Modèles d'étiage

Ingénieur du génie Rural, des eaux et des forets C.E.R.A.F.E.R., Antony

Résumé

The term "low-water flow" conveys a variety of meanings and ideas, which can, however, be summed up under two main headings ; 1) the extreme case or extreme conditions and 2) insufficient flow available to meet the demand. In addition, models are more especially suitable for 1) discharge prediction for the design of river structures and 2) discharge prediction (in the strict sense of the word) for flow management purposes. Among the models recently designed in France for the extreme case, the following merit closer attention;- (i) A model for the determination of the characteristic low water discharge, which offers the possibility of extending measured flow series by observed rainfall series (M. Roche). (ii) A regional model enabling the annual minimum of a mobile mean of given length to be estimated in terms of rainfall and catchment area characteristics (J. Dauty). (iii) A model for use in attempting to predict the minimum annual discharge (J. Bernier). Models designed to compare available supplies with requirements are based on the two following possible principles;- (i) Determination of discharge with respect to a given requirement level in order to be able to predict short-supply conditions (J. Astier). (ii) The construction of discharge models, which are then compared with the requirements, with the same object in view (J. R. Tiercelin). A discharge model has been developed for this purpose and a rainfall/ runoff model is now being prepared, to enable measured flow series to be extended by observed rainfall series, and in order to be able to allow for irrigation requirements.