IMPACT OF CATCHMENT CHARACTERISTICS ON NUTRIENT LOADING OF TWO DRY TROPICAL FRESHWATER LAKESANUYA VERMAAbstract The present study was an effort to investigate the influence of catchment characteristics on nitrogen (N) and phosphorus (P) loading and phytoplankton production in two freshwater lakes of Udaipur, Rajasthan. Most of the water quality variables, except total dissolved solids (TDS) and dissolved oxygen (DO), showed higher values in Lake Udaisagar compared to Lake Baghdara. Biological characteristics showed a general superiority of Lake Udaisagar with respect to phytoplankton density, chlorophyll-a biomass and primary productivity. With respect to the chemistry of bottom sediment, unlike N and P, organic-C in bottom sediment was high in Lake Baghdara due probably to allocthonous organic- C inputs from the woodland catchment. Phosphate-P declined markedly in Lake Udaisagar in winter 2001 due possibly to massive dredging and removal of P-rich upper sediment layer in dry periods of 2001. The study indicates that human activities in the catchment are important vector of N and P loading to tropical lakes; such inputs enhance phytoplankton growth; sediment dredging can be an effective tool for P removal and reversal of eutrophication in shallow tropical lakes.
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