1 Hydrology Hydrology is a branch of Earth

� 1 - Hydrology �Hydrology is a branch of Earth Science, and it deals with water science in terms of its distribution over the ground surface and in the atmosphere. Its mainly the oceans and seas, rivers and all rainfall types (rain and snow, and…. . ) in addition to groundwater. �And this science is divided into two sections: � 1. Scientific Hydrology: dealing with theoretical studies. � 2. Engineering Hydrology (Applied): that deal with engineering studies.

�To estimation of water resources: �Study processes such as rainfall and total runoff and evaporation and their interaction. �Study problems such as flooding and drought ( )ﺟﻔﺎﻑ and shielding strategy.

1. 2 HYDROLOGIC CYCLE �The movement of water in all its forms (rain and snow and Glaze…. . ) between the earth's surface to the atmosphere, where : � 1. The water is evaporated by the heat of the sun and then moves to the atmosphere. � 2. The evaporated water condenses to come down again to the oceans and seas as rain or wind may carry the clouds to land to fall to the earth's surface. � 3. Water ways like rivers and streams or fall as snow or cold has been infiltrating a large portion of it to the underground so-called groundwater.

1 -3 Hydrological cycle Paths: �In general and the simplified hydrological cycle paths are: - �Rainfall �Evaporation � Infiltration �Runoff surface � Groundwater �Although each track of these routes include one or more of the following : �a. Water transfer �b. Temporary storage of water

1. 4 Hydrological Budget Equation ) ﻣﻌﺎﺩﻟﺔ ﺍﻟﻤﻮﺍﺯﻧﺔ ﺍﻟﻬﻴﺪﺭﻭﻟﻮﺟﻴﺔ : �The hydrologic equation is simply the statement during the period of time (Δt) and is given by : - �I = O + ΔS. . . (1. 1) �where I = inflow �O = outflow �ΔS = change in storage �ΔS = Vi - Vo �This equation states that during a given period, the total inflow into a given area must equal the total outflow from the area plus the change is storage.

�While solving this equation, the ground water is considered as an integral part of the surface water. �Example / � Basin area of 15 km 2, calculate the change in the storage (for one year) above the earth and under these basin if the volume of water to flow inside 8 * 104 m 3 and the out flow 6. 5 * 104 m 3 If the annual rate of flow of the waterway is 107 m 3 calculate the equivalent depth ? �Solution � 1. ΔS = Vi – Vo � ΔS = 8 * 104 – 6. 5 * 104 = 1. 5 * 104 m 3 �Average Depth = 107 / 15*106 = 0. 667 m. = 66. 7 cm.

SCOPE OF HYDROLOGY �The study of hydrology helps us to know : �(i) the maximum probable flood that may occur at a given site and its frequency; this is required for the safe design of drains and culverts, dams �(ii) the water of a basin—its occurrence, quantity and frequency, etc. this is necessary for the design of dams, water supply, water powered. �(iii) the ground water development for which a knowledge of the hydro-geology of the area

�(iv) the maximum intensity of rain-storm and its frequency for the design of a drainage project in the area. �For the analysis and design of any hydrologic project, the basic hydrological data required are: �(i) Hydro-meteorological data like temperature, wind velocity, humidity, etc. �(iii) rainfall records �(iv) Stream-flow records

�(v) piezo-metric heads of ground water table �(vi) Evaporation data �(vii) Water quality data of surface streams and ground water