A TOOLBOX FOR SEDIMENT BUDGET RESEARCH IN SMALL CATCHMENTS

This study presents a dataset on long-term multidisciplinary glaciological, hydrological, and meteorological observations and isotope sampling in a sparsely monitored alpine zone of the North Caucasus in the Djankuat research basin. The Djankuat glacier, which is the largest in the basin, 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 dataset features a comprehensive set of observations from 2007 to 2017 and contains yearly measurements of snow depth and density; measurements of dynamics of snow and ice melting; measurements of water runoff, conductivity, turbidity, temperature, δ¹⁸O, δD at the main gauging station (844 samples in total) with an hourly or sub-daily time step depending on the parameter; data on δ¹⁸O and δ²H sampling of liquid precipitation, snow, ice, firn, and groundwater in different parts of the watershed taken regularly during melting season (485 samples in total); measurements of precipitation amount, air temperature, relative humidity, shortwave incoming and reflected radiation, longwave downward and upward radiation, atmospheric pressure, and wind speed and direction – measured at several automatic weather stations within the basin with 15 min to 1 h time steps; gradient meteorological measurements to estimate turbulent fluxes of heat and moisture, measuring three components of wind speed at a frequency of 10 Hz to estimate the impulse of turbulent fluxes of sensible and latent heat over the glacier surface by the eddy covariance method. Data were collected during the ablation period (June–September). The observations were halted in winter. The dataset is available from PANGAEA (https://doi.org/10.1594/PANGAEA.894807, Rets et al., 2018a) and will be further updated. The dataset can be useful for developing and verifying hydrological, glaciological, and meteorological models for alpine areas, to study the impact of climate change on hydrology of mountain regions using isotopic and hydrochemical approaches in hydrology. As the dataset includes the measurements of hydrometeorological and glaciological variables during the catastrophic proglacial lake outburst in the neighboring Bashkara valley in September 2017, it is a valuable contribution to study lake outbursts.

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 (K_sn) 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.