Experimental analysis for the entropy parameter evaluation

In the last years the target of optimal management of the surface water resources has characterized the needed to effectively estimate the rate of water discharge to maintain in perennial way a stream to the aim to guarantee the continuity of biological and physical dynamics of the fluvial system. Water, like sanctioned from the Rio conference and the Aia forum, is the unavoidable good through which allowing the survival of the planet and, like such, it must be protected and defended. At the same time, because the total and local climatic variations, water assumes the role of element of risk for the human health and for the ecosystems in a generalized way both in terms of quantity in the catastrophic events and quality like privileged path of polluting and of triggering in the alimentary chain. The extreme conditions represent anomalous situations to avoid whenever generated by anthropic activities, generally consequence of recovery requirements of water resource or management of the resources available. One of the aspects of particular relief, deriving from the pressing requirement to generate surface water storages for drinkable or pluribus purposes, is the evaluation of the minimum life instream that, even if for some aspects is an administrative technical parameter, represents the tool through which contributing for the balance of the water budget and guaranteeing the continuity of the river environmental systems. Present study applies, in a feedback process, the concept of informational entropy for river velocity profiles, giving the evaluation of the entropy parameter imposing the boundary conditions of the local velocity gradient dictated by the satisfaction of dynamic and biological equilibriums. Generally the common used methodologies require the estimation of a relevant number of coefficients and parameters related to meticulous and sometimes difficult field measures 2nd International Conference New Trends in Water and Environmental Engineering for Safety and Life: Eco-compatible Solutions for Aquatic Environments Capri (Italy), June 24-28, 2002 internet: www.capri2002.com M. Greco, D. Mirauda Experimental Analysis for the Entropy Parameter Evaluation Page 2 addressing the researchers in the use of abacuses or logical similitude in order to closing mathematically the flow problems. In alternative it is possible to employ new methodologies based on the concept of informational entropy and maximization of the same one, derived through the statistical observation of the variable in examination. The entropy velocity profile is a result of such theory that leads back its applicability to the evaluation of the single parameter depending on macroscopic variables of easy esteem and acquisition. In detail the value of the entropy coefficient can be obtained through several analytical relationship and mainly by the knowledge of the ratio between the average and the maximum cross section velocity or the local shear stress. Focusing the attention on the last condition it has been possible to formulate a general methodology, based on the sustainability of the local river ecosystem, through which impose boundary conditions for the local velocity gradient with respect to the selected biocenosis community and thus derive the value of the entropy parameter