River Basin Hydrological Balance Evaluation in Term of the Land Use Change Impact

Assessment of the land use impact on the processes of water balance in the river basin should be an indispensable part of integrated river basins management. This paper compares climatic conditions occurring during the long-term period (1951-1980), following the situation immediately after dry conditions (1993-1999) and extremely rainy dates (2009-2012) with emphasis to estimate the runoff components in the Žitava river basin: the Obyce sub-catchment, situated in its upper part (74.5 km²) in the Slovak Republic. Modelling of the land use change effect on the total hydrology balance of the river basin characteristics was performed using the hydrological model WaSiM-ETH. The model was applied to evaluate the vegetation type influence and the water balance change in the presently mostly forested river basin (1), altering its replacement by the permanent grasses (2) and bushes (3), with emphasis to different total water balance characteristics change. The present state land use data were taken from the Corine Land Cover of the Slovak Republic. Model results show that actual evapotranspiration would decrease from -1.3% in case of bushes in 2009 up to -32.5% in case of grass in 2011. However, 13.3% rise was considered for bushes in 2010. Total annual discharge shows its increment in all observed changes from 5.9% for bushes in 2010 up to 65.3% for grass in 2012. Only in case of bushes in 2011 there was observed slight decrease of about -3.1%. Regarding the very expected land use change, especially in connection with the ongoing global climate change, the estimation of the hydrology balance components is of utmost significance.