CHAPTER ONE
INTRODUCTION
1.1BACKGROUND OF THE STUDY
Water is one of the world's most valuable resources. It is a basic necessity of life for both plants and animals. Mankind cannot, in fact, survive without water as even the human body is made up of about 70% water.Water resources are becoming increasingly scarce in many parts of the world due to development, increased demand, climate change and resulting drought and explosive population growth. The availability of a reliable and clean supply of water is one of the most important determinants of our health. WHO explains that diseases related to drinking-water contamination represent a major burden on human health and the interventions to improve the quality of drinking-water provide significant benefits to health.
Water is the only substance that exists naturally on Earth in all three physical states of matter, gas, liquid, and solid, and it is always on the move among them. The Earth has oceans of liquid water and Polar Regions covered by solid water. Energy from the sun is absorbed by liquid water in oceans, lakes, and rivers and gains enough energy for some of it to evaporate and enter the atmosphere as an invisible gas, water vapour. As the water vapour rises in the atmosphere it cools and condenses into tiny liquid droplets that scatter light and become visible as clouds. Under the proper conditions, these droplets further combine and become heavy enough to precipitate (fall out) as drops of liquid or, or if the air is cold enough, flakes of solid, thus returning to the surface of the Earth to continue this cycle of water between its condensed and vapour phases..
The hydrologic cycle is a conceptual model that describes the storage and movement of water between the biosphere, athmosphere, lithosphere, and the hydrosphere. Water on our planet can be stored in any one of the following major reservoirs: atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and groundwater. Water moves from one reservoir to another by way of processes like evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, melting and groundwater flow. The oceans supply most of the evaporated water found in the atmosphere. Of this evaporated water, only 91% of it is returned to the oceans basins by way of precipitation. The remaining 9% is transported to areas over landmasses where climatological factors induce the formation of precipitation. The resulting imbalance between rates of evaporation and precipitation over land and ocean is corrected by runoff and groundwater flow to the oceans.
Water resources are becoming increasingly scarce in many parts of the world due to development, increased demand, climate change and resulting drought and explosive population growth. The availability of a reliable and clean supply of water is one of the most important determinants of our health. Thus, water use (demand) is a function of availability (supply).
Water use falls into several major classes, each of which is associated with certain quantity and quality requirements. These classes include water for drinking and cooking, waste disposal, crop production, aquaculture, livestock, industrial use, recreational use, navigational use, and ecological values such as survival of natural lake, riverine or wetland communities. The quantity of water used within each of these classes is influenced mainly by variables such as climate and precipitation. The proportion of total water used for any specific purpose is controlled by socioeconomic conditions, tradition, culture and water availability. Agriculture based economies, such as Nigeria's, shall require up to 80% of available water for agriculture, and 10% each for industrial and domestic purposes.
In an urban setting, the water used to generate electricity may be used for irrigation down a river. The same water might be used yet again as it is withdrawn for a public water supply or an industry. Only a few uses actually consume water. Irrigated agriculture, for example, consumes 55% of the water it uses. The consumptive nature of irrigation, therefore, limits many simultaneous users of the same resource. Municipal facilities such as cities consume 21% of water they withdraw. In contrast, industry which withdraws very large quantities of water, consumes only about 3% of that water. Although the quality of water returned to the system may change. Unless unacceptable changes in quality occur, many industrial users could benefit from the same water resource. The human needs about 2-10 litres of water per day for normal physiological functions, depending on climate and workload. About 1 litre of water is provided by daily food consumption. The total water consumption per capita per day is determined by a number of factors, such as availability, quality, cost, income, size of family, cultural habits, standard of living, ways and means of water distribution and climate (World Bank Water Research Team, 1993).