ИСТИНА

Water quality monitoring networks typically involve field measurements with time resolution ranging from daily or several times a week to just several times a year. This time step directly affects the reliability of any related calculations. We addressed the issue of setting the optimal monitoring frequency for different practical and research purposes. It is shown that monthly or even seasonal observations can be sufficient to estimate the annual chemical yield of a river, but to better describe the seasonal dynamics of the chemical flow it is necessary to increase the sampling frequency to at least twice per month. To explore the relationship between the water discharge and chemistry and to improve the model calculations dependent on chemical input it is necessary to establish the most detailed observation framework covering all key points of a yearly hydrograph. Regardless of specific objectives, it is recommended to always set flexible monitoring dates in accordance with the rivers flow regime.