Global Water Distribution & Sources of Water.ppt
- 1. WRM 209: Water Quality Assessment and Monitoring DR. AMOS KYALO MUTUA Ph.D; Marine Biology (UoN-Kenya), M.Sc Ecological Marine Management (VUB-Belgium); B.Sc Zoology and Botany (UoN-Kenya).
- 2. Global Water Distribution • Globally, water sources are distributed as shown below.
- 3. Sources of Water; Surface water: • Surface water is precipitation that does not infiltrate into the ground or return to the atmosphere by transpiration or evaporation. • It may be loosely defined as water that stands or flows on the surface of the Earth and is commonly referred to as runoff.
- 4. Surface water • Since the spread of urbanization associated with the change from an agrarian to industrial societies, human beings have drained landscapes using essentially the same approach. • Standing water is perceived as a hazard and therefore we have tried to move the runoff, or storm water, quickly, safely and economically into sewers, and then with the same emphasis into the nearest watercourse. • However, urbanization changes the local natural hydrological cycle as the impermeable surfaces associated with development reduce infiltration and transpiration, and instead divert the precipitation into the drainage system.
- 5. Surface water: Cycle • The Figure below shows how the volume of surface runoff changes between natural and urbanized environments. •
- 6. Sources of Water • Surface water: • Examples – Rivers, lakes or fresh water wetlands. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and sub-surface seepage. – Total quantity of water in surface systems depends on storage capacity, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates.
- 7. Surface Water Cont’d • Natural surface water can be augmented (increased) by importing surface water from other watersheds through canals or pipelines. • Human beings can also cause surface water to be "lost" (i.e. become unusable) through pollution.
- 8. Sources of water • Under River flow – Water flowing through sub-surface rocks and gravels that underlie the river and its floodplain. – This region is called the hyporheic zone. – For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. – The hyporheic zone often forms a dynamic interface between surface water and true ground-water receiving water from the ground water when aquifers are fully charged and contributing water to ground-water when ground waters are depleted.
- 9. Sources of Water • Ground water – This is Sub-surface water which is fresh water located in the pore space of soil and rocks. – It is also water that is flowing or held within aquifers below the water table. – Two types • sub-surface water that is closely associated with surface water and • deep sub-surface water in an aquifer (sometimes called "fossil water").
- 10. Ground Water Cont’d • The natural input to sub-surface water is seepage from surface water. The natural outputs from sub- surface water are springs and seepage to the oceans. • If the surface water source is subject to substantial evaporation, sub-surface water source may become saline. • In coastal areas, human use of a sub-surface water may cause the direction of seepage to ocean to reverse which can also cause soil salinization. • Humans can also cause sub-surface water to be "lost" (i.e. become unusable) through pollution. • Humans can increase the input to a sub-surface water source by building reservoirs or detention ponds.
- 11. Sources of Water • Desalination – Desalination is an artificial process by which saline water (generally sea water) is converted to fresh water. The most common desalination processes are distillation and reverse osmosis. Desalination is currently expensive compared to most alternative sources of water, and only a very small fraction of total human use is satisfied by desalination. It is only economically practical for high-valued uses (such as household and industrial uses) in arid areas. The most extensive use is in the Persian Gulf e.g. Israel and Libya, and other Mediterranean and Middle East Countries.
- 12. Desalination Cont’d • Distillation: Boiling to vapour state to remove salts. Resulting water vapour is cooled to give fresh water. • Reverse osmosis (RO) is a filtration method that removes large molecules and ions from solutions by applying pressure to a solution through a selective membrane. • In the normal osmosis process the solvent naturally moves from an area of low solute concentration, through a membrane, to an area of high solute concentration. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis.
- 13. Sources of Water • Frozen water – Use of Icebergs in the polar regions and high altitudes as water sources – Glacier Run off is however considered as surface run off. – The Himalayas, contain some of the most extensive area of glaciers and permafrost outside of the poles. Ten of Asia’s largest rivers flow from there, and more than a billion people’s livelihoods depend on them. – NOTE: Global temperatures are rising more rapidly around Himalayas than the global average. In Nepal the temperature has risen with 0.6 degree over the last decade, whereas the global warming has been around 0.7 over the last hundred years.
- 14. Rain Water • Collected from roof tops and rock catchments. • Rainwater is naturally soft (unlike well water), contains almost no dissolved minerals or salts, is free of chemical treatment, and is a relatively reliable source of water for households. Rainwater collected and used on site can supplement or replace other sources of household water. • Rainwater harvesting systems is their flexibility. A system can be as simple as a whiskey barrel placed under a rain gutter down spout for watering a garden or a complex multi-tank, pumped and pressurized construction to supply residential and irrigation needs.
- 15. (2): Uses of Water • Categories of water use – Commercial water use includes fresh water for motels, hotels, restaurants, office buildings, other commercial facilities. – Domestic use includes water that is used in the home every day, including water for normal household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens.
- 16. Uses of Water • Industrial:For such purposes as processing, cleaning, transportation, dilution, and cooling in manufacturing facilities. Major water-using industries include steel, chemical, paper, and petroleum refining. • Irrigation: water is artificially applied to farms for crop production; chemical application, for the leaching of salts from the crop root zone (Rhizosphere). Nonagricultural activities include self-supplied water to irrigate public and private golf courses, parks,
- 17. Uses of Water • Livestock: water for stock animals, feed lots, dairies, fish farms, etc. Water is needed for the production of red meat, poultry, eggs, milk, and wool, and for horses, rabbits, and pets. Livestock water use only includes fresh water. • Mining: for the extraction of naturally occurring minerals; solids, such as coal and ores; liquids, such as crude petroleum; and gases, such as natural gas. The category includes quarrying, milling (such as crushing, screening, washing, and flotation), and other operations as part of mining activity.
- 18. Uses of Water • Public Supply: water withdrawn by public and private water suppliers, such as county and municipal water works, and delivered to users for domestic, commercial, and industrial purposes. • Thermoelectric Power Production: Production of electric power generated with heat. The source of the heat may be from fossil fuels, nuclear fission, or geothermal. They generate electricity by turning a turbine using steam power. • Hydroelectric Power Production: Force of water to turn turbines