543agreed upon by the interested countries, is the working of the Equatorial Nile project, of which the h t component, the Lake Victoria Reservoir, has been constructed, fo which later must be added the Lake Kioga Regulator, the Lake Albert Reservoir, and the Jonglei Diversion Canal project. These involve protection against both drought and flood, and are more complicated than the cases considered in the present Paper. ACKNOWLEDGEMENTS Throughout the work described in this Paper, which haa extended over several years, the Author has had valuable advice and assistance from his colleagues in the Egyptian Ministry of Public Works: Mr R. P. Black, M.C., M.A., B.Sc., now scientific Consultant, Ministry of Public Works; and Mr Yusef Simaika, B.Sc., InspectorGeneral, Nile Control, later Under-Secretary of State, and now Technical Consultant.W Naguib Boulos, the Author's personal assistant for more than 30 years, haa done a great deal of work on the details of the Paper, assisted by the staff of Nile Control. To all of these the Author offers his thanks.The Paper, which was received on 17 June, 1955, is accompanied by twenty sheets of diagrams, from which the Figures in the text have been prepared. DiscussionM r W. N. Allan (Irrigation Consultant to the Sudan Government) said it was a notable achievement to have developed statistical equations in forms which fitted such varied types of phenomena, so that the consideration of a single case could be based on knowledge of the characteristics of a much larger sample. The Author had pointed out, in the conclusion, that each individual case must be treated separately, using as data the practical conditions by which it was governed. It was on that aspect of the subject, the practical consideration of individual cases, that Mr M a n commented, with particular reference to the effects and implications of the losses which in varying degrees were necessarily incurred in long-term storage.In the Author's statistical investigations such losses had been ignored, for reasons which were obvious. There was no absolute relation between a phenomenon itself and the losses, which would vary with the conditions of storage and the methods of regulation adopted. But in the practical consideration of any individual case, the losses could not be disregarded, since they affected the amount of storage capacity which was hydrologically desirable, the net usable draft which could be maintained, and the methods of regulation which were most likely to be suitable.To illustrate those points Mr Allan used the example of Aswan, not only because that was one of the cases which the Author had found to be difficult in regulation, but also because the rate of evaporation was high, and the losses were thus significant in relation to the total annual flows, so that their effects showed up clearly. For that site as a reservoir data were already available up to a capacity of about 130 milliards of cubic metres; from those Mr M a n had prepared a Table of annual losses extended to cover a much larger range, on th...

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London) said that the natural phenomena with which the Paper was concerned were on a grand scale, but it might be said that as much, if not more, was now known about the Shire and its catchment as about many British rivers. About a year ago he had been surprised to find that it was impossible to obtain any recorded flood information about a large river in the Severn area, and to be told by the people concerned^ that they had never bothered to collect such information.87. The Author had indicated that he did not accept that natural events had an entirely random behaviour. He had attempted, and Mr Morgan felt succeeded, to show that there was a remarkably close relation between the behaviour of sunspot activity, or its incidence, and climatic conditions. It was curious that there should be such an apparently close agreement. 88.If it was possible to predict solar behaviour, then clearly this would enable a short-term forecast to be made of the probable behaviour of rivers. In any event, even if one could forecast only the broad fluctuation of solar activity, to say whether it was increasing or diminishing at any time, a short-term forecast could still be made of probable river activity. 89. He had been in Rhodesia last February when there had been some excitement about the level to which Lake Nyasa would move. In the event, the agreement between the actual and predicted maximum levels had turned out to be much closer than anything he had hoped for at the time.90. The Author's formula for evaporation was a little curious dimensionally! Nevertheless, it was based on extensive data, it seemed to fit the facts, and no e c i a l coefficients were introduced. No doubt more information would be forthcoming in the future to give a further check, although the agreement in Table 4 was remarkably good. Possibly members had been able to apply the formula to information of their own, and it would be interesting to know the results.Sir Thomas Foy (Adviser to British Thompson Houston Co. (Canada) Ltd.) observed that the Author had stressed the delicate nature of the balance of the water account on Lake Nyasa, which was primarily attributable to the high evaporation from the lake relative to the rainfall and inflow. As the Author had stated, the average annual rainfall on the catchment down to Liwonde was about 49 in. The annual evaporation from the lake area was 60-70 in. It would readily be appreciated therefore that the annual water account of the lake area by itself was always in deficit. The free water was the amount contributed by the wet season run-off of the land catchment diminished by this deficit. t DISCUSSION ON LAKE NYASA AND THE RIVER SHIRE 21 3 92. The catchment area, including the lake, was 49,000 sq. miles while the actual area of the lake was 11,500 sq. miles. The ratio of land catchment to lake area was therefore only approximately 3.3 to 1, which was a very small figure. With high and fixed losses from the lake area, it was only to be expected that the effect on the free water in any year would be a magnificati...

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