The potential impact of new Andean dams on Amazon fluvial ecosystems

Abstract

Increased energy demand has led to plans for building many new dams in the western Amazon, mostly in the Andean region. Historical data and mechanistic scenarios are used to examine potential impacts above and below six of the largest dams planned for the region, including reductions in downstream sediment and nutrient supplies, changes in downstream flood pulse, changes in upstream and downstream fish yields, reservoir siltation, greenhouse gas emissions and mercury contamination. Together, these six dams are predicted to reduce the supply of sediments, phosphorus and nitrogen from the Andean region by 69, 67 and 57% and to the entire Amazon basin by 64, 51 and 23%, respectively. These large reductions in sediment and nutrient supplies will have major impacts on channel geomorphology, floodplain fertility and aquatic productivity. These effects will be greatest near the dams and extend to the lowland floodplains. Attenuation of the downstream flood pulse is expected to alter the survival, phenology and growth of floodplain vegetation and reduce fish yields below the dams. Reservoir filling times due to siltation are predicted to vary from 106-6240 years, affecting the storage performance of some dams. Total CO 2 equivalent carbon emission from 4 Andean dams was expected to average 10 Tg y . Mercury contamination in fish and local human populations is expected to increase both above and below the dams creating significant health risks. Reservoir fish yields will compensate some downstream losses, but increased mercury contamination could offset these benefits.

Protected areas: A focus on Brazilian freshwater biodiversity

“…These cases will demand international agreements to implement effective PAs, otherwise poor conservation policies in one country will jeopardize protection efforts in another. For example, the ongoing hydropower development in Peru, Colombia and Bolivia (Finer & Jenkins, 2012) will have negative effects on floodplain ecosystems and fish populations in Brazil (Forsberg et al, 2017;Latrubesse et al, 2017;Lees, Peres, Fearnside, Schneider, & Zuanon, 2016). The presence of these macro-river systems in Brazil indicates that conservation efforts will depend on transboundary policies.…”

Recent increase of river–floodplain suspended sediment exchange in a reach of the lower Amazon River

“…The hydrograph of the Amazon River has a trend of increased frequency of high annual peak and average flows and stable minimum flows in the past two decades (Gloor et al ., ), apparently associated with tropical Atlantic sea surface temperature trends. New hydroelectric power plants are operating or being built or planned on the headwaters and main lowland Amazon tributaries (Finer and Jenkins, ; Latrubesse et al ., ), which are expected to alter both flow regimes and sediment concentrations in the mainstem Amazon River (Forsberg et al ., ). Hence, we seek advances in data collection and modeling techniques to evaluate impacts of climate and catchment changes on regimes of flooding and sediment exchange between main channels and floodplains.…”

Ecosystem‐based management of Amazon fisheries and wetlands

“…There is the possible perception that protecting their spawning areas in western Amazon headwaters in Andean countries, where little commercial fishing occurs, would provide little benefit to the peoples that live there and only enhance downstream fisheries, including industrial‐scale operations in the Amazon River estuary where most of the commercial catch occurs. This perception, however, would be shortsighted because migratory fish species also provide the most solid scientific example for local peoples, NGOs and others to use as an environmental argument to confront the negative impacts of infrastructure development on western headwater sub‐basins that could have far‐flung downstream consequences on fisheries and wetlands in general (Forsberg et al., ). Mitigating the impacts of infrastructure on headwater sub‐basins would strengthen ecosystem services related in general to water quality, aquatic biodiversity and wetlands.…”