Giant otter behaviour in a mega-hydroelectric reservoir, Central Amazon, Brazil

We tracked thirteen giant otters from three different groups in the Balbina Hydroelectric Reservoir. One of them was a transient animal, while the others were living in groups of five and seven individuals. Travelling was the most frequent behaviour, both for the transient otter (>40%) and group otters (46%). Diurnal resting was the longest-lasting behaviour. Most giant otter behaviour in the reservoir showed little difference when compared with the behaviour of giant otters living in nondammed areas, indicating a significant degree of resilience of this species. However, otters in the reservoir spent more time travelling, probably because their territory sizes were much greater than the territories of giant otters in nondammed areas. The frequency of fishing was similar to what has been recorded elsewhere, suggesting that current fish density and availability in the reservoir is similar to what is observed in nondammed areas. Nevertheless, otters in Balbina spent more time fishing than those in nondammed areas, which alternatively could suggest that fish density in the reservoir was low and could be compensated by increasing the time spent fishing. The high frequency of intraspecific kleptoparasitism observed in this study (62%) is noteworthy, although virtually undocumented for this species. This is the first study of giant otter behaviour in a hydroelectric reservoir that can be used for the conservation of this endangered species in man-made lakes.

Unaccounted CO2 leaks downstream of a large tropical hydroelectric reservoir

Recent studies show that tropical hydroelectric reservoirs may be responsible for substantial greenhouse gas emissions to the atmosphere, yet emissions from the surface of released water downstream of the dam are poorly characterized if not neglected entirely from most assessments. We found that carbon dioxide (CO2) emission downstream of Kariba Dam (southern Africa) varied widely over different timescales and that accounting for downstream emissions and their fluctuations is critically important to the reservoir carbon budget. Seasonal variation was driven by reservoir stratification and the accumulation of CO2 in hypolimnetic waters, while subdaily variation was driven by hydropeaking events caused by dam operation in response to daily electricity demand. This “carbopeaking” resulted in hourly variations of CO2 emission up to 200% during stratification. Failing to account for seasonal or subdaily variations in downstream carbon emissions could lead to errors of up to 90% when estimating the reservoir’s annual emissions. These results demonstrate the critical need to include both limnological seasonality and dam operation at subdaily time steps in the assessment of carbon budgeting of reservoirs and carbon cycling along the aquatic continuum.

Understanding how hydrological forecast quality impacts the management of hydroelectric reservoirs

<p>The evaluation of inflow forecast quality and value is essential in hydroelectric reservoir management. Forecast value can be quantified by the economic gains obtained when optimizing hydroelectric reservoir operations informed by weather and hydrological forecasts. This study [1] investigates the impact of 7-day streamflow forecasts on the optimal management of hydroelectric reservoirs and the associated economic gains. Flows from ten catchments in France are synthetically generated over a 4-year period to obtain forecasts of different quality in terms of accuracy and reliability. These forecasts define the inflows to ten hydroelectric reservoirs, which are conceptually parametrized. Each reservoir is associated to a downstream power plant with yield 1 which produces electricity valued with a price signal. The system is modelled using linear programming. Relationships between forecast quality and economic value (hydropower revenue) show that forecasts with a recurrent positive bias (overestimation) and low accuracy generate the highest economic losses when compared to the reference management system where forecasts are equal to observed inflows. The smallest losses are observed for forecast systems with under-dispersion reliability bias, while forecast systems with negative bias (underestimation) show intermediate losses. Overall, the losses (which amount to millions of Euros) represent approximately 1% to 3% of the revenue over the study period. Besides revenue, the forecast quality also impacts spillage, stock evolution, production hours and production rates. For instance, forecasting systems that present a positive bias result in a tendency of operations to keep the storage at lower levels so that the reservoir can be able to handle the high volumes expected. This impacts the optimal placement of production at the best hours (i.e. when prices are higher) and the opportunity to produce electricity at higher production rates. Our study showed that when using biased forecasting systems, hydropower production is not only planned during more hours at lower rates but also at hours with lower median prices of electricity. The modelling approaches adopted in our study are certainly far from representing all the complexity of hydropower management under uncertainty. However, they proved to be adapted to obtaining the first orders of magnitude of the value of inflow forecasts in elementary situations.</p><p>[1] https://doi.org/10.5194/hess-2020-410</p>

Influência da precipitação e a temperatura na dieta de lontra [(Lontra longicaudis (Olfers, 1818)] em área de influência de reservatório hidrelétrico no rio Jari, Amapá, Brasil

Foi avaliada a dinâmica sazonal da precipitação e da temperatura na dieta de Lontra longicaudis nas áreas de influência direta e indireta do reservatório Hidrelétrico Santo Antônio do Jari, Amapá, Brasil, para testar a hipótese do predomínio de itens de peixes no total de fezes e o aumento de itens de crustáceos e da diversidade de presas no período menos chuvoso. O estudo foi realizado na Usina Hidrelétrica Santo Antônio do Jari (UHE) localizada cerca de 150 km da foz do rio Jari com as coletas de fezes a cada trimestre durante 2016, 2017 e 2018 na montante e jusante dos rios em período chuvoso e período menos chuvoso, e os itens alimentares encontrados foram quantificados para cada categoria alimentar por meio da frequência de ocorrência relativa (FOr%) e calculada a média e o desvio padrão. Para verificar a relação entre a frequência alimentar e as variáveis climáticas foi realizada a ordenação por meio da Análise de Componentes Principais (PCA) com a auxílio do software estatístico R. Em 542 amostras de fezes analisadas, os peixes e crustáceos foram as classes mais consumidas ao longo dos três anos principalmente na jusante. Houve correlação positiva entre itens de peixes e precipitação, e itens de crustáceos temperatura. As informações obtidas são fundamentais como indicadoras ambientais para o manejo e conservação de lontra em ambientes naturais/ou impactados, principalmente quando associados com os aspectos climáticos na região amazônica. Precipitation and temperature as environmental indicators in the Neotropical Otter diet [(Lontra longicaudis (olfers, 1818)] in an area of influence of a hydroelectric reservoir on the Jari river, Amapá, Brazil A B S T R A C TWere evaluated the seasonal dynamics of precipitation and temperature in the Lontra longicaudis diet in the areas of direct and indirect influence of the Santo Antônio do Jari Hydroelectric Reservoir, Amapá, Brazil, to test the hypothesis of the predominance of fish items in the total of feces and the increase of crustacean items and the diversity of prey in the less rainy period. The study was carried out at the Santo Antônio do Jari Hydroelectric located about 150 km from the mouth of the Jari River with the collection of feces every quarter during 2016, 2017 and 2018 in the upstream and downstream rivers in the rainy season and less rainy season, and the food items found were quantified for each food category using the frequency of relative occurrence (FOr%) and the mean and standard deviation were calculated and to check the relationship between food frequency and climatic variables, ordering was performed by means of of Principal Component Analysis (PCA) with the aid of the statistical software R. In 542 samples of feces analyzed, fish and crustaceans were the most consumed items over the three years, mainly upstream. There was a positive correlation between fish items and precipitation, and temperature and crustaceans items. The information obtained is fundamental as environmental indicators for the management and conservation of otters in natural / or impacted environments, especially when associated with climatic aspects in the Amazon region.Keywords: Otter, environmental factors, diet, dam.

Pengelolaan Daerah Tangkapan Air Waduk Pembangkit Listrik Tenaga Air (PLTA) Koto Panjang Berkelanjutan

Riau Province has many lakes and reservoirs, one of which is the Koto Panjang Hydroelectric Reservoir, Sustainability of the Koto Panjang Hydroelectric Reservoir Unstable water continuity, drought during the dry season and flooding during the rainy season have caused this power plant to be not optimal, one of the ways that can done to overcome complications in certain areas. Koto Panjang Hydroelectric Reservoir Water is that by using the analysis of the Koto Panjang Hydroelectric Reservoir we can arrange steps in managing the maintenance of the Koto Panjang Hydroelectric Reservoir. Sustainability analysis conducted using the RAP-catchment area application on three dimensions, namely ecology, economics and social, the results of the analysis that have been carried out on the ecological dimension address an index of 52.31 which is classified as quite sustainable in the social dimension category 41.98 which is classified as less sustainable. To improve the index of sustainability in the management of water areas, several management directives are needed, namely reforestation or greening of open land related to rivers and conducting training in environmentally friendly agriculture to provide and support the protection of farming communities and communities related to fire, develop the potential of natural resources such as tourist attractions as alternative livelihoods to increase community income and increase socialization and encourage people in need in hydropower reservoir catchment areas.

High organic carbon burial but high potential for methane ebullition in the sediments of an Amazonian hydroelectric reservoir

Reservoir sediments sequester significant amounts of organic carbon (OC), but at the same time, high amounts of methane (CH4) can be produced and emitted during the degradation of sediment OC. While the greenhouse gas emission of reservoirs has received a lot of attention, there is a lack of studies focusing on OC burial. In particular, there are no studies on reservoir OC burial in the Amazon, even though hydropower is expanding in the basin. Here we present results from the first investigation of OC burial and CH4 concentrations in the sediments of an Amazonian hydroelectric reservoir. We performed sub-bottom profiling, sediment coring and sediment pore water analysis in the Curuá Una (CUN) reservoir (Amazon, Brazil) during rising- and falling-water periods. The spatially resolved average sediment accumulation rate was 0.6 cm yr−1, and the average OC burial rate was 91 g C m−2 yr−1. This is the highest OC burial rate on record for low-latitude hydroelectric reservoirs. Such a high rate probably results from a high OC deposition onto the sediment, which compensates the high OC mineralization at a 28–30 ∘C water temperature. Elevated OC burial was found near the dam and close to major river inflow areas. C:N ratios between 10.3 and 17 (average ± SD: 12.9±2.1) suggest that both land-derived and aquatic OC accumulate in CUN sediments. About 23 % of the sediment pore water samples had dissolved CH4 above the saturation concentration. This represents a higher share than in other hydroelectric reservoirs, indicating a high potential for CH4 ebullition, particularly in river inflow areas.