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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 water-dependent 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. [ABSTRACT FROM AUTHOR]

Our paper evaluates the effectiveness of pollutant removal from stormwater in a semi-natural treatment plant and develops stochastic models of their transformations in a soil bed. The examined wastewater treatment facilities consisted of reduction chambers and a retention-infiltration reservoir. The following indicators of pollution were subjected to analysis: BOD5, COD, total suspended solids, and chlorides. It was shown that COD, total suspended solids, and chlorides are the indicators that have the greatest impact on stormwater quality. However, the possibility of removal of the analyzed pollutants from stormwater is affected by the sedimentation process occurring in the reduction chambers and in the retention-infiltration reservoir, as well as by the process of infiltration through the soil bed. The developed models of pollutant transformation during wastewater infiltration through the bed were presented as the regression equations, where the selected pollution indicators in the filtrate were the dependent variable, while the analyzed pollution indicators in water from the retention-infiltration reservoir, coefficients of constant reaction kinetics determined for each variable, and the time of infiltration of wastewater through the soil bed were adopted as independent variables. [ABSTRACT FROM AUTHOR]

Our article investigates the response of the synthetic unit hydrographs (SUH) to parameter changes using sensitivity analysis. The beta and Weibull probability density functions and the objective function that includes both the peak discharge and time to peak were chosen to construct the SUHs for a small mountain catchment. The absolute and relative dependences between the distribution parameter changes and changes in the peak discharge and time to peak are measured using the sensitivity analysis methods which include both differential calculus and numerical computations. The Weibull SUH turned out to be more sensitive than the beta SUH when modeling the maximum discharge. The impacts of both parameters of the beta SUH and one parameter of the Weibull SUH on the time to peak are comparable, while the influence of the second parameter of the Weibull SUH is weaker. The results of validation showed good efficiency of the models and compatibility with Snyder's model. They serve as an effective tool in assessing flood risk. [ABSTRACT FROM AUTHOR]