Long-term development of discharge and nitrate concentrations in the Little Carpathians headwaters

Abstract

One of the requirements imposed by the Water Framework Directive 2000/60/EC (WFD, 2000) is to analyze and predict long-term evolution of surface water quality parameters. During 28-years period (1991–2018), the concentrations of selected pollutants were monitored in the Little Carpathians headwater basins by the Institute of Hydrology, SAS. In this study we analyse the long-term development of runoff and nitrates nitrogen concentrations in the Parná River at Horné Orešany water gauge station during the period 1991–2018. Discharges in the Parná River decreased slightly, but the trend is not statistically significant. In the case of nitrate nitrogen concentrations the marked decrease occurred in this river basin from the value of 5.11 mg l during the years 1991–1995 to the value of 2.49 mg l in the years 2015–2018. The relation between discharge and nitrate concentration was used to derive exponential empirical relations for estimation of the nitrate nitrogen concentrations in the stream based on mean daily discharge during the sampling day. These equations can be used for indirect estimation of nitrate nitrogen concentrations when they were not measured directly.