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Nutrient load concept- reservoir vs. bay
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F., Matta, E., Hinkelmann, R. & Gunkel, G.
||Proceedings 17th IWA-DIPCON Conference, Berlin, Germany.
water bodies possess environmental gradients and monitoring programs
are mostly adapted for cost and time effectiveness. Bay areas are
often more isolated from the main water body and are likely to have
unobserved different environmental processes and impacts. This study
was performed at the Itaparica reservoir, São Francisco river,
located in semi-arid Northeast Brazil, with dendritic form. Since
water exchange of a bay is difficult to measure, flow and transport
simulations were performed for bay water residence time estimation.
The P-chlorophyll a relationship was used to develop the P use
efficiency model for critical P load estimation of 25 µg P L-1.
Phosphorus sources and input rates into a bay and the respective
reservoir were calculated and compared regarding their different
origins for the period after damming and for 2013. After impoundment,
the P load highly exceeded the carrying capacity, because of leaching
and mineralization processes. In 2013, P inputs were still above this
threshold, whereas inflow and sub-basin P export during the rainy
season were crucial. But eutrophication processes have increased in
the bay relative to the main water body. Hence, water quality is
mainly seasonally degraded leading to a need for watershed
conservation measures to reduce eutrophication processes.