This paper contains the results of research of the content Na, K, Ca and Mg in waters drained from three agricultural river basins in Lower Silesia. The investigations covered two objects situated close to Wrocław and one in the border region between the Bolków-Wałbrzych Plateau and the Wałbrzych Mountains. The effect of the agricultural use of the land on changes in the concentrations of the analyzed macroelements in the water flowing from the river basins has been assessed. Between 58 and 91 samples of waters for chemical analyses were taken once a month. Our analysis has shown that the concentrations of the analyzed elements were considerably different, both in the water flowing into and from the basins. The effluent water from the river basins was characterized by an elevated content of calcium and low concentrations of potassium. However, the content of magnesium was typical for the conditionsin Poland. The content of magnesium in waters drained from all the river basins was higher than in the water flowing into the basins and the correlation coefficients for the concentrations in both of these cross-sections ranged from 0.7846 to 0.8603. Likewise, for sodium, calcium and potassium, dependences were found between the concentrations of these elements above and below the analyzed objects but the correlation coefficients were lower. Distinctly lower values of the correlation coefficients were obtained for the village of Samotwór. The agricultural use of the river basin area contributed to a higher magnesium and calcium content in waters and an insignificantly raised content of sodium. These changes were accompanied by a decrease in the concentration of potassium. It has been found out that differences in the Na:K:Ca:Mg ratio between the seasons of the year (early spring, late summer) are connected with the dynamics of the calcium concentration. The growth in the concentration of this element caused evident differences in the Ca : Mg ratio, reaching 0.7 to 1.2. An increase in the value of the Ca : Mg ratio in late summer reduces the outflow of potassium in most cases. Agricultural practice does not show any direct influence on seasonal changes of the Ca : Mg ratio and its effecton the value of this ratio is not unambiguous.