Temporal,Spatial and Depth Variation of Nutrients and Chlorophyll Content in an Urban Wetland

The Deepor Beel is a permanent, freshwater lake at the southwest corner of Guwahati in the southern bank of the Brahmaputra River and the Beel serves as the major storm water storage basin for Guwahati city. It is recognized as a Ramsar site (No. 1207) in 2002. The water quality of the Beel is threatened in recent times by excessive fishing activities, hunting of water birds, pollution from pesticides and fertilizers, and infestation by water hyacinth Eichhornia crassipes. The present work reports on bimonthly monitoring of macro and micro nutrients including nitrate, phosphate, potassium, boron, copper, iron, zinc at 13 different sites and three different depths of the water column. The impact of the nutrients on chlorophyll (a, b and c) contents of the wetland were also monitored. Each parameter was monitored 202 times in total. The measured values were subjected to analysis of variance test, which indicated important temporal, spatial and depth-wise correlations for the parameters. The ratios of total nitrogen to total phosphorus for the water is mostly <10 and the Trophic State Index is >70.0, both of which point to a phosphorus-enriched state and water approaching eutrophic conditions. The results indicate a serious degradation in quality of the water mostly due to human interferences.