Big Picture
The circulation of Earth's water.
Low lands adjoining a river, stream, lake, or bay that may have been or may be inundated by flood water.
What is a floodplain?
Rain, snow, sleet, hail.
What is precipitation?
Graph showing how the runoff at a point of interest varies with time.
What is a hydrograph?
The land area that contributes to flow at a point of interest. Often serves as the boundary for hydrologic model development.
What is a watershed?
A method for accounting for water quantities present in various components of the hydrologic cycle.
What is a hydrologic budget?
The average number of years between occurrences of a hydrologic event with a certain magnitude or greater.
What is a return period (or recurrence interval)?
Process of water entering the soil.
What is infiltration?
Portion of flow in a hydrograph representing the groundwater contribution.
What is baseflow?
A hypothetical storm event that is used in predicting the hydrologic response of a watershed.
What is a design storm?
A science dealing with the properties, distribution, and circulation of the Earth's water.
What is hydrology?
A method to determine the flood discharge magnitudes that correspond to return periods.
What is flood frequency analysis?
Water changing from liquid to gas phase from soil, open water, vegetation.
What is evapotranspiration?
Time that it takes for a drop of runoff to reach a point of interest from the hydrologically most distant point in the watershed.
What is the time of concentration?
A value representing the hydrologic soil group, land use, and antecedent moisture condition of a watershed.
What is a Curve Number (CN)?
A branch of engineering that applies fluid mechanics principles to problems dealing with the collection, storage, control, transport, regulation, measurement, and use of water.
What is hydraulics?
A probability distribution recommended by the U.S. Water Council to be used in flood analysis.
What is the log Pearson type III distribution?
Water that goes from the gas phase to liquid phase.
What is condensation?
A hydrograph resulting from 1 in (or 1 cm) of runoff from a watershed.
What is a unit hydrograph?
A method to compute the peak discharge for small ungaged watersheds (up to 200-300 acres).
What is the Rational Method?
A process which promotes the coordinated development and management of water and related resources in order to maximize economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems.
What is Integrated Water Resources Management (IWRM)?
A year designated to start October 1 and end on September 30.
What is a water year?
Water that is prevented from reaching the ground.
What is interception?
Process of moving a hydrograph from one location to another and accounting for differences in timing and storage that occur over a distance.
What is hydrograph routing?
Curves that are determined on a regional basis from frequency analysis of precipitation data. These are often used to create a hypothetical storm event.
What are intensity-duration-frequency (IDF) curves?