The doctrine of prior appropriation which basically advocates historical rights isrnone of the doctrines which have influenced the question of the right to divert thernwaters of international water courses. This doctrine which may be implementedrnsuccessfully for determining rights with in one country, its application where thernclaim for the right to the use of a water course involves nation states is jound tornbe more problematical. The doctrine in its meaning of prior in time is prior in rightrnis no longer considered a controlling principle of international water law. Prior usernor existing use which this doctrine held as dispositive, is relegated to the statusrnof one of the relevant factors with the advent of the principle equitable utilization.rnDespite the general acceptance of the notion that prior uses are merely one of thernfactors to be considered in the determination of equitable utilization, nation statesrncould not reach at clear agreement on the issue of what weight should be 'given tornexisting uses compared to other relevant factors. This arises from the claim ofrndownstream states, which usually are prior users, to the preferential treatment ofrnexisting uses. This clashes with the accepted principle of equitable utilizationrnsince the later does not recognize hierarchy among the factors to be considered inrnthe determination of what amounts to equitable share. Such a situation is alsornreflected in the tension between the principle of equitable utilization and thernnotion of causing no significant harm to other water course states. Thisrncontroversy which results from the conflicting approaches over the issue of whichrnrule takes precedence stands as one of the most problematic aspect ofinternational water course law. The prevalence of no significant harm rule in itsrnapplication to water quantity issues presents difficulties on the settlement ofrncontroversies over allocation of disproportionately used international waterrncourses by giving, like the doctrine of prior appropriation, complete priority tornexisting uses. This competes with the principle of equitable utilization which mayrnallow the causing of significant harm so long as it results from a use which isrnequitable when viewed by taking into account all the relevant factors. The case inrnthe Nile depicts the tension created because of the unresolved conflict betweenrnthe claim to maintain the status quo and that of equitable allocation of the sharedrnwatercourse. The conflict between the claim of Egypt for the absolute protection ofrnprior uses and that of the upstream riparian states for the reallocation of thernresource, which is also revealed in the disagreement on the relationship of therntwo competing principles, has remained at the centre of the controversies overrnthe issue of sharing the Nile waters.