APPLICATION OF WATER QUALITY INDEX TO ASSESS THE SITE SUITABILITY FOR MARICULTURE

An attempt has been made to assess the  seasonal Water Quality Index (WQI) using fourteen surface water quality parameters including SST, pH, salinity, dissolved oxygen, biochemical oxygen demand (BOD), Chlorophyll-a, nitrate-nitrogen, nitrite-nitrogen, phosphate, ammonia-nitrogen, turbidity,  total suspended  solids (TSS), total dissolved  solids  (TDS) and  silicates measured  at  five  different  stations  in  the  creeks  and  nine  near  shore  areas  along  the Maharashtra coast during the year 2014 to 2016. Rating scale is developed from mariculture and coastal aquaculture point of view. The WQI were computed using Weighted Arithmetic Water Quality Index Method (WAWQI).

The  overall  surface  water  quality  was  graded as "Very Poor" for creek stations and "average or  poor"  for  near  shore  stations  located  in densely    populated    area    along    Mumbai. However,   sampling   stations   of   moderately urban area along  Ratnagiri  coast  in  southern Maharashtra   rated   as   "average   or   Poor". Season-wise high-water   quality index   value for   near   shore   stations   and   creek   stations reported during monsoon and post-monsoon period respectively.  The water quality index ranges from 133.  056  (monsoon)  to  842.12 (post-monsoon)  at  10  m  station  off  Mumbai and near shore station at Juhu beach, Mumbai respectively.  The  high  value  of  water  quality index     reported     mainly     due     to     higher concentrations of phosphate, nitrate, nitrite and poor  dissolved  oxygen  content  in  creek  and nearshore areas. The main cause of poor water quality  is  associated  with  discharge  of  semi- treated sewage, urban runoffs, illicit discharge of  industrial  effluent  directly  into  the  creek and  nearshore  areas.  The application of the developed water quality index for mariculture in selected location showed that water quality of near shore stations in southern Maharashtra is favourable for mariculture than the station in northern part. The Weighted Arithmetic Water Quality  Index  could  be  a  good  measure  for categorizing      ideal      water      quality      for mariculture  or  coastal  aquaculture.  Owing to its rapid interpretation of data, it can be a good tool    for    water    quality    management    and planning    for     coastal    zone     management including mariculture.