ENVIRONMENTAL INDICES

1. ENVIRONMENTAL INDICES

2. DEFINITION • It is a numerical or descriptive categorization of a large quantity of environmental data or information with the primary purpose being to simplify such data and information so as to make it useful for decision makers and various publics • To summarize existing environmental data • To communicate information on quality of affected environment • To evaluate the vulnerability or susceptibility of an environmental category to pollution • To focus attention on key environmental factors • To serve as basis for the expression of impact

3. BACKGROUND INFORMATION • Env. Index differs from Env. Indicators • Indicators- definition • Eg – Plant species –Grazing (Odum, 1959) • E.Indicator – useful tools for monitoring the state of the env. In relation to sustainable development and associated env. threats • Importance points to be considered for selecting E.I • Steno species are better than Eury • Large species usually make better indicators than small species • Before selecting species – field evidence, lab evidence. Also the species ability to compensate or adapt should be known • Arriving numerical relationship make them reliable indicators –MPN coli form

4. EI- Air quality • Indices • Number of indices were developed • A common Pollutant Standards Index was developed • Ten criteria were delineated for PSI • Be easy to understand – include major pollutant and future pollutant-relate ambient air quality standard- relate to air pollution episode criteria – be calculated in a simple manner using reasonable assumption – be based on a reasonable scientific premise – be consistent with perceived air pollution levels – be spatially meaningful- exhibit day to day variation – enable forecasting a day in advance.

5. EI- Air quality • PSI is established by defining an index value of 100 as the equivalent of short term air quality standards. • PSI is based on health effects • The sub index is calculated as follows Conc. Of pollutant Subindex = -------------------------------- (100) short term primary std.

6. EI- Water quality • WQI is based on DELPHI APPROACH- utilize the expertise of 142 resource person • 3 questioner each for a member • Q.1 RESPONDENTS WERE ASKED TO CONSIDERED 35 WATER POLLUTANT – FOR POSSIBLE INCLUSION IN WQI • 2 type of response for each pollutant • First – designate the pollutant – DNI, I and UD • Second – rating the pollutant (scale 1-5) • Q.1 RESULTS ARE TABULATED AND SENT BACK TO MEMBERS WITH Q.2 • Asked to review of their previous designation and rating • Following receipt of Q.2 –Individual important items are identified • DO, coli forms, pH, BOD, NO3, PO4, temperature deviation, Turbidity, TS • Q.3 ASKED TO DEVELOP A RATING CURVE FOR EACH OF THE VARIABLES • X axis – strength of the pollutant, Y axis = Levels of water quality (0-100) • Asked to draw a curve – Investigators averaged the curves and produce average curves for each pollutants • Solid line represents arithmetic mean of all respondents curve • Dotted line bounding shaded area – 80 percent confidence limits • A narrow band of shading denotes greater agreement - DO graph • Broad one - Turbidity

8. WQI – Calculation • Calculation of WQI is based on weighed linear sum of subindices (WQIa) or a weighted product aggregation function (WQIm) can be used. • Wi = importance weight assigned to variables • These are expressed mathematically as follows • NSF WQIa = • NSF WQIm =

9. STEPS IN THE APPLICATION THE WQI • Assemble average and extreme data for each parameter • Use figures to determine Ii for average and extreme conditions • Calculate WQIa and/or WQIm for average and extreme conditions and interpret the results as appropriate