Hydrological Rainfall Runoff Model


HYRROM is an easy-to-use conceptual rainfall runoff model, with no requirement to understand the computer operating system or the structure of data files. In HYRROM, flows are predicted using a simple, but realistic, representation of the physical processes which govern water flow in a catchment. Output is in the form of color screen graphics which can be sent to a plotter or graphics printer if required.
The main use of a rainfall runoff model is to predict river flows from rainfall and evaporation data. In HYRROM, flows are predicted using a simple, but realistic, representation of the physical processes which govern water flow in a catchment. The model incorporates interception, soil, ground-water and runoff stores, and includes some representation of the losses due to evapotranspiration. It can be calibrated manually or automatically using the built-in Rosenbrock optimization routine. Compatible with HYDATA.



The Rainfall Runoff Model

Rainfall, falling on a catchment is assumed to move through the catchment and to appear as a flow at the outlet. In most cases, there will be a noticeable link between the intensity of the rainfall and the magnitude of the flow it produces. This link is expressed mathematically by a set of equations within the model. The model uses the concept of 'stores' to keep account of the passage of water through the catchment. These stores can fill or empty during the simulation and provide a contribution to runoff which varies with the volume of water they contain. Four stores are used: the surface, or routing store; the interception store; the soil store; and the groundwater store. Each store influences the timing and magnitude of the flow at the outlet from the catchment. The interception and soil stores can also lose water by evaporation or transpiration.
The HYRROM parameters control the amount of flow received by, and coming from, each store for each day in the simulation. By optimizing these parameters, the model can be used to represent the relationship between catchment rainfall and runoff. A total of nine parameters can be varied by the user. They are as follows.

The SS parameter defines the size of the interception store (in millimeters depth over the catchment). The effect of this parameter is to provide a time delay between the time of rainfall and the flow of water in to the remaining stores, and hence into runoff. A large value of SS increases the time delay and, during dry periods, may prevent the remaining stores from being replenished.
Parameter RC controls the proportion of the rainfall which enters the routing store. A large value of RC causes more water to go into surface storage and causes a corresponding increase in the contribution of the surface store to the runoff from the catchment.
Parameters RDEL, RX and RK define the contribution of the routing store to the runoff. RDEL is the time delay, in days, between water leaving the routing store and leaving the catchment as runoff. RX and RK define the magnitude of the contribution of the routing store to runoff: Runoff = RK. (Current Volume in Store)RX
Parameter FC controls the amount of rainfall which is lost from the catchment by evaporation and transpiration. In the model, there is no simple relationship between FC and the amount of evapotranspiration. However, in general, an increase in the value of FC increases the estimated evapotranspiration.
Parameters GDEL, GSU and GSP define the contribution of the groundwater store to the runoff. GDEL is the time delay, in days, between water leaving the groundwater store and leaving the catchment as runoff. GSU and GSP define the magnitude of the contribution of the groundwater store to runoff: Runoff = (Current Volume in Store/GSU)GSP.
By adjusting the values of the parameters, an experienced hydrologist should be able to obtain a satisfactory catchment model, that is one which gives reasonable predictions of flows from the catchment. Alternatively, an automatic optimization may be performed.

DATA Requirements

Two sets of data are required to operate HYRROM:
In addition, measured or estimated daily values of open water evaporation (i.e., potential evaporation) are required. The data should be of good quality with no missing or unrealistically high or low values. For the optimization analysis, it is recommended that data for a period of at least one year are used. The maximum period allows is ten years. For the prediction analysis, any period of data can be used, although the maximum period which can be analyzed at one time is fifty years, and only dates between the years 1900 and 2000 are acceptable.
A data preparation program, HYLINK, is provided to assist in creating these files. To use HYLINK, the data must be supplied in ASCII (i.e., text) files. HYDATA files can be read directly in.


IBM-PC or compatible with 640K RAM. Most printers and HP 7475A plotter are supported.

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Incredible NetworksΤελευταία Ενημέρωση 27 Ιουλίου 2004 - Last Revised on JJuly 27th 2004
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