Abstract:
Madu Ganga drainage basin covers an area of 700 acres and was designated
as a Ramsar Convention site in 2003. The main objectives of the research were
to assess the water quality in Madu Ganga and thereby identify its pollution
status. Water quality parameters, both physicochemical and biological, were
studied for a period of four months. Five sampling sites were selected from
the mouth of the estuary to the upper reaches of the river, namely Balapitiya,
Galmanduwa, Kothduwa, Kadapaunuduwa, and Wathugedara, primarily
based on ease of access. Physicochemical parameters, viz. water temperature,
pH, conductivity, DO, BOD5, COD, salinity, alkalinity as well as nitrate and
phosphate content were assessed. Biological parameters, viz. phytoplankton
and zooplankton densities, benthic macroinvertebrates (Littorina sp., mussels,
clams, red midge larvae, Penaeus indicus, Penaeus monodon, Metapenaeus
dobsoni, Macrobrachium rosenbergii), and most probable number (MPN
value) of E. coli bacteria were studied. The range of mean values of the above
parameters at five sampling sites was water temperature: 29 - 33 °C, pH: 7.20
- 8.32, conductivity: 0.8 - 21.3 mS, DO: 2.78 - 8.35 mg/L, BOD5: 8.08 - 10.63
mg/L, COD: 18.52 - 27.13 mg/L, alkalinity: 0.0005 - 0.0018 mg/L, salinity:
0.94 - 4.17 ppt, nitrates-: 0.05-0.45 mg/L, and phosphates: 0.007-0.029 mg/L.
Zooplankton density and phytoplankton density was 19-35 ind/ml and 22-48
ind/ml, respectively. MPN values were recorded below 10. Based on the
results of this preliminary study, Madu Ganga is polluted by E. coli bacteria,
and its water is saltier than pure freshwater, hence its water appears unsafe for
human consumption. It is recommended to have regular monitoring and
implement appropriate measures to reduce the extent of pollution in Madu
Ganga.
