Water Balance Modelling on Small Forested Catchments

Abstract

The role of catchment management is very important in rainfall-runoff processes, particularly on small torrential catchments with extremely fluctuating discharges and sediment transport. Before taking measures in torrent channels one should first look at a catchment with special emphasis on land use, proper forestry and agricultural management and on area soil erosion control to reduce surface runoff by infiltration. To achieve better quantification of the significant components of the water balance, the WBCM (Water Balance Conceptual Model) was applied. This model can simulate a water balance quite well, when runoff data is available. In this study, a small catchment MALY POTOK, in the Czech Republic, was analyzed. Unfortunately, the outlet of Maly Potok is ungauged (small catchments are usually not measured). Three basic model parameters were therefore adjusted according to those determined on the Rokytenka catchment, which includes the Maly potok catchment area and which is gauged. The WBCM model was further implemented in a simulation of hypothetical scenarios representing changes in grassland, with the aim of quantifying the extent of the influence on surface runoff and on subsurface recharge. This simulation provides evidence that a 10% change in arable land area can significantly affect subsurface water recharge by infiltration of (plus or minus) 17% to 25%. This influence was computed in an “average” year. In a “dry” year it is still more significant. The trends in changes of surface runoff are even more considerable.