Short term variations of a glacier-fed river

Abstract

The main factors determining the short term variations of the river Thjorsa in Iceland are rainfall and the melting of snow and glaciers. Time dependent spectral analysis was applied to investigate seasonal variations in the second order properties of the variations of Thjorsa and their relationships with temperature and precipitation.

In late summer a linear model of Thjorsa and the temperature and precipitation at the meteorological station at Haell provides a good fit of the observations. Because of non-linear effects connected with snow melting linear models are less appropriate during the winter although they can still explain a significant proportion of the variations of Thjorsa.

The most important information for predictions a few days ahead are past values of the river itself. Some improvement can be achieved by also taking meteorological observations into account.