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...

With a scheme of this kind there are many problems associated with its size, but as a dam problem, it is of moderate scale in regard to the height of its various elements. Nevertheless, there were one or two technical aspects which are interesting and perhaps unique. First of all, there is the question of the clay foundation. A typical vertical section in this clay showed slickensides, normally at an angle of about 45" to the vertical in all directions, criss-cross, and about 5-6 in. in length. It does seem to me that such slickensides are there as a result of stress. 2.In 8 46 of Paper 7047 the Authors refer to the clay as being over-consolidated by desiccation. I do not quite understand what this means, but would suggest a possible explanation. According to the geologists, this clay plane once had a surface many metres-l00 or more-higher than the present level, and the clay was therefore under a considerable vertical pressure. Since then, the vertical pressure has been reduced in comparison with the horizontal pressure. Recent studies throughout the world have indicated that the surface of the earth is under very high horizontal compression. The clay on which the dam is founded may already be in a state of considerable horizontal pressure, enough to have caused fissuring of the clay on removal of the vertical load, and there remains in the clay a horizontal pressure which is the maximum that it will take now that it has in fact failed. 3.From reference to 5 54 of Paper 7047 it will be realized, I suggest, that there is still uncertainty as to whether one should design for the minimum ultimate strength of clay or something greater, and it would seem to me appropriate in a case like this also to take account of the fact that the clay on which the dam is founded is already in horizontal compression.4. The second point of great technical interest relates to the deep sluices. Here the velocity of the water is high, and we were very concerned in regard to the specification for the concrete, to resist the forces which would apply-possibly cavitation, and certainly with silt and sand a certain amount of erosion. The conclusion was reached, confirmed by abrasion tests, that the hardest aggregate we could get should be used. Granite was definitely harder than the marble. We tried to make the mortar as hard as the granite, but did not quite succeed.5. During one flood season the sluices operated as free temporary openings. Considerable bed-load of sand and gravel passed through, particularly at sluice No. 5 when the invert was eroded to a rough surface with the aggregate exposed. The next season was the first year of operation of the dam and the flood was passed through the sluices, controlled by operation of the gates. After the flood, an inspection by diver was carried out and it was found that there were small areas of erosion. The area was then cofferdammed and de-watered and we found places where the surface had either been slightly worn or small pockets had been formed.6. Fig. D1 shows the patches being cut out rea...

Partners) said that the works described by the Authors did not represent the largest link system in the subcontinent for conveyance of water between rivers when compared with some works constructed before the Indus Basin Settlement Scheme or now projected under the Scheme. They had, however, the distinction of being the first link system completed under Indus Basin Project procedures through competitive bidding by international tenderers, and using mechanized as opposed to traditional methods of construction. t94. When the T-S-M-B LinkSystem was commissioned in April 1965 this meant that Phase I of the Indus Waters Treaty (1960) which was only signed in October of that year was completed on schedule. The total tender value of the works completed in contract periods varying from 31 to 38 months amounted to E33-7 million, i.e. an aggregate average certification rate in excess of El million per month. This achievement on schedule was a monument to team-work between the friendly countries (as they were known) who made the fmance available, the World Bank (acting as administrator to the Indus Basin Development Fund), the Government of Pakistan and their agents, WAPDA, the Irrigation Department and numerous other departments, the WPR and commercial organizations, the various Consulting Engineers and, not least, the Contractors.95. It was, indeed, the time factor which made it necessary to depart for the first time from traditional methods of construction for this type of work. This in itself posed problems of both design and construction. With respect to the former, it was as yet too early to evaluate reliably the extent to which all design criteria had been satisfied. In addition to the usual and sometimes controversial parameters involved in canal design, the design and review Engineers were faced with limitations of bed slope and wide ranges of opinion as to future operating conditions, with special reference to silt regime of the links. Future silt regimes of the main rivers would be materially affected by the progressive commissioning of the other Indus Basin Projects.96. On the Jhelum River, Mangla Storage, which was due to be commissioned in 1967, would result in major floods only being discharged downstream (Fig. Dl) Such waters discharged through the main spillways would, of course, be in the 'hungry' condition and lead to local degradation.However, when the Rasul Barrage and the Rasul-Qadirabad Link were commissioned in 1968, up to 19 000 cusec. would be diverted out of the Jhelum upstream of Trimmu. During the flood of July 1959 the peak discharge of the river at Rasul was 827 000 cusec., and in three days the river carried a sediment load of about 120 million tons, or twice the average annual load.97. Finally, with the completion of the Chasma-Jhelum Link in 1970 there would be injected into the system, a relatively short distance upstream of Trimmu, 22 000 cusec. of Indus waters carrying a different type of silt load. Similarly, Chenab and Ravi waters would be affected by the operation of the Qadirabad-Ba...

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