Water quality impacts of small hydroelectric power plants in a tributary to the Pantanal floodplain, Brazil

Abstract

Small hydroelectric power (SHP) facilities are proliferating around the world, including in Brazil where legislation encourages SHP over other hydropower development, defining SHP as facilities with installed capacities of 3–30 MW and reservoirs <13 km2. SHP facilities are often diversion designs with small or no reservoirs, while other SHPs have more conventional dams that create extensive reservoirs. This study seeks to understand the relative impacts of these two different designs on downstream water quality, comparing a conventional SHP system on the main stem to a complex of smaller SHPs with diversion designs in lower‐order reaches of the São Lourenço River. This river delivers nutrients and sediments to the Pantanal, one of the world's largest floodplain ecosystems. Samples collected upstream and downstream of each set of facilities over a range of flows revealed that the conventional SHP reservoir significantly reduced pH, dissolved oxygen, total iron, suspended solids, and turbidity consistent with observations in many other reservoirs. In contrast, water quality changes downstream of the smaller SHPs were less pronounced and could be attributable to natural variability. An analysis of energy production versus water quality impacts suggests that SHPs on the smaller tributaries are favorable compared to the conventional SHP in terms of water quality impacts. With the proposed addition of dozens of new facilities in the upland watersheds draining into the Pantanal, this study improves our understanding of the relative impacts of different designs of SHPs on downstream water quality, while recognizing that water quality is just one of several potential impacts to be considered.

Passive Acoustic Monitoring of Chaco Chachalaca (Ortalis canicollis) Over a Year: Vocal Activity Pattern and Monitoring Recommendations

“…We also provide the most effective sampling periods for monitoring the species, which might be useful for traditional or passive acoustic surveys, and an estimate of the number of days to record a reliable detected vocal activity rate of the species, which might be used for monitoring population abundance changes over time. The use of passive acoustic monitoring for detecting wildlife presence or estimating population trends over time might be especially well suited for monitoring the environmental status of the Pantanal wetland, which is under threat (e.g., Tomas et al, 2019; da Cruz et al, 2021). Indeed, this tool might be especially useful for performing continuous surveys in inundated areas, as we did in the present study, since wildlife monitoring during this period might be an extra challengue to tropical bioacoustic surveys.…”

Factors associated with the population structure of an invasive mollusk in a neotropical floodplain

“…These results are likely explained by the preserved state of the Ivinhema River because it is situated into a permanent preservation park (Braghin et al 2018). As a result, the Ivinhema River maintains the most pristine abiotic filters, such as high turbidity and suspended inorganic matter (Table S5), which are characteristic of the Upper Paraná Floodplain (Agostinho et al 2004a) and many other floodplains (da Cruz et al 2021;Melack et al 2021;Molinari et al 2021;Nogueira et al 2021).…”

Hydropeaking by Small Hydropower Facilities Affects Flow Regimes on Tributaries to the Pantanal Wetland of Brazil

“…In light of the ongoing construction and planning of future SHPs in the Pantanal watershed, there is an urgent need to understand how numerous SHPs on the tributaries may, in aggregate, alter the transport of water, sediments, and nutrients from the uplands into the Pantanal, and as well produce enough barriers to the upstream migration of fishes from the Pantanal to impede their reproduction and reduce their populations. In recognition of these needs, the present study is part of a multidisciplinary research program that has examined many dimensions of the issues surrounding hydroelectric facilities in the tributaries of the Pantanal, including hydrology (this study), sediment transport (Fantin-Cruz et al, 2020), water quality (Oliveira et al, 2020;Fantin da Cruz et al, 2021), and fish and fisheries (Campos et al, 2020;Ely et al, 2020). In this study, evidence for hydropeaking is evaluated based on discharge patterns in river gages downstream of 11 reaches containing a total of 24 hydropower facilities compared to simultaneous measurements at reference gages not influenced by the facilities.…”