Abstract
Surface water quality has a vital role when defining the sustainability of the ecological environment, public health, and the social and economic development of whole countries. Unfortunately, the rapid growth of the worldwide population together with the current climate change have mostly determined fluvial pollution. Therefore, the employment of effective methodologies, able to rapidly and easily obtain reliable information on the quality of rivers, is becoming fundamental for an efficient use of the resource and for the implementation of mitigation measures and actions. The Water Quality Index (WQI) is among the most widely used methods to provide a clear and complete picture of the contamination status of a river stressed by point and diffuse sources of natural and anthropic origin, leading the policy makers and end-users towards a more and more correct and sustainable management of the water resource. The parameter choice is one of the most important and complex phases and recent statistical techniques do not seem to show great objectivity and accuracy in the identification of the real water quality status. The present paper offers a new approach, based on entropy theory and known as the Maximum Information Minimum Redundancy (MIMR) criterion, to define the optimal subset of chemical, physical, and biological parameters, describing the variation of the river quality level in space and time and thus identifying its pollution sources. An algorithm was implemented for the MIMR criterion and applied to a sample basin of Northeast Italy in order to verify its reliability and accuracy. A comparison with the Principal Component Analysis (PCA) showed how the MIMR is more suitable and objective to obtain the optimal quality parameters set, especially when the amount of investigated variables is small, and can thus be a useful tool for fast and low-cost water quality assessment in rivers.
Highlights
Rivers have a pivotal role in ecological and human health as well as in the economic development of territories, representing the main water supply for domestic use, irrigation, and industrial activities
The Water Quality Index (WQI) proved to be a useful tool to obtain a clear and complete picture of the contamination level of a river stressed by point and diffuse sources of natural and anthropic origin, leading the policy makers and end-users towards a more and more correct and sustainable management of the water resource
Such index is often based on a significant number of environmental parameters describing the overall water quality and, recently, most of the studies have focused on reducing them in order to remove the redundant variables and lower the analytical and monitoring costs
Summary
Rivers have a pivotal role in ecological and human health as well as in the economic development of territories, representing the main water supply for domestic use, irrigation, and industrial activities. Their water quality has ever more worsened due to both natural processes and anthropic interventions, such as the discharge of industrial and municipal pollutants together with runoff from agricultural lands [1]. On the one hand, less inflow in rivers during draughts reduces the dilution of the contaminants introduced from human and natural sources; on the other hand, the more frequent occurrence of higher runoff due to intensive storms increases their load of pollutants. The rapid growth of population and economic activities, together with the urban sprawl, are pushing towards a higher demand of high-quality water not often matched by the locally available resources, while the discharge of insufficiently treated wastewater raises expenses for downstream users and has damaging effects on the aquatic environments [2]
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