This study is focused on the comparison of streamflow composition simulated with three well-known rainfall–runoff (RR) models (ECOMAG, HBV, SWAT) against hydrograph decomposition evaluated with End-Member Mixing Analysis (EMMA). In situ observations at two small mountain testbed catchments located in the south of Pacific Russia are used. All applied RR models and EMMA analysis demonstrate that two neighboring catchments disagree significantly on the mutual dynamics of the runoff sources. The RR models' benchmark test is based on proximity to EMMA hydrograph composition. Different aggregation intervals (season, month, and pentad) were applied to find a reasonable generalization period ensuring the clarity of results. ECOMAG is most conformable to EMMA outcome; HBV reflects flood events well enough; SWAT exhibits distinctive behavior compared to the other models. It is shown that, along with standard efficiency criteria of simulated and observed runoff proximity, EMMA analysis might provide useful auxiliary information for the validation of modelling results.

Presented are the results of adapting and testing the method of the genetic disintegration of the runoff hydrograph based on the use of natural chemical tracers in the framework of the End-Member...

The development of an optimal scheme for evaluation of maximal water discharges is discussed, including adequate probability distribution laws, an effective procedure for their approximation based on observational data, and reliable goodness-of-fit tests for analytical and empirical distributions. One-dimensional probability distribution laws are systematized. Promising distributions were identified, including generalized distribution of extreme values, lognormal distribution, Pearson type V power distribution, and GPD, for evaluating maximal discharges. The available methods for approximating analytical curves, including the up-to-date method of L-moments are considered. Parameter estimation algorithm based on L-moment method for Pearson type III distribution is considered. Pearson type III distribution, lognormal distribution, GEV, and GPD are compared in the approximation of maximal water discharges in rivers of Austria, Siberia, Far East, and the Hawaiian Islands.

A set of problems related to formation of areas homogeneous in hydrological aspect is considered. A methodology of regionalization is proposed. New analytical methods of the methodology are intended of solving such problems as (i) the problem of regionalization and (ii) the problem of constructing of a classification for river drainage basins. Efficiency of the methods proposed has been tested on the problems, which arise in the process of constructing classifications for river drainage basins, and also on the problem of territorial regionalization of Japan islands. Investigations, which presume obtaining a set of morphometric and hydrographic characteristics of catchment areas, allow one to study conditions of extreme inundations. It has been discovered that boundaries of the areas have striking similarities in the spatial location of geological structures. Furthermore, these are coincide with the boundaries of the main tectonic fields.

Methods for the analysis of the formation of river water chemistry based on mixing models are discussed. An analytical solution for a mixing model of four recharge sources is given along with the...