Vol 44, No 4 (2017)

The efficiency of the methods of spatial proximity and geostatistics, as well as physico-geographic similarity, is studied as applied to the evaluation of the key model parameters of ungauged watersheds to be used in river runoff calculation by SWAP model. The target geographic objects were 323 experimental watersheds of MOPEX project. The quality of model parameter estimates and reproduction of river runoff hydrographs was analyzed in the case of the use of different similarity methods, and the order of decisions to be made was developed for the problem of river runoff calculation from an ungauged watershed for the entire area under study.

Although the Volterra models are non-parsimonious ones, they are being used because they can mimic dynamics of complex systems. However, applying and identification of the Volterra models using data may result in overfitting problem and uncertainty. In this investigation we evaluate capability of different wavelet forms for decomposing and compressing the Volterra kernels in order to overcome this problem by reducing the number of the model coefficients to be estimated and generating smooth kernels. A simulation study on a rainfall−runoff process over the Cache River watershed showed that the method performance is successful due to multi-resolution capacity of the wavelet analysis and high capability of the Volterra model. The results also revealed that db2 and sym2 wavelets have the same high potential in improving the linear Volterra model performance. However, QS wavelet was more successful in yielding smooth kernels. Moreover, the probability of overfitting while identifying the nonlinear Volterra model may be less than the linear model.

Under the influence of all kinds of human activities, runoff decreased significantly in most river basins in China over the past decades. Assessing the effect of specific human activities on runoff is essential not only for understanding the mechanism of hydrological response in the catchment, but also for local water resources management. The Kuye River, the first-order tributary of the middle Yellow River, has experienced significant runoff declines. The coal resources are rich in the Kuye River Basin. In mined out area some cranny changed the hydrogeological conditions of the mining area and the hydrological process of the basin. In this study, the time series of runoff was divided into three periods at two critical years of 1979 and 1999 by precipitation–runoff double accumulation curve. The Yellow River Water Balance Model (YRWBM) is calibrated and verified to a baseline period in 1955–1978. Subsequently, natural runoff for human-induced period (1979 to 1998) and strongly human-induced period (1999 to 2010) is reconstructed using the YRWBM model. The YRWBM model performed well in simulating monthly discharges in the catchment, both Nash Sutcliffe coefficients in calibration and verification were above 70%, while relative errors in both periods were at less than 5%. The percentage of runoff reduction attributing to human activities was from 39.44% in 1979–1998 to 56.50% in 1999–2010. Further the influence of coal mining on river runoff was assessed quantitatively by YRWBM model simulation. The influence of coal mining on runoff reduction was 29.69 mm in 1999–2010 which was about 2.58 × 10⁸ m³/a. It accounted for 71.13% of the runoff reduction during this period. Coal mining became a dominant factor causing the runoff reduction.

The depth of soil freezing in river watersheds is a factor governing winter runoff formation. The freezing depth regulates the redistribution of stored soil moisture between thawed and frozen soil layers. The moisture stored in the thawed soil layer is spent for winter runoff, while that in the frozen zone forms snowmelt runoff. The depth of soil freezing has considerably decreased over the period of climate changes, resulting in an increase in winter runoff and greater losses of snowmelt runoff.

Identification, analysis and prediction of the erosion and sedimentation or the increase and decrease in river bed level are among the most complex and yet up-to-date topics of deposit hydraulics and river engineering. If cross structures in rivers and canals are also to be considered the complexity of flow pattern and deposit transfer increases. In this research using the one-dimensional mathematical model HEC-RAS 4.1 the effect of short dikes on flow hydraulic and the trend of sedimentation and erosion in the Karun River were simulated and analyzed within the boundaries of Ahwaz City. The area introduced into the model started from the Ghir dike to Khoramshahr. Moreover, the Mollathani, Farsiat and Ahwaz hydrometric stations were used as the upper limit, lower limit and calibration limit of the model, respectively. The flow was assumed to be quasi-unsteady and based on the existing knowledge of different methods and experiences with the methods in other studies the Toffaleti method was used to solve the deposit equations. The model was prepared and applied in the following four states: without dike and with dikes 0.7, 1.2 and 1.7 m above the average level in the desired areas. Finally, results of the model applied with and without short dikes revealed that the short dikes and dikes 1.2 m above the average floor level of modeled areas were significantly ineffective under hydraulic conditions and morphological changes. Moreover, the majority of changes in the river bed and all the morphological changes, in general, were the result of other factors. Dikes with heights of 1.7 m above the average floor level significantly caused sedimentation in the upstream and affected the hydraulics of flow.

The paper presents data on the concentrations of persistent organic pollutants in bottom sediments of subarctic lakes on Vaygach Isl. and in the Polar Cis-Urals in the Northern European Russia. Dioxin pollution is estimated at the background level, and the recorded levels of hexachlorobenzene fall within the concentration range identified in the bottom sediments of small lakes in the southwestern Arkhangelsk region. The specific character of the congener profile of polychlorinated dibenzo-p-dioxins and dibenzofurans in bottom sediments is demonstrated, suggesting a relationship between the pollution that forms under the effect of atmospheric transport of persistent organic pollutants from low latitudes in the past and present and the application of dioxin-containing organochlorine chemicals in timber industry.

Atomic-emission spectroscopy was used to determine the concentrations of Be, Ga, Nb, Ta, Y, Zr, Hf, Sc, Mo, U, and Th in subcolloidal, medium-pelite, coarse-pelite, fine-aleurite, and coarse-aleurite fractions of bottom sediments of Razdol’naya R. marginal filter. The concentrations of examined elements are maximal for the subcolloidal sediment fraction. The average concentration (n = 10) of elements in the soil and fluvial sediments (upstream of the mixing zone) were calculated and taken as background concentrations. The highest concentrations of Y, Be, U was shown to correspond to sediments in the zone of fresh and sea water mixing, which is accompanied by flocculation and sorption on Fe and Mn hydroxides and clay minerals (hydromica in fluvial sediments, and smectite in marine sediments).

Data of integrated gas-geochemical studies in the 45 cruise of the R/V Akademik M.A. Lavrent’ev in July 2008 were used to study the spatial distribution of methane in the surface seawater layer, the distribution and qualitative composition of hydrocarbon gases in bottom sediments of the northwestern continental shelf, northeastern slope of Sakhalin Island, and Deryugin depression in the Sea of Okhotsk. The specific features of the methane anomalies that form in this case are considered. Tectonic faults and the distribution of oil-and-gas-bearing structures are the main factors governing the formation of hydrocarbon gas fluxes in the study area. The surface water in the entire examined area was found to be oversaturated with methane. A developed model was used to calculated methane fluxes at the water–atmosphere interface and to identify areas with maximal fluxes (up to 324 mol/(km² day).

The regional specifics of water use in the transboundary basin of the Ural R. are studied. The diverse problems of dependable water use in the region are caused by the interaction of natural and anthropogenic factors. Considering the space and time variations of river runoff, a possible approach to solving water use problem is runoff regulation. To effectively solve the problem of water use requires the search for an organizational and legal form of institutional interaction within the transboundary basin of the Ural R.