DISTRIBUTION OF RIVER RUNOFF AND ITS CLIMATE FACTORS IN AVERAGE AND EXTREME YEARS

Abstract

Schematic maps of spatial distribution of seasonal precipitation amounts and average air temperatures were obtained for the areas studied in years with normal and extreme values of annual river runoff. Data on precipitation for January–December (I–XII) and on average air temperatures for June–September (VI–IX) during 1961–1990 collected at 93 meteorological stations located along 30.20°–44.08°N and 67.20°–82.98°E, altitude 122–4 169 m above sea level, were used in the maps’ compilation. For each point-element (i.e. a meteorological station with proper data), the ordinates of an integral empirical function of distribution of probabilities P were calculated from these data for a 30-year sample period and for each year were received average values and standard deviations of P. In characteristic years were revealed, significant differences of spatial distribution of climatic factors and runoff. It was found out also that the spatial distribution of the total volume of glaciers melting is less variable in the years with extreme water yields compared to the average years. This peculiarity is very beneficial for hydropower and agriculture sectors because it provides additional natural ability to stabilize water balance of reservoirs. Piecewise multi-factor linear equations were obtained to calculate the statistical probability of glaciers’ total melting in low and high flow years as a function of geographical coordinates and the average altitude of firn boundary.