Explore the vast range of titles available.

Statistically significant changes in the times of the appearance of stable ice formations and the duration of the freeze-up period were revealed at 12 hydrological gages on the rivers of the Votkinsk Reservoir catchment area for the period 1936–2018. Statistically significant shifts by 7–14 days toward later times were found in the appearance of ice formations along with a decrease in the duration of the freeze-up period by 6–18 days.

The method of temperature coefficients along with detail digital maps and GIS-technologies were used to develop a model of spring snow melting, which takes into account the high-accuracy spatial distribution of meteorological data, relief features, and soil-vegetation cover. The effect of slope aspect on the processes of spring snow melting was evaluated with the use of correction coefficients, and a procedure for determining their optimal values was developed. A method was proposed for verification and validation of the calculated spatial distribution of snow cover with the use of space monitoring data.

A methodological approach is developed to the analysis of long-term series of observations of hydrological characteristics including the testing of the hypothesis of randomness both for the full series and for their parts; the diagnosis of intraseries dependence of time series; the testing of the hypothesis of homogeneity of the parts of observations series under comparison; the identification of change points. Statistically significant changes in the dates of river ice formation in the Votkinsk Reservoir catchment were revealed for the periods of 1975–2012 and 1983–2012, whereas the entire observation period (1936–2012) did not reveal such changes. A possibility of localization of change points for the observation series was assessed using the inversion test.

A statistical analysis of the dates of ice formation and ice destruction in the rivers of the Votkinsk reservoir catchment was carried out, including testing the hypothesis of randomness for both the full series of observations and their parts; autocorrelation diagnostics of the time series; verification of the homogeneity hypothesis of the series of observations and the aggregate index. The results indicate that there are statistically significant changes in the ice formation and ice destruction dates occurring in recent years in the rivers of the Votkinsk reservoir catchment.

The assessment of the long-term variability of the rivers water content in the catchment area of the Votkinsk Reservoir for gauge stations (g/s) with the longest observation series (1939–2018) has been carried out. During the period under review, almost all g/s showed the presence of a statistically significant positive linear trend. The difference-integral curves revealed a violation of the stationarity of long-term observation series, and an analysis of the intra-annual distribution of monthly and seasonal runoff in% of the annual for two periods was carried out: 1956–1976 and 1977–2018. For the period 1977–2018 a decrease in the share of spring runoff (by an average of 7%), as well as an increase in the share of summer-autumn runoff and winter runoff by 18.4 and 24%, respectively, were found for almost all rivers in the study area.

The article is devoted to study of the conditions of the spring flood runoff formation in high water years. The authors analysed the dependences of the runoff layer on the main factors such as the maximum water storage in the snow before the beginning snowmelt, sum of the positive air temperatures, sum of the precipitation during the spring flood and autumn moistening. It was revealed that the determining factors in the formation of the spring flood runoff layer on the rivers of the Votkinsk catchment are the maximum water reserve in snow and precipitation that fell during this period.

The article is devoted to a comparative analysis of the results of snow cover interpreting on satellite images using various software tools on the example of individual basins in the catchment area of the Votkinsk Reservoir. Space images were decoded in ArcGIS and MultiSpec using the methods of interactive supervised classification with training and maximum similarity, and in the ScanEx Image Processor software- using NDSI and NDFSI indices. It was found that the use of the NDFSI index increases the accuracy of determining the areas occupied by snow for forested parts of the catchment by an average of 30%.

The paper presents a review of studies by Russian and foreign scientists on the formation of bottom sediments in valley reservoirs. The typing of the main factors according to the time of occurrence and the source of income was carried out. Methods for studying the processes of bottom sediments formation are identified. This is an assessment of the material collapsed volume at coastal stations, the calculation of the solid flow in the main tributaries, sampling of bottom soil, repeated depth measurements. The organization of comprehensive studies of the input and expenditure components of the sedimentation balance and modelling of spatial and temporal changes in the bottom relief using GIS-technologies is important for predicting the siltation of reservoirs.

Scientific–methodological principles are proposed for zoning valley reservoirs and studying the spatial heterogeneity of their bed shape based on criteria developed in the form of integral dimensionless morphometric coefficients. Up-to-date digital maps are used to improve the hydromorphological zoning of the Kama Reservoir.

The use of GIS technologies for modeling the spatial distribution of snow cover in spring is considered. The authors developed a method for the snowmelt calculation by the example of the Votkinsk Reservoir catchment area. It is proposed to take into account the uneven distribution of snow cover across the catchment depending on the terrain features. The paper estimates how the raster cell size variation affects the displaying the modeling results of the spatial distribution of snow cover.