Calculation and Forecast of Glacial Feed within River Basins

A two-stage method for calculating and forecasting glacier feed in river basins is presented. At the first stage, a number of morphological characteristics of a glacier complex are reconstructed based on regional glaciation monitoring data. At the second stage, a time series of average summer air temperature T_s at the average height of glaciers Z_mean is calculated, which is used to calculate the specific annual ablation layer Ab over the glaciation area. A method for regional prediction of annual ablation Ab with a monthly lead time at the height of the firn boundary Z_fg = Z_mean as a function of the predicted air temperature T_s has been developed and tested for the first time. To determine T_s at the beginning of May, regional dependencies of T_s on the air temperature in April T₄ have been established. The results of a regional study of the variability of the glacier feed index δ based on runoff measurements in river basins of Eurasia, North America, Central Europe, and Central Asia are presented. Index δ is equal to the ratio of the runoff volumes or average water discharges for the periods July–September and March–June. A method for forecasting the annual and vegetation runoff of the Rhone River (Switzerland, Alps) for 2025–2054 as a function of index δ has been developed.