Evaluating water balance components for forested headwater catchment undergoing environmental changes

Evaluating seasonal and long-term variations in water balance at catchment scale can be useful for assessing the current status and trends in water resources availability. Components of water balance reflect meteorological and climate variability, and vegetation cover development.

The experimental catchment Uhlířská is a small forested headwater catchment in the Jizera Mountains, Czech Republic. The catchment was extensively deforested in the 80´s. Damaged trees long exposed to the effects of air pollutants were poorly resistant to wind and pests. In the 90´s, new spruce forest was planted. The catchment has been subject to long-term monitoring. The 19-year series of data including air temperature, rain and snow precipitation, discharge, groundwater levels, wind velocity, and air humidity, is examined.

Our study provides basic analysis of directly measured components of water balance (precipitation and discharge, annual and seasonal runoff coefficients). The study further deals with the evaluation of the unmeasured components of the water balance (evapotranspiration and water storage). An interception model was employed to calculate the interception loss. Potential evaporation and transpiration during vegetation seasons were estimated by Penman and Penman-Monteith methods. Snow sublimation was estimated in the winter seasons. Effect of the forest development during the period of interest was considered.

The catchment water balance equation suggests significant changes of the water storage over the observation period, implying its decrease in recent years. However, baseflow and deep water storage seem to be unchanged. This discrepancy could be partly attributed to the decrease in shallow water storage and/or more pronounced transpiration reduction in recent vegetation seasons.

The research is supported by the Czech Science Foundation Project No. 20-00788S.