Simulation and reconstruction of parameters of streamflow and glacier mass balance in the Northern Caucasus

Abstract

The work was aimed at numerical modeling of spatial-temporal variability of the river Terek seasonal (April to September) streamflow characteristics and long-term fluctuations of components of annual glacier mass balances in this basin and on the adjacent territories. Mass balance of glaciers Djankuat and Garabashi was calculated. Simulation was performed by means of stochastic modeling and discrete data presenting fields of main meteorological parameters (precipitation, air temperature and humidity) having effect on the streamflow. Realization of this approach is complicated by the fact that spatial representativeness of hydrological and meteorological sites are not corresponding one to another. Data on the runoff is clearly related to the total drainage area closed by a gauging station. And for this data we study a relationship with meteorological parameters which are measured at a non-regular observational network whose spatial representativeness is unknown. These stations are generally located beyond the area under investigation (Fig. 2). Similar problem exists when we analyze a relationship between components of the mass balance of individual glaciers (Djankuat and Garabashi) and the above climate characteristics measured at some stations located on the whole Caucasus territory. The same takes place when long-term indices of width and density of tree annual rings obtained in upper reaches of the river Kuban’ are used for analysis of variations of the runoff and the glacier mass balance in the river Terek basin located at a distance of 100-150 km from the Kuban’ dendrologic sites.

To solve the problem we used a wide number of factors which directly (various information about the climate) or indirectly (indices of the climate dryness, wood ring characteristics) characterize conditions of formation of annual and seasonal river runoff and components of glacier mass balance in the North Caucasus. Use of all obtained information made possible the following results: a) new formulas for the calculation of seasonal runoff of the Terek river at the seven gauging stations for 1901–2010 years were derived and verified with independent data; b) significance of various arguments in these formulas was assessed to describe variability of function; c) for the first time relationships between the equilibrium line altitude (ELA), the index of area of accumulation (AAR), and components of the mass balance of the glaciers Djankuat and Garabashi were obtained; d) a technique for regional calculation of average accumulation on these glaciers was developed by using data on ablation and ELA.