Applying the stocking index to the determination of the curve number parameter in the forest catchment area

The Soil Conservation Service-Curve Number (SCS-CN) method was chosen to calculate the effective precipitation used in hydrological modeling. The assumption of the method is to correlate effective precipitation with the type of land cover, the type of soil and moisture conditions. All these factors include a dimensionless CN parameter. In the analysis, a modification of forest cover was used, taking into account the forest stand feature called the stocking index. Analyses were carried out for the forest catchment of the Łutownia river located in north-eastern Poland. Model calculations for the analyzed hydrographs using the value of the CN parameter with the stocking index and the original method showed that the optimal value of the CN parameter indicated in the results of model calculations ranged from 42.8 to 43.8. These values were similar to the parameter CN = 43.9 calculated according to the method incorporating the stocking index.

Recommendations for Resource Managers

• 1.

  Dividing the entire basin into subbasins will provide details that may be characteristic of a given subbasin.

• 2.

  Applying the smallest possible divisions will allow the soil group to be determined accurately.

• 3.

  To estimate the coefficient of the CN as precisely as possible, additional stocking index values should be used.