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A runoff models or rainfall-runoff model describes how rainfall is converted into runoff in a drainage basin (catchment area or watershed). More precisely, it produces a surface runoff hydrograph in response to a rainfall event, represented by and input as a hyetograph. Rainfall-runoff models need to be calibrated before they can be used.
The runoff curve number (also called a curve number or simply CN) is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. [1] The curve number method was developed by the USDA Natural Resources Conservation Service , which was formerly called the Soil Conservation Service or SCS — the ...
Correspondingly, the runoff footprint allows someone to calculate their baseline annual runoff and assess what the impact of ideal stormwater green solutions would be for their site. Since the passage of the Clean Water Act in 1972, the EPA has monitored and regulated stormwater issues in urban areas. Municipalities across the United States are ...
Time of concentration is a concept used in hydrology to measure the response of a watershed to a rain event. It is defined as the time needed for water to flow from the most remote point in a watershed to the watershed outlet. [1] It is a function of the topography, geology, and land use within the watershed.
Rain harvesting systems collect runoff from rooftops and convey it to a cistern tank where it can be used for non-potable water uses and on-site infiltration. The harvesting system is assumed to consist of a given number of fixed-sized cisterns per 1000 square feet of rooftop area captured.
Conversely, the water entering a low drainage density basin will, on average, have to travel a longer distance over the low velocity hillslope to reach the channels. As a result, the water will require more time to reach the exit of the catchment.
Certain ways of managing farm fields can help the soil hold onto nutrients instead of letting them wash away. But the number of farmers who use them is a small share of the total.
Runoff routing is a procedure to calculate a surface runoff hydrograph from rainfall. Losses are removed from rainfall to determine the rainfall excess which is then converted to a hydrograph and routed through conceptual storages that represent the storage discharge behaviour of overland and channel flow. [23] [24]