Hydrology module one for Civil engineers

hydrology for engineers

1. HYDROLOGY CEPC 9

2. Hydrology and Hydrologic Cycle Module 1, Lesson 1

3. What is the difference between HYDROLOGY and HYDRAULICS? What is HYDROLOGIC CYCLE?

4. Hydrology is defined as the circulation of water and its constituents through the hydrologic cycle, or the quantification of flows that are ultimately produced by precipitation. It deals with precipitation (rain, snow, sleet, hail, etc.), evaporation, infiltration, groundwater flow, surface runoff, streamflow , and the transport of substances dissolved or suspended in flowing water. Hydraulics is defined as the study of the mechanical behavior of water in physical systems. In engineering terms, hydraulics is the analysis of how surface, and/or subsurface flows move from one point to the next. Hydraulic analysis is used to evaluate flow in rivers, streams, storm drain networks, water aqueducts, water lines, sewers, etc.

5. The Hydrologic Cycle is a conceptual model that described the storage, movement of water and sequence of conditions through which water passes or circulates on and below the earth’s surface and the atmosphere.

6. Interrelationships of Phases of Hydrologic Cycle Evaporation It is the process in which liquid changes to gas Evapotranspiration It is the combined net effect of evaporation and transpiration. It is also the combination of water released to the atmosphere by evaporation and transpiration. Transpiration It is the process by which plants return moisture to the air. Plants take u p water through their roots and loses some of the water through pores in their leaves. As hot air passes over the surface of the leaves, the moisture absorbs the heat and evaporates into the air.

7. Interrelationships of Phases of Hydrologic Cycle Condensation It is the cooling of water vapor until it becomes liquid Precipitation The moisture that falls from the atmosphere as rain, snow, sleet or hail Interception Refers to the precipitation that does not reach the soil, but is instead intercepted by the leaves, branches of plants and and the forest floor. It occurs in the canopy, and in the forest floor or litter layer. Sublimation It is the conversion of solid phase to gaseous phase without passing the liquid phase. It is most often used to describe the process of snow and ice changing into water vapor in the air without first melting into water.

8. Interrelationships of Phases of Hydrologic Cycle Runoff Is the movement of water, usually from precipitation, across the earth’s surface towards stream channels, lakes, oceans or depressions or low points of the earth’s surface. 2 Kinds of Runoff 1. Surface Runoff Is the water from rain, snowmelt , or other sources that flows over the land surface. 2. Subsurface Runoff It is the flow of water beneath the earth’s surface.

9. Interrelationships of Phases of Hydrologic Cycle Transport It is the movement of water through the atmosphere, specifically from over the oceans to over land. Infiltration and Percolation Infiltration It is the entry of water into the soil surface Percolation I t is the downward movement of water trough soil and rocks

10. Human Processes that affect the W ater Cycle Storage of water in reservoir M ining Irrigation Urbanization Combustion Deforestation

11. Storage of water in Reservoir A reservoir is a storage space for liquids. By building dams and reservoirs, water will be stored and therefore less water will flow over the surface and through underground stores, back to the river. This can result in a lowering of the water table. They can also have an impact on where it rains. Dams and reservoirs increase evaporation, resulting in increased cloud formation in these areas. Cloud formation would therefore be altered, changing levels of precipitation.

12. Mining Mining is the extraction of minerals or other geological materials from the earth. The extraction of ores and minerals. This involves removing vegetation, then digging or blowing large holes in the ground . Mining will cause the silting up of lakes, reservoirs and rivers reducing the amount of storage in these areas. It may also result in a reduced vegetation cover, leading to increased runoff and evapotranspiration.

13. Irrigation Irrigation is the application of controlled amounts of water to plants needed interval. This takes water from the natural source and can cause leaching and runoff. This is a huge human-made impact in the hydrological cycle, and thus on climate change. As we demand for more food for more people, we need more water, and irrigation is used globally to substitute for insufficient rainfall for crops. The removal of nutrients forces farmers to use more fertilizers which contaminates the water supply

14. Combustion combustion is a chemical process in which fuel reacts with oxidant to give out heat. The release of heat can produce light in a form of flame. The increasing use of fossil fuels raises the earth’s temperature through gases better trapping infrared radiation, thus increasing evaporation, and the melting of ice.

15. Deforestation Deforestation is the t he cutting down or burning of trees. It increases the amount of runoff water and it decreases evapotranspiration , therefore decreasing cloud formation. As there are no longer tree roots to take up ground water or leaves to intercept precipitation, this leads to more extreme river flows and the areas can be more susceptible to drought and flooding.

16. Urbanization Urbanization is the expansion of towns and cities. This will reduce the amount of natural vegetation available and replace it with impermeable surfaces and drains. This will increase surface runoff and also evaporation, leading to higher river levels. It will also reduce the water table as less water is being returned to underground stores .

17. What is a WATERSHED? A watershed is the land area that drains water to a particular stream, river, estuary or bay. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map.

18. What is WATERSHED DELINEATION and its importance? Watershed Delineation is the process of identifying the drainage area of a point or set of points. It is also drawing or plotting lines to a map to identify watershed’s boundaries. Watershed delineation is important since it provides better understanding of hydrologic relationships. It also helps us develop a better understanding of how climate affects water supply, and allows us to make rational planning and management decisions.

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