The model builder is used to modify Curve Numbers (CN-values) assigned to individual grid cells of the raster-based rainfall/runoff model
In principle, the CN-values for this model are based on "hydrological soil classes". The values of landuse and climate zone (which is assumed to have an effect on soil depth) are introduced as correction factors. Thereby, the correction factor is not directly applied to the CN-value but to the S-value, which is a function of the CN-value:
The S-value (with the dimension "Millimetres" can be understood as the maximum capacity of water a certain soil can store. Correction factors larger than 1 will increase the S-value and thus decrease the CN-value.
The climate classes for Jordan were predefined by the Consultant, and their extent has been outlined under ArcView GIS. In principle, they represent the agro-climatic zones in a simplified way. In the semi-humid areas of the mountain zones, soil depth is greater and thus the capacity of the soil to store water is higher. This results in lower runoff volumes. The opposite is due for the arid areas of the eastern part of the country.
The present version of the model builder is limited to modifying the correction factors for individual classes. The code (number) and the description of the classes cannot be edited through this interface.
For the purpose of editing the values, the table is copied to a temporary table.
Pressing the "exit key" will exit the form without saving.
Pressing the "save key" will save the table values and exit.