A Long-Term Plan for the Nile Basin

Abstract

In an article on “The Nile Basin”, vol. 7, in Nature of August 16, p. 215, Dr. C. E. P. Brooks directs attention to the fact that the theory underlying what we have called lsquo;century storage’ is not given in the book. This was omitted because it was thought better not to make a book dealing with Nile projects more difficult by including in it complicated theoretical investigations. It is the intention to publish a full account of these separately; but it may be opportune to give here a very short summary of what has been done, and also to clear up a point raised by Dr. Brooks as to the correctness of the formula: R = 1.65 ΣâšN, on which our scheme of projects depends. This relates to a set of N observations the frequency distribution of which is approximately Gaussian when no account is taken of their order, Σ being the standard deviation and R the maximum accumulated excess or deficit of departures from the mean. In the case of a river discharge, R is the amount of storage required to meet accumulated deficits over a period N. The equation gives the mean value of R obtained from 71 sets of observations of river discharges, river levels, rainfall, temperature and pressure covering periods of from thirty to two hundred years, with two or three cases outside this range, and a mean period of 97 years.