Delay of Run-off from a Glacier Basin

The main problem discussed in the paper is the delaying effect on run-off exerted by a glacier during the first part of the summer. A method of investigating this problem is suggested and applied to the conditions in 1957 at Mikkaglaciären in northern Sweden.As a consequence of the delay, the summer can be subdivided into three main periods. Period I exhibits a run-off deficit in relation to what may be expected from the amounts of water supplied by melting and rain, while period II involves a corresponding excess run-off through the release of stored and delayed water. Period III is a pseudo-balanced period in the later part of the season, with a correspondence between the volumes supplied (generated) and discharged.The applied method is a relative one. Regression equations are formulated during period III between the daily water volumes generated and the meteorological reference parameters and applied to the earlier periods for estimation of the water generation. Regard is paid to “the relative area of melting” (p. 6) to account for the larger snow areas outside the glacier in the earlier periods. The generated volumes used for the regressions were determined by graphical and numerical recession analysis (pp. 16 ff.). Because recession did not occur undisturbed by melting, the recession factor was determined by successive approximations, using the preliminary results for determining corrections (by regression analysis) for the “first-day run-off” caused by melting. Estimation of the recession factor by Markov analysis of the measured discharges was also tested.The results and the discussion of the causes (pp. 24 ff.) are summarized on p. 29. The main result is the finding that a volume of water of the order of 25% of the total summer discharge was delayed from the early to the middle part of the summer.