Impact of rainfall-runoff regime on water quality of chosen streams in the Sázava River catchment

Abstract

The aim of the contribution is to evaluate how hydroclimatic variables change due to the influence of advancing climate change and whether their change is reflected in the change in the water quality of surface streams. To evaluate the impact of climate change, four streams in the Sázava River basin were selected – Šlapanka, Sázavka, Jankovský potok and Chotýšanka. This is a watershed of a typically rural character, where the dominant source of pollution is agriculture. Data series of hydroclimatic parameters and water quality parameters provided by the ČHMÚ and Povodí Vltava s.p. were available. The selected parameters were: air temperature, total precipitation, height of snow cover in the basin and water temperature, conductivity, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, phosphate phosphorus and total phosphorus in streams. Data were analysed using regression analysis, correlation coefficients, and the Mann-Kendall trend test. Data analysis showed that hydroclimatic parameters changed in the observed period. The air temperature increased, its increase was proven by the Mann-Kendall trend test (Sázavka and Šlapanka River basin). Furthermore, the number of tropical days increased, the height and duration of the snow cover decreased. No trend was found in the rainfall totals data. There was a slight increase in stream water temperature, but this increase was not confirmed by the Mann-Kendall trend test. Nitrate concentrations were high in all selected streams and their concentrations stagnated or slightly decreased. Phosphate phosphorus concentrations also decreased. Dependency analyses showed that in selected river basins nitrates come from areal sources of pollution, while phosphates rather come from diffuse point sources of pollution. The planned management of activities in the river basin is therefore necessary to adapt to the character of pollution sources.