Course Water Resource Evaluation PDF
1.Introduction:
Water is used for a variety of purposes, and these have very different quantity, quality, and timing characteristics. It is a fundamental natural resource that influences human health, ecology and economic development. Man requires it for his cooking, washing, sanitation, drinking and for growing his crops and running his factories. Man has used water to generate hydropower or regulate river flow; extensive groundwater schemes have also been linked to complex multi-source centralised public water supply systems in some countries. Water has also been used for waste disposal and irrigated agriculture. Demands for water, has however fluctuated from year to year depending on the weather patterns. It is therefore important to discuss how this delicate resource is studied, managed and evaluated to sustain its usefulness.
Course Water Resource Evaluation PDF
Water Science, hydrology or in general terms, water study is an applied science, borrowing from engineering, pure and physical science, social sciences and management. Its study therefore requires a sound, broad based education in these areas. The present course structure however employs a beginner’s approach to the study of water resource management and evaluation. There are two Modules (2) in this course, each with six units (6). The approach is the system form that makes use of the variables in water cycle for its explanations, in order to lead you through a clearly defined pathway of the water cycle system, and the way each is evaluated.
Unit 1 introduces you to the nature and distribution of water on the earth.
Unit 2 explains the concepts of hydrological or water cycle. It provides information about how water cycling occurs through the processes of evaporation, condensation, precipitation, runoff, to groundwater flow and the processes involved.
Units 3 to 5 describe the processes involved in water cycle to some level of details, the reservoirs; particularly the surface and subsurface sources. The concept of the unit of hydrological measurements, drainage basin is discussed in unit 6.
The Units 1 to 5 of Module 2 focused on the discussion of the precipitation, evaporation, runoff and stream flow, in that order. Techniques for obtaining information about these variables were also highlighted.
Finally, water quality in the surface and subsurface basins forms the basis of discussion in Unit 6. Pollution and the regulating framework for water management in some parts of the world, including Nigeria are also discussed here.
2.The Course:
This Course Guide tells you briefly what to expect from this material. The study of Water is not only an academic endeavour, it is a lifelong determining process. Where is Earth's water located and in what forms does it exist? Is it safe for drinking? Can fish and other aquatic life thrive in streams and lakes that are affected by human activities? What is the water quality? All these are questions that are relevant to human survival on earth.
Hydrology is the science that studies the Earth's water molecules and their movement through the hydrologic cycle. The Earth and its various abiotic and biotic systems are greatly influence by water. Water is essential for life and plays an important role in atmospheric and lithospheric processes.
The hydrologic cycle is used to model the storage and movement of water molecules between the biosphere, atmosphere, lithosphere and hydrosphere. Water is stored in the following reservoirs: atmosphere, oceans, lakes, rivers, glaciers, soils, snowfields, and groundwater. It moves from one reservoir to another by processes like: evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, and groundwater flow.
Precipitation can be defined as any aqueous deposit, in liquid or solid form, that develops in a saturated atmospheric environment and generally falls from clouds. A number of different precipitation types have been classified by meteorologists including rain, freezing rain, snow, ice pellets, snow pellets, and hail. Fog represents the saturation of air near the ground surface. Classification of fog types is accomplished by the identification of the mechanism that caused the air to become saturated.
The distribution of precipitation on the Earth's surface is generally controlled by the absence or presence of mechanisms that lift air masses to cause saturation. It is also controlled by the amount of water vapor held in the air, which is a function of air temperature. A figure is presented that illustrates global precipitation patterns.
Evaporation and transpiration are the two processes that move water from the Earth’s surface to its atmosphere. Evaporation is movement of free water to the atmosphere as a gas. It requires large amounts of energy. Transpiration is the movement of water through a plant to the atmosphere. Scientists use the term evapotranspiration to describe both processes. In general, the following four factors control the amount of water entering the atmosphere via these two processes: energy availability; the humidity gradient away from the evaporating surface; the wind speed immediately above the surface; and water availability. Agricultural scientists sometimes refer to two types of evapotranspiration: Actual Evapotranspiration and Potential Evapotranspiration. The growth of crops is a function of water supply. If crops experience drought, yields are reduced. Irrigation can supply crops with supplemental water. By determining both actual evapotranspiration and potential evapotranspiration a farmer can calculate the irrigation water needs of their crops.
The distribution of precipitation falling on the ground surface can be modified by the presence of vegetation. Vegetation in general, changes this distribution because of the fact that it intercepts some the falling rain. How much is intercepted is a function of the branching structure and leaf density of the vegetation. Some of the water that is intercepted never makes it to the ground surface. Instead, it evaporates from the vegetation surface directly back to the atmosphere. A portion of the intercepted water can travel from the leaves to the branches and then flow down to the ground via the plant’s stem. This phenomenon is called stemflow. Another portion of the precipitation may flow along the edge of the plant canopy to cause canopy drip. Both of the processes described above can increase the concentration of the water added to the soil at the base of the stem and around the edge of the plant’s canopy. Rain that falls through the vegetation, without being intercepted, is called throughfall.