A rainfall-runoff model based on the Least Action Principle

One of the main problems faced by hydrologists is to characterize the impacts of climate change and variability on water resources availability and agricultural productivity. This is particularly crucial in West Africa, where the sensitivity of water resources to climate fluctuations was dramatically illustrated by the drought that struck the region for several decades. In most of existing conceptual and empirical rainfall-runoff models the use of ad hoe parameters and the lack of appropriate field data are the main causes of uncertainties in hydrological information. The physics-based models, derived from conservation laws considerations are in turn, more demanding in data quality and quantity whereas such data are not, as yet, available within the region. It is therefore of paramount importance to develop new tools that can permit optimal representation of hydrological interactions for water resources planning and management activities. The newly introduced Rodriguez-Iturbe's "Principle of Minimum Energy Expenditure" is generalized using the Least Action Principle. The implementation of this theory using Oueme River data (in Benin) shows that the model can offer some degree of remedy to the problem of inadequate hydrologic information, in the particular context of ungauged basin.