It is a well known fact that amount and type of catchment vegetation will affect its water balance. Through process of precipitation interception, vegetation coverage plays an important role in regulating processes as evapotranspiration and runoff.
Many studies have shown significant increase of water surface runoff, discharge and water yield after forest cover was removed. A clear conclusion can be drawn from this: grassed catchments decrease catchment evapotranspiration, while the opposite stands for forested ones. To help determine the exact relations between vegetation cover changes and water yield Zhang's model was developed.
In this graduation thesis Zhang model was put to the test to assess evapotranspiration and runoff of 125 hydrometric catchment areas in Slovenia and results were compared against national meteorological agency data.
Following, two additional extensions of Zhang model were developed to decrease deviations of model from measured data: first one based on determination of new constants, and second one on relationship between annual amount of precipitation and deviations of the model.
In the final part of this work, adapted model is used to assess impact of vegetation cover changes on catchment water balance of hydrometric catchment area of choice.