Hydrology.docx

HYDROLOGY HYDRO = WATER LOGY = SCIENCE -

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is the science that encompasses the occurrence, distribution, movement and properties of the waters of the earth and their relationship with the environment within each phase of the hydrologic cycle. Water is one of our most precious natural resources, without it, there would be no life on earth. Has evolved as a science in response to the need to understand the complex water system of the earth and help solve water problems. This hydrology primer gives you information about water on earth and human’s involvement and use of water.

Stages of Water Cycle 1. EVAPORATION - Water is transferred from the surface to the atmosphere. - Through evaporation, the process by which water changes from a liquid to a gas. The sun’s hear provides energy to evaporate water from the earth’s surface. Land, lakes, rivers and oceans send up a steady stream of water, vapor and plants also lose water to the air (transpiration)

2. Transport - The movement of water through the atmosphere, specifically from over the oceans to over land. - Some of the earth’s moisture transport is visible as clouds, which themselves consist of ice crystals and/or tiny water droplets.

3. Condensation - The transported water vapor eventually condenses, forming tiny droplets in clouds

4. Precipitation - The primary mechanism for transporting water from the atmosphere to the surface of the earth - When the clouds meet cool are over land, precipitation, in the form of rain, sleet or snow, is triggered and water returns to the land or sea, a proportion of atmospheric precipitation evaporates.

5. Groundwater - Some of the precipitation soaks into the ground and this is the main source of the formation of the waters found on land, rivers, lakes, groundwater and glaciers.

6. Run-of - Most of the water which returns to land flows downhill. - Some of it penetrates while the rest, as river flow, returns to the oceans where it evaporates. - As the amount of groundwater increases or decreases, the water table rises falls accordingly. - Then the entire area below the ground is saturated, flooding occurs because all subsequent precipitation is forced to remain on the surface.

HISTORY OF HYDROLOGY 

Irrigation canal - Egypt

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King Scorpion 3200 B.C.

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Diversion canal - King Menes - 3000 B.C.

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Sadd el-Kafara Dam - 28550 B.C.

WHAT DO HYDROLOGIST DO?    

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They apply scientific knowledge and mathematical principles to solve water-related problems in society: problems of quantity, quality and availability. They may be concerned with finding water supplies for cities or irrigated farms, or controlling river flooding or soil erosion. They may work in environmental protection preventing or cleaning up pollution or locating sites for safe disposal of hazardous wastes. Much of their work relies on computers for organizing, summarizing and analyzing masses of data, and for modelling studies such as the prediction of flooding and the consequences of reservoir releases or the effect of leaking underground oil storage tanks. The work of hydrologists is as varied as the uses of water and may range from planning multimillion dollar interstate water projects to advising homeowners about backyard drainage problems.

1. Surface Water - Hydrologists help cities by collecting and analyzing the data needed to predict how much water is available from local supplies and whether it will be sufficient to meet the city’s projected future needs. - Hydrologic and water quality mathematical models are developed and used by hydrologists for planning and management and predicting water quality effects of changes conditions.

2. Ground Water - Hydrologists estimate the volume of water stored underground by measuring water levels in local wells and by examining geologic records from will-drilling to determine the extent, depth and thickness of water-bearing sediments and rocks.

WEATHER AND HYDROLOGY The hydrologic characteristics of a region are determined largely by its geology and geography, climate playing a dominant part. Climate Factors: a. b. c. d.

Amount and distribution of precipitation Occurrence of snow and ice Efects of the wind Temperature and humility on evapotranspiration and ice melt

MEASUREMENT OF RADIATION Actinometer & Radiometer -

Used to measure intensity of radiant energy

TYPES: 1. Pyrheliometer - Measuring intensity of direct solar radiation.

2. Pyranometer - Measuring hemisphere shortwave radiation

3. Pyrgeometer - Measuring hemisphere longwave radiation

4. Pyrradiometer (total hemispherical radiometer) - measuring all-wave radiation flux - LONGWAVE RADIATION + GLOBAL RADIATION + REFLECTED RADIATION

5. Net Pyrradiometer - Measuring nel all-wave radiation flux.