Estimating Sediment-water P exchange in Lake Rio Verde (Paraná State, Brazil)

Document Type: Original Research Paper

Authors

1 SANEPAR Water and Sanitation Company of Paraná State, Rua Eng. Antonio Batista Ribas, 151, Rebouças, Zipcode 82800130, Curitiba, Brazil

2 UNESCO-IHE Institute for Water Education, PO Box 3015, 2601 DA Delft, The Netherlands

Abstract

Monthly and annual water and phosphorus mass budgets were set up over the year 2010 for the
Lake Rio Verde, Brazil. Limited data for the water budget was compensated using an interpolation method
with data water budget data of a nearby reservoir. Thus, errors of ca. 1.5% were estimated for the water
budgets. Dominant P mass input terms were inflows from the rivers and direct run off into the reservoir. Main
output terms were P outflow via rivers and industrial water abstraction. Equalizing the P inputs and outputs
leads to a sediment phosphorus uptake term were estimated at 35% of the annual P inflow, but with a possible
weak correlation between monthly P sediment/water exchange and monthly precipitation figures. Sediment
characteristics likely play an important role in the P sediment-water exchange. High concentrations of P in
sediment pore water, and seasonal reductions in the oxidized surface layer of sediment suggests reduction of
the potential of the sediment to retain P under current and likely, increased, P loads to the reservoir. Future
management of the reservoir, therefore, requires continued monitoring and catchment management to mitigate
nutrient both point source and diffuse loads. This necessitates an integrated approach to reduce pressures on
the reservoir. Failure to address potential problems can lead to reduced water quality, with associated increased
treatment costs for water supply.

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