Spring flood frequency analysis in the Southern Buh River Basin, Ukraine

The river floods are among the most dangerous natural disasters in the world. Each year, the spring floods cause the significant material damage in the different countries, including Ukraine. Knowledge of trends in such floods, as well as their probabilistic forecast, is of great scientific and practical importance. In last decades, the decreasing phase of cyclical fluctuations of the maximum runoff of spring floods has been observed on the plain rivers of Ukraine, including the Southern Bug River. In addition, there is an increase in air temperature. So, the actual task is the determine the modern probable maximum discharges estimates of spring floods in the Southern Buh River Basin as well as their comparison with the estimates that were computed earlier. It gives an opportunity to reveal possible changes of the statistical characteristics and values of the probable maximum discharges, to analyze and to discuss the reasons for these changes. For the investigation, we used the time series of the maximum discharges of spring floods for 21 gauging stations in the Southern Buh River Basin since the beginning of the observations and till 2015. The method of the regression on the variable that is based on the data of analogues rivers was used to bringing up the duration of the time series and restoration of the gaps. In the study, the hydro-genetic methods for estimation of the homogeneity and stationarity of hydrological series, namely the mass curve, the residual mass curve and the combined graphs. The distributions of Kritskyi & Menkel and Pearson type III for the frequency analysis were used. It has been shown in this study that the maximum discharges of spring floods of time series are quasi-homogeneous and quasi-stationary. It is explained the presence in the observation series of only increasing and decreasing phases of cyclical fluctuations, their considerable duration, as well as the significant variability of the maximal flow. The series of maximal runoff of spring floods are very asymmetric, which significantly complicates the selection of analytical distribution curves. The updated current parameters of the maximal spring flood runoff have not changed significantly. It can be assumed that such characteristics have already become stable over time, as the series of maximal runoff of spring floods already have phases of increasing and decreasing of long-term cyclic fluctuations.

Calculating the characteristics of flash floods on small rivers in the Mountainous Crimea

The maximal surface runoff from territory of the Crimean Mountains is represented as a runoff of small rivers that flow through the western and eastern part of the northern slope and from the southern coast. The materials from 54 water gauging stations (WGS) were used to characterize the maximum runoff during rain and meltwater-rain floods on the rivers in the Crimean Mountains. A modified reduction structure of a calculation formula was used for valuation of the maximal runoff of different origin flash flood for rivers at the Mountainous Crimea. The main parameters of the proposed model are summarized as dependencies on the average height of the catchments and generalized in the form of a map. It is also possible to use the second variant of the suggested method taking into account the factor of underlying surface is introduced. Comparison of the calculated values of maximal runoff shows good convergence with both the initial information, and the largest values in the observation period.

Descripción del potencial de aprovechamiento hídrico y de riesgos hidrológicos en el municipio de Xichú, NE del estado de Guanajuato

Hydrological potential at Xichu county was described. It is considered the main water reserve of the state of Guanajuato, but paradoxically inhabitants don`t have water supply minimal infrastructure. At Xichu is possible to find the most contaminated site with arsenic in Mexico: La Aurora mine tailings. The aim of this study was to know hydric exploitation potential (annual rain volume and fluxes of seven springs) and to describe danger scenarios (cartography of mine tailings of La Aurora, hydrological conditions of two main channels and to simulate maximal runoff using real rains data). Springs at karstic and fractured rocks produce significative volumes that can supply potable water to population all year. Mine wastes represents at least 600 000 t of materials that can be eroded. Rains over this region favor threat conditions by slides or remotion mass processes. It lacks hydrologic instrumentation to predict risks and take opportune decisions.

Substantiation of the Possibility to Use Dikes for Flood Regulation.

Effect of the flood regulation with the river floodplains was discussed, and a mechanism of the flood wave transformation with the basin channel network in the natural regime and during the floodplain banking was characterized. The possibility of dikes’ capacity use for cutting off the flood peak in extreme situations was substantiated and the relevant Chinese experience was analyzed. Theoretical basis for the channel network capacity management with pre-planned flooding of the “protected” floodplain areas was presented. The appropriated methods were developed; they included plotting of the maximal runoff calculated hydrographs, concurrent simulation of the flood wave passage and dikes capacities filling, more precise definition of parameters of the water-passing facilities in the dike body. Proposals on the designing of floodplain volumes and dikes intended for the flood runoff regulation were formulated. The Ingoda River (Transbaikal Kray) was taken as a study case. It was characterized by the flood maximal flows passage in different reaches due to the regulating impact of the bed and floodplain. Comparison of the real flood passage with the simulation results with the use of floodplain regulating capacities for this river was presented. Tentative results were the evidence of the principal possibility of the dikes capacity use in extreme conditions.

On the Issue of Assessment of Many-year Variability of the High Water Runoff of the South-Eastern Altay Rivers under the Conditions of Contemporary Glaciations (the Chuya River Basin as a Study Case)

The article is devoted to investigation of the contemporary glaciations’ influence on many-year variability of the spring-summer high water periods runoff characteristics. The issues of glaciers’ influence of the mountain river runoff are poorly studied; nowadays there is no unified vision of the glaciers’ impact on the high water maximal runoff. Regional dependencies of the high water runoff layer and its variation factors on the glaciations fraction and catchment height; data on water content cycles and phases can be used in calculations of any poorly studied rivers’ runoff.

Time of concentration in torrential catchments in Serbia

Maximal discharge Qmax,p is the basic input data for the design of longitudinal and transversal objects in torrential beds. Calculation of maximal discharge Qmax, on unstudied catchments is performed by the following methods: combined procedure (the theory of synthetic unit hydrograph and SCS methodology for the separation of effective rainfall Pe from total rainfall Pb), rational theory and theory of maximal runoff intensity. Rational theory is a suitable method with representative time of concentration Tc. The time of concentration was determined on the basis of investigation on 93 control profiles, south from the Sava and the Danube. Time of concentration and dominant physical-geography characteristics of the catchments were the basis for deriving the equations with regional significance [Tc=f(A), Tc=f(L), Tc=f(L, Lc, Iu), Tc=f(L, Iu), Tc=f(L, Isr), Tc=f(L, Iu, Isr)]. The relation between time of concentration Tc and lag time tp was determined [Tc=f(tp)].