceptor pipes and tunnels, that carries off waste matter, either to a treatment plant or directly to a river or stream. surface water – water pumped from sources open to the atmosphere, such as rivers, lakes, and reservoirs. unimproved water source – vendor, tanker trucks, and unprotected wells and springs. wastewater treatment – the process of turning contaminated water into water that can be re-used for a range of purposes, depending on the level to which it has been treated. water table – the upper level of groundwater in soil. withdrawal – water removed from groundwater or surface water for use.

      16

      Useful Conversions

      1 cubic metre (m3) = 1,000 litres 1 cubic kilometre (km3) = 1,000,000,000 cubic metres (m3) = 1,000,000,000,000 litres 1 litre = 0.264 US gallons (liquid) = 0.219 UK gallons 1 US gallon (liquid) = 3.785 litres 1 UK gallon = 4.55 litres 1 cubic metre (m3) = 264.172 US gallons (liquid) = 219.9 UK gallons 1 US gallon (liquid) = 0.00378 cubic metres = 3,785 cubic centimetres (cc) 1 UK gallon = 0.00454 cubic metres = 4,546 cubic centimetres (cc) 1 cubic kilometre (km3) = 810,713 acre feet 1 acre foot = 1,233 cubic metres (m3) = 325,851 US gallons (liquid) 1 kilometre (km) = 0.621 miles 1 mile = 1.6 kilometres (km) 1 kilogram (kg) = 2.2 pounds (lb) 1 pound (lb) = 0.45 kilograms (kg) = 450 grams (g) Metric water–weight conversion 1 kilogram (kg) of water = 1 litre of water 1 gram of water = 1 cubic centimetre (cc) of water 1 metric tonne (mt) of water = 1,000 kilogram (kg) of water = 1,000 litres of water = 1 cubic metre (m3)

      17

      Part 1

      A Finite Resource

      Water, fundamental to all life and human activity, is under serious threat. This is not because the supply is dwindling significantly – although some aquifers containing irreplaceable fossil water are being exhausted. The renewable supply of water on which planetary survival and well-being depend remains constant. Moisture evaporated by the sun from seas, soil and vegetation is released as rain to nourish plant growth and fill rivers, lakes and underground aquifers. Climate change may be influencing the localized behaviour and impacts of this “hydrological cycle”, but this is not the most immediate threat. Water falls unevenly in different latitudes and terrains, but there ought to be enough to meet humanity’s needs. The problem lies in the way its consumption per head has been rising much faster than population growth. An increasing number of people with industrialized lifestyles consume diets rich in foodstuffs needing extra water to produce, and demand goods such as cars, television sets and computers whose manufacture also requires large volumes of water. This places excessive demands on vulnerable sources, stretching the available supply to its physical limits – especially in less well-endowed regions such as the Middle East. The ability to control water and manage its use for productive purposes has always been central to human and economic development. Leaders of the ancient world depended on hydraulic works – dams, lifting devices and artificial lakes – to develop and maintain their civilizations. They fully understood the variability of rainfall and run-off that constituted the universal freshwater problem, long before today’s pressures had to be taken into account. Those living in water-short areas or those with seasonal rains tackle their problems by capturing run-off behind dams, and storing or diverting water for agricultural or other uses. As more water is manipulated in this way, the environmental and other limits of this approach have become apparent. Upstream and downstream users of the same resource, in river basins and watersheds, are forced into dispute as populations grow and demands increase. However unevenly distributed, the supplies provided by natural forces are going to have to suffice. New ways of managing water will have to be found in order to maintain quantity and quality and achieve a fair distribution of a substance essential to life on Earth.

      19

      The volume of water in the world never changes, but only 2.5 per cent is fresh. More than two-thirds of fresh water is locked up in polar ice-caps and permanent snow cover. Of the rest, a small proportion is in lakes and streams, and the rest in underground aquifers. Working in tandem, salt and fresh waters power life on Earth by a dynamic and constantly regenerative process. The sun’s heat evaporates water from seas and lakes, and moisture in vegetation is absorbed into the air through evapotranspiration. Once in the atmosphere, water vapour condenses into droplets. Clouds form from which

      rain and snow are released. This replenishes rivers and aquifers, enabling them to nourish soil fertility and promote plant growth. The “hydrological cycle” depicts the forces energizing and controlling the movement of water