Introduction to Hydrology

CE 217- HYDROLOGY • Hydrology – Hudor - “water”; Logy - “study of” – Study of water (occurrence, circulation, and distribution) and its behavior in the environment. • Water Management – Sustainable use of water resources – Manipulating the hydrologic cycle • Hydraulic structures, water supply, water treatment, wastewater treatment & disposal, irrigation, hydropower generation, flood control, etc.

Global Water Resources

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Global Water Withdrawal & Consumption

Global Water Use

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Global Water Cycle

Schematic Diagram of Hydrologic Cycle

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Hydrologic Cycle Hydrologic Cycle is the constant cyclic movement of water from the ground to the atmosphere and back to the ground Components Hydrologic Cycle •

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Evaporation. The process by which liquid water is converted into water vapor as water is heated by the sun and it's surface molecules become sufficiently energized to break free of the attractive force binding them together. Transpiration. The process by which water vapor is emitted into the atmosphere from plant surfaces. Evapotranspiration is the combination of water released to the atmosphere by evaporation and transpiration. Condensation. The process by which water vapor condenses back into liquid after it rises and cools in the atmosphere. When condensation occurs at the ground level, the resulting water droplets are called dew. Precipitation. The discharge of water out of the atmosphere, generally onto land or water surface. It is also commonly used to designate the quantity of water that is precipitated and is the primary input quantity to the hydrologic cycle.

Interception. The process by which precipitation is caught and held by foliage, twigs, and branches of trees, shrubs, and other vegetation, and lost by evaporation, never reaching the surface of the ground. Infiltration. The movement of water through the soil surface into the soil which is controlled by soil texture, soil structure, vegetation and soil moisture status. Surface Runoff. The portion of water which does not infiltrate the soil but flows over the surface of the ground to a stream channel. Surface runoff is also known as overland flow. Percolation. Precipitation that moves downwards, percolates or infiltrates through cracks, joints and pores in soil and rocks until it reaches the water table where it becomes groundwater. Interflow. Lateral movement of percolated water. Some water that is precipitated seeps through soil and continues to follow the slope. This water is eventually discharged into rivers, streams, and lakes. Groundwater Flow. A body of water found in a deep aquifer zone that flows laterally and eventually merges with rivers, streams, lakes, and oceans.

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