Preliminary assessment of dam hydrological effects in the Brazilian Pantanal

Abstract

The Pantanal is the world's largest tropical wetland, comprising c.150,000 km⠯f lowland floodplain in the Paraguay River basin. Its habitat diversity and climatological conditions support high biodiversity, including the richest wetland avifauna in the world. Recent increases in human activities in the region have raised concern about potential environmental impacts, especially impacts of dam building in the basin's highlands. In this paper we assess the hydrological effects of APM Manso Dam, 10 years after its initial flooding (1999), specifically the magnitude and timing of median annual maximum and minimum flows. Flow changes were assessed at 13 downstream gauging stations on the Manso, Cuiabᠡnd Paraguay rivers, with consideration of the influence of climatic variability through the assessment of two nearby unaffected gauging stations over the same time frame. Preliminary results suggest that changes in magnitude of 1-day minimum flows occurred as far as 266 km downstream of APM Manso Dam, reaching the city of CuiabᮠChanges in the timing of 1-day minimum and in the magnitude of 1-day maximum discharges are potentially reaching the city of RosᲩo Oeste, c. 122 km downstream of APM Manso Dam. Shift in the timing of 1-day maximum is limited to Manso River reaches. No clear alterations could be found at the heart of the Pantanal lowlands, which is located c. 400 km downstream of APM Manso dam. Further analysis is in progress, considering a larger set of flow statistics, including ecologically relevant hydrological statistics from IHA (Indicators of Hydrological Alteration) and RAP (River Analysis Package). Future studies on the ecological impacts of the dam will be based on this analysis of hydrological alterations in the Manso, Cuiabፊand Paraguay rivers.