Abstract
Various methods for determining environmental flows can be based on hydrological characteristics, a combination of morphological and hydrological characteristics, or solely on hydraulic characteristics. Such methods may also be based on multi-criteria decision-making, where a low flow regime and its variability are considered. The methods for determining environmental flows as hydrological limits (sometime called desktop methods) are solely based on hydrological statistics and are believed to implicitly incorporate links to the state of river ecosystems. In the paper, we compared the performance of several methods in the set of the 137 official water balance inventory profiles of the Slovak Hydrometeorological Institute, which are evenly distributed over the territory of Slovakia. The analysis also accounted for the dependence between hydrological characteristics and environmental flow values. We also compared the frequency of the occurrence of their critical values (ecohydrological) in the reference periods 1931-1960 and 1991-2019. We proposed an intermediate system of regionalized relationships based on simple Tennant methods, which does not disturb the existing system of water allocations and uses in the water balance inventory.