Spatial features of tidal variability of the hydrological and hydrochemical characteristics in the Northern Dvina River mouth area during the winter low-water period

The paper considers tidal effects on the formation of the hydrological and hydrochemical characteristics of the mouth of the Northern Dvina River in the presence of ice cover were considered. The results of natural surveys at the river delta and near-mouth area in March 2014 were analyzed. No surveys as such were performed in winter formerly. It was found that short-term variations of flow rates during the winter low-water time might be traced at 85–95 km from the seaward border of the delta. The tidal effects upon the short-term variability of hydrochemical parameters appeared at 70 km from the delta seaward border. The tidal variations of all the considered parameters were most intense in the mixing zone of riverine and marine waters at the delta.