L' hydrologie nord-alpine et la sécheresse de 1976

Abstract

The 1976 Spring drought and heat had hydrological consequences in the Northern Alps which are interesting to be studied because of their variety. The deficiency of the pluviométrie totals from december 1975 to june 1976 (the lowest ever recorded) caused the lowest wafer levels ever observed in may average monthly discharge and june for pluvial supplied streams = 0,20). 1976 monthly discharge As the snow cover was thinner than usual because of less important snow falls, the deficiency of the discharge for the snow supplied streams was rather high (0,50 to 0,60 of the usual monthly discharge). The peak value of the monthly average flows occurred in may and not in june due to the early heavy heat. This one and this exceptional daily insolation from may 1st to june 24th (50 % days had more than 11 hours of sun) caused surplus discharges in may (1,20 to 1,68 of the normal value) for high altitude streams (having more than 20 % of glacier area in the river-bassin) .