SPATIAL DEPENDENCE OF RESERVOIR TROPHIC STATES IN THE JAGUARIBE RIVER BASIN

Código

V-END_II-EBHE0053

Autores

Kaillan Marreiro de Sousa, Jeniffer Johana Duarte Sanchez, Gualberto Segundo Agamez Montalvo

Tema

18 - Aspectos qualitativos de água em situações de desastre

Resumo

This study analyzes the spatial connection of water quality degradation across interconnected reservoirs in the semi-arid Jaguaribe River basin, Brazil. Given that trophic state indices are recorded as ordinal categories, we implemented a latent-variable framework to generate pseudo-continuous data, enabling the application of flexible copula functions. Pairwise and multivariate C-vine copulas were fitted to quarterly data spanning from 2008 to 2025 across six strategic reservoirs. The empirical findings indicate a highly synchronized pattern of environmental degradation along the primary hydrological channel, with the Orós?Castanhão system exhibiting the most robust association. Conversely, marginal tributary reservoirs displayed weak or negligible spatial dependence. Stochastic simulations revealed a high probability of widespread, concurrent eutrophic states throughout the main river network, while extreme joint hypereutrophic events remained rare. Furthermore, the conditional vine model confirmed that downstream connectivity persists even when accounting for upstream regulation. This framework addresses the statistical challenges of ties in categorical environmental indicators. From a water resource management perspective, the results emphasize the role of major downstream reservoirs as strategic indicators for basin-wide ecological status.