Studies on Nutrients of Mandovi & Zuari River Systems

Abstract

Seasonal cycle of nutrients was related to rainfall and application of agricultural fertilizers in the low lying areas. The stations at the marine-end showed 2 peaks in nitrate and phosphate corresponding to monsoon and postmonsoon seasons, while the stations at the river-end showed only monsoon peak. Silicate showed a well-defined pattern of distribution with only one peak during monsoon. Applying 'simple mixture' relations using salinity as indicator, it was observed that in premonsoon nitrate, phosphate and silicate were removed from the water but during monsoon only phosphate was removed while nitrate and silicate showed a near-conservative behaviour. In post monsoon there was a net addition of nitrate and phosphate while silicate showed 50% loss.