IMPACT OF SAND MINING ACTIVITIES ON THE QUALITY OF THE WATER

Abstract

Out of 103 number of rivers in Sri Lanka the 3n1 largest major river is Kaluganga. It hasthe highest volume of discharge as a percent (%) of precipitation per year out of the SriLankan rivers. It originates 4600m above mean sea level (Sripada), is 118km in lengthand opens to the sea at Kalutara.

At the lower reaches of Kaluganga is a densely populated zone where the inhabitants arehighly dependent on sand mining activities which adversely affect the quality of thewater in the river. To assess the extent of mining effects, six sites were selected. Out ofthose sites, water samples were collected for monitoring purpose samples were collectedfrom the Kethhena water intake. In the other five sites heavy sand mining activities areon going. To compare the variation of chemical, physical & biological parameters inwater, samples were collected from each site and analysed weekly for two months.

The physical parameters measured include - temperature, turbidity, suspended solids andelectrical conductivity. Chemical parameters assessed include pH, dissolved oxygen,BODs ( biological oxygen demand ), alkalinity, water hardness, [ Mg+2], [ Ca+2),[cr ]and COD. The data were analyzed by TWO WAY ANOVA using GLM procedureof MINITAB. Microscopic identification of biological parameters (phytoplankton's) wasidentified.

According to the results obtained, the value of pH, temperature and dissolved oxygen arein the desirable level. But some values like conductivity, suspended solids, turbidity,alkalinity, [Cl], [Fe], phosphates as P20s, COD are higher than the desired range. BODsis within desired which means low organic matter in the river. [Cl'] along the riverindicates the salt-water intrusion directly effected by mining lowering the river bed.[Mg2+], [Ca+2], Nitrogen, water hardness are lower than the desired level. Anabena,Nostoc, Microcystis, Closterium, Cosmarium, Occilatoria, Spirogyra. Spirulina Spps arcfound as biological indicators in the water at mining sites but in lower abundancy. At thesite of water intake few species were identified but abundancy is higher than in othersites. These species include, Occilatoria.Euglina ssp.,Closterium,Cosmarium,Spirogira

According to the above results it can be concluded that the sand mining activities hasadversely affected the quality of the water at the lower reaches of Kaluganga