The results of survey and hydrometric measurements and calculations made in the aim of the study of the rating curve of the cross-section in the river Dłubnia situated 810 m above inlet to water reservoirs were introduced in the work. The intensity of the water flow was calculated on the basis of the hydrometric data using the Harlacher’s method and for the help of the Chézy’s formula. It was stated that the water flows calculated using Chézy’s formula were considerably higher than determined the Harlacher’s method. The water flow calculated using Chézy’s formula with water depths carrying out 1.00 and 1.06 m is suitably above five times and above 1,5 times higher than calculated on the basis of hydrometric measurements. This difference gets smaller together with enlarging the water depth. The cause so considerable differences of the got calculations results of the water flow intensity is the influence of the arrangement of the longitudinal profile of channel bottom, disturbed the influence of the bridge. It was stated that the realization of the measurements of the bottom slope of channel on longer section below the considered cross-section of the river could show the possible influence of water damming up of the water flows of low states resulting from the

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