Recreational Water Quality Index
Recreational use of water can deliver important benefits tohealth and well-being. Yet, there may also be adverse healtheffects associated with the recreational use if the water ispolluted or unsafe (WHO 2005). Hence, the surface waterquality must be monitored because its quality could bechanged from either natural or anthropogenic sources.
The exposure to toxic chemical substances in recreationalwaters is a key issue, and it varies depending on the differentrecreational activities. Therefore, the form of recreationalactivity will play a significant role. Routes of exposure willbe direct surface contact, including skin, eyes and mucousmembranes, inhalation and ingestion. So, frequency, extentand likelihood of exposure are crucial parts of the evaluation.
Indices are numerical values that seek to encompass magnitudesof several parameters, whose purpose is to derive anon-dimensional number, as a combination or as a function ofanalytical data from a water sample. These indices allowcomparison, if they were obtained by the same mathematical–analytical method, between different water samples takenin different places and times. Furthermore, it is possible to getquick and brief results to study and to monitor the evolution offresh water over time and throughout its course (House 1990;Alberti and Parke 1991; Valcárcel 2011).
Water quality index may have disadvantages such as loss ofinformation about individual variables and their interaction, lackof fit to different types of water uses and sensitivity loss of theresults according to the way index was developed (ambiguity,eclipsing and rigidity) (Swamee and Tyagi 2007). It is possiblethat themeasure, even a single parameter, leads to an abnormallylow water quality value so that the selection of significantparameters should be carefully done and, in many cases, is onlyvalid for a given use. The water quality is not an absoluteconcept but is related to a predetermined concrete use. Theseprevious conditions must have been taken in mind for waterquality calculation.
Cabelli (1981) defined a water quality criterion developedthrough an indicator system as ‘a quantifiable relationshipbetween the density of the indicator in the water and thepotential risks of human health involved in the water’s use’.The development of a numeric criterion should aid to reducecontrol efforts by providing a clear numeric value to preventdiseases. The water quality criterion on health effects developedin this paper fits the above definition, and its purpose willbe to provide a quantifiable relationship which can be useful toset recreational water quality index for fresh bathing waters.
The World Health Organization (WHO) has been activelyinvolved in the protection of human health for the use ofrecreational waters. In 2003 and 2005, WHO published volumes1 and 2, respectively, of the Guidelines for Safe RecreationalWater Environments. The guidelines provide anassessment of the health risks associated with recreationaluse of water and outline linkages to monitoring and managementpractices. However, the selection of the ‘best’ indicatorto evaluate the relationship between water quality indicatorand swimming-associated illnesses is not obvious in freshwaterstudies. On the other hand, these guidelines for directcontactrecreational water are not developed to risk analysis;they were derived from a barely detectable health effect ratherthan from exposure-response data. Therefore, these guidelinesdo not allow decisions made by local, state or federal authoritieson health risks involved (Cabelli 1981).
Recreational water quality involves health hazards associatedwith recreational water use as well as aesthetic andnuisance conditions. Health hazards associated with directcontact with water include infections transmitted by pathogenicmicroorganisms as well as injuries and illness due tophysical and chemical properties of the water.
The main objective of this paper was to design a new recreationalwater quality index (RWQI) as a tool to ensure the health ofswimmers and to take practical decisions. It is importantwhentherisks of degradation ofwater quality due to agricultural,mining orindustrial practicesandhumanactivity exist.TheRWQIratings ofwater qualitywas developed using physical, chemical and microbiological parameters. Likewise, new sub-index rating curveshave been obtained to calculate the RWQI by means of a mathematicalexpression. To develop RWQI, the opinion from 17experts was employed by Delphi method.
This RWQI was elaborated with epidemiological data.An exhaustive study of the different guides for recreationalwaters proposed by different organisms around the worldwas carried out. In spite of the existence of a general waterquality index, it is important to obtain an index for therecreational waters. The judgment applied to the differentparameters should be appropriated to the use in question andmust be able to achieve a true relationship among healthrisks associated with recreational uses.
Uses and Limitation:
Categorization Table
Table 1 Descriptor word and RWQI (Recreational Water Quality Index ) numerical ranges
Standards Required
No standards required for this index calculation process.
Variables Selection
This index includes 12 variables for six water (public water supply, recreation, fish, shellfish, agriculture and industry) uses:
- pH
- Turbidity
- Detergents
- Nitrate
- COD
- PO43-
- Total coliforms
- coliforms
- coli
- Enterococci
Calculation of Recreational Water Quality Index :
RWQI (Recreational Water Quality Index) is calculated by the multiplication of all of the products of the parameter weights and sub-index values (QiWi)
Case Studies based on Recreational Water Quality Index
The index was applied to thedata set on water quality of the Potrero de losFunesRiver (San Luis, Argentina), generated during 2 years(2009–2010). Following the RWQI values classification,most of the Potrero de losFunes water samples fell inthe good quality range during the study period.