Hydrology
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deals with water of the Earth
their occurrence, circulation and distribution
their chemical and physical properties
their reaction with the environment, including their relation to living things
Engineering Hydrology
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includes segments of the field pertinent to planning, design and operation of engineering
projects for the control and use of water
Hydrologic Cycle
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The precipitation which falls upon land is dispersed in several ways.
- The greater part is temporarily retained in the soil near where it falls and is ultimately
returned to the atmosphere by evaporation and transpiration by plants.
- A portion of the water finds its way over and through the surface soil to stream channels
- Other water penetrates farther into the ground to become part of the groundwater.
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Under the influence of gravity, both surface streamflow and groundwater move toward lower
elevations and may eventually discharge in the oceans.
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However, substantial quantities of surface and underground water are returned to the
atmosphere by evaporation and transpiration before reaching the oceans.
Hydrological Process
1. Condensation
- is the process by which water vapor changes its physical state from a vapor, most common
to liquid. Water vapor condenses onto small airborne particles to form dew, fog or clouds
2. Rainfall or Precipitation
- water condensing from the atmosphere and falling in drops or particles to the land
3. Runoff
- water from precipitation, snowmelt, or irrigation running over the surface of the Earth’s
surface water entering rivers, lakes, reservoirs
4. Infiltration
- is the process by which water on the ground surface enters the soil
5. Percolation
- is the movement of water though the soil, and its layers, by gravity and capillary forces. The
prime moving force of groundwater is gravity. Water that is in the zone of aeration where
air exists is called Vadose Water. Water that is in the zone of saturation is called
Groundwater.
6. Evaporation
- occurs when the physical state of water is changed from a liquid state to a gaseous state
7. Transpiration
- the biological process that occurs when water inside the plants evaporates as water vapor
through numerous individual leave openings
8. Storage/Interception
- Portion of water that are intercepted and/stored on land (in vegetation), water bodies and
underground crevices. Storage occurs in oceans, lakes, reservoirs, glaciers, underground;
surface occurs in the soil, in aquifers and in the crevices of rock formation
Examples of structures or systems that requires understanding of hydrology:
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Flood control structures
Drainage systems
Storm water management
Irrigation system
Groundwater resources system
Water resources / water supply system