Factors Controlling Contemporary Suspended Sediment Yield in the Caucasus Region

This paper discusses the joint impact of catchment complexity in topography, tectonics, climate, landuse patterns, and lithology on the suspended sediment yield (SSY, t km−2 year−1) in the Caucasus region using measurements from 244 gauging stations (GS). A Partial Least Square Regression (PLSR) was used to reveal the relationships between SSY and explanatory variables. Despite possible significant uncertainties on the SSY values, analysis of this database indicates clear spatial patterns of SSY in the Caucasus. Most catchments in the Lesser Caucasia and Ciscaucasia are characterized by relatively low SSY values (<100–150 t km−2 year−1), the Greater Caucasus region generally have higher SSY values (more than 150–300 t km−2 year−1). Partial correlation analyses demonstrated that such proxies of topography as height above nearest drainage (HAND) and normalized steepness index (Ksn) tend to be among the most important ones. However, a PLSR analysis suggested that these variables’ influence is likely associated with peak ground acceleration (PGA). We also found a strong relationship between land cover types (e.g., barren areas and cropland) and SSY in different elevation zones. Nonetheless, adding more gauging stations into analyses and more refined characterizations of the catchments may reveal additional trends

Causes and consequences of the streambed restructuring of the Koiavgan Creek (North Caucasus, Russia)

The restructuring of the lower reach of the Koiavgan Creek channel (the right bank tributary of the Djankuat River) occurred on 1 July 2015 after continuous rainfall with a total precipitation amount of 227 mm. This led to the breakthrough of the Djankuat Glacier lateral moraine. The lower reach of the creek channel was initially formed at the junction of the bedrock slopes and lateral moraine and descended sharply at the end of the moraine to a wide glacial valley of the Djankuat River. The part of the channel from the end of the moraine line to the creek’s outlet in the bottom of the glacial valley had a height difference of 125 m at a distance of about 250 m. The active landslide has been recorded in the place of future breakthrough based on interpretation of 2014 summer satellite image. The linear erosion began to form on the wall of the disruption. Thermokarst processes probably also contributed to this breakthrough. The total volume of sediment eroded during the breakthrough and for four years after is 156 500 m3. The breakthrough has formed the largest sediment cone 300 meters wide and more than 200 m long in the bottom of the Djankuat River valley

Hydrological, meteorological observations and isotopes sampling results during 2019-2020 at Djankuat Glacier Station in the North Caucasus, Russia

This is an update of a dataset on the long-term complex glaciological, hydrological, meteorological observations and isotopes sampling in an extremely underreported alpine zone of the North Caucasus. The Djankuat research basin is of 9.1 km2, situated on elevations between 2500 – 4000 m, by 30% covered with glaciers. The biggest in the basin Djankuat glacier was chosen as representative of the central North Caucasus during the International Hydrological Decade and is one of 30 'reference' glaciers in the world that have annual mass-balance series longer than 50 years (Zemp et al, 2009). The original dataset covers 2007-2017, this update - 2019-2020. In total, the dataset contains the result of yearly measurements of snow thickness and density; dynamics of snow and ice melting; measurements of water runoff, conductivity, turbidity, temperature, δ18O, δ2H on the main gauging station with a one-hour or several-hours step depending on the parameter; data on δ18O and δ2H sampling of liquid precipitation, snow, ice, firn, groundwater in different parts of the watershed regularly in time during the melting season; precipitation amount, air temperature, relative humidity, shortwave incoming and reflected radiation, longwave downward and upward radiation, atmospheric pressure, wind speed and direction – measured on several automatic weather stations within the basin with 15 min – one-hour step; gradient meteorological measurements to estimate turbulent fluxes of heat and moisture, measuring three components of wind speed at a frequency of 10 hertz to estimate the turbulent impulse heat fluxes over the glacier surface by the eddy covariance method. The observations were held during ablation period June-October and were interrupted in winter. The dataset will be further updated. The dataset can be useful for developing and verifying hydrological, glaciological and meteorological models for high elevation territories, to study impact of climate change on hydrology of mountain regions, using isotopic and hydrochemical approaches to study mountain territories