RESUMO
A systematic study was carried out over all the seasons for two consecutive years (March 2003 to May 2005) to monitor the most important physico-chemical parameters of the Siang river water, Arunachal Pradesh, India in order to establish the baseline data of the river water. Water samples were collected from nine locations covering a stretch of 45 km of the river, in and around Pasighat, the district headquarters of East Siang District, Arunachal Pradesh. Alarge number of parameters such as temperature, pH, electrical conductivity, total solids, total dissolved solids, total hardness, dissolved oxygen, chlorides, sulphates, phosphates, silicates, bicarbonates, sodium, potassium, calcium and magnesium were found to be well within the permissible limits for drinking water. Concentration of iron is very high in the study stretch, but all other metals were well below the maximum permissible limits. Levels of metals such as Cu, Co, Cr, Mn, Ni, Pb and Zn are attributed to lithogenic contribution in absence of industrial and large scale agricultural activity in the study area.