TY - JOUR AU - Sofia MG Rocha, AU - Maria de JD Rocha, AU - Germário M Araújo, AU - Helena Becker, AU - Iran E Lima Neto, PY - 2022/07/27 Y2 - 2024/03/28 TI - Seasonal and interannual variability of residence time and total phosphorus in a small hypereutrophic lake in the Brazilian northeast JF - Water SA JA - WSA VL - 48 IS - 3 July SE - Research paper DO - 10.17159/wsa/2022.v48.i3.3893 UR - https://watersa.net/article/view/14442 SP - AB - <p>This study evaluates the residence time (RT) and total phosphorus (TP) in a small hypereutrophic lake in the city of Fortaleza, Brazil. The results indicate that RT predicted by a complete-mix model is very similar (<em>R</em>² = 0.83) to that simulated with a 2-D hydrodynamic model (CE-QUAL-W2). Simple power-laws were fitted to describe RT and TP concentration at the lake inlet as functions of lake inflow, yielding correlations of <em>R</em>² = 0.84 and 0.70, respectively. The combination of these correlations with a complete-mix approach provided a comprehensive model that predicted TP values measured at the lake outlet reasonably well (<em>R</em>² = 0.60). In addition, a direct empirical correlation between simulated TP concentration and precipitation was also obtained. The simulations indicate a nearly periodic behaviour of RT and TP, with the seasonal variations being much higher than the interannual ones. Finally, an application of the model showed that a reduction of 99% of the input TP load was required to reach 100% compliance with the required water quality standards; this could be achieved by connecting the residences to the sewage network. The methodology proposed in this research can be easily applied to other lakes in the Brazilian northeast and extended to other tropical regions around the globe.</p> ER -