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A unit hydrograph (UH) is the hypothetical unit response of a watershed (in terms of runoff volume and timing) to a unit input of rainfall. It can be defined as the direct runoff hydrograph (DRH) resulting from one unit (e.g., one cm or one inch) of effective rainfall occurring uniformly over that watershed at a uniform rate over a unit period ...
Computing the total hydrograph Provided the value of A is known, the total hydrograph can be obtained using a successive number of time steps and computing, with the runoff equation, the runoff at the end of each time step from the runoff at the end of the previous time step. Unit hydrograph The discharge may also be expressed as: Q = − dS/dT .
Building on the work of Horton, the unit hydrograph theory was developed by Dooge in 1959. [18] It required the presence of the National Environmental Policy Act and kindred other national legislation to provide the impetus to integrate water chemistry to hydrology model protocols.
The SWMM 5.0.001 to 5.1.022 main components are rain gages, watersheds, LID controls or BMP features such as Wet and Dry Ponds, nodes, links, pollutants, landuses, time patterns, curves, time series, controls, transects, aquifers, unit hydrographs, snowmelt and shapes (Table 3). Other related objects are the types of Nodes and the Link Shapes.
Todini initiated his research career dealing with hydrological models. Initially he proposed a Quadratic Programming alternative to the constrained estimation of Unit Hydrographs as an alternative to the Linear Programming approach proposed by Eagleson. [13] The work was based on the seminal work of Norbert Wiener and Norman Levinson. [14]
A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or conduit carrying flow. The rate of flow is typically expressed in units of cubic meters per second (m³/s) or cubic feet per second (cfs). Hydrographs often relate changes of precipitation to changes in discharge over time. [3]
The runoff curve number is based on the area's hydrologic soil group, land use, treatment and hydrologic condition.References, such as from USDA [1] indicate the runoff curve numbers for characteristic land cover descriptions and a hydrologic soil group.
A hydrologic model is a simplification of a real-world system (e.g., surface water, soil water, wetland, groundwater, estuary) that aids in understanding, predicting, and managing water resources.