Possibilities of Applying Hydrological Methods for Determining Environmental Flows in Select Catchments of the Upper Dunajec Basin

Abstract

Our paper describes a method for determining environmental flows based on the use of the Tennant and Tessman methods – based on flow duration curves – as well as instream flows using the methods of Kostrzewa, the National Foundation for Environmental Protection and Water Management, and the Malopolska method. Calculations were conducted for the catchments of three rivers: the Ochotnica, the Wielki Rogoznik, and the Mlyniska – all located in the basin of the Upper Dunajec. Input data obtained from the Institute of Meteorology and Water Management, the National Research Institute, were observation series of daily flows for the years 2000-09. The hydrometric data were evaluated in terms of homogeneity and independence using the Mann-Kendall-Sneyers test. The following characteristic flows were determined: minimum flow, mean annual low flow, and mean annual flow. The authors were inspired to perform this analysis by Polish regulations requiring that the instream flow refers to needs of aquatic ecosystem organisms, but they do not take into account the needs of waterdependent ecosystems (wetlands). Therefore, we assessed the possibilities of applying hydrological methods to determine the environmental flow, taking into account the needs of both aquatic ecosystems and floodplains. The calculations revealed differences between the values of the instream and environmental flows and also allowed us to conclude that in all the analyzed catchments the computed instream and environmental flows were below the level determined by the average monthly flow. Based on the indicated ecological criterion, the Tessman method was recommended to determine environmental flow in the Upper Dunajec basin, but emphasizing that adaptation of methods should be carried out to calculate environmental flow, which will take into account physiographic, climatic, and natural conditions of studied basins.