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The Project is composed by four subprojects, being developed simultaneously:


 1.  Online acquisition of micrometeorological and limnological data

The Integrated System of Environmental Monitoring – SIMA – is composed of hardware and software designed for the collection of data and the online monitoring of hydrological systems. For the acquisition of data, the SIMA uses an autonomous system anchored in the reservoir, composed of a toroid, where the sensors, storage electronics, battery, solar panel and transmitting antenna are set up. The data, collected periodically in pre-programmed intervals, are sent by satellite almost instantaneously to the user which may be up to 2500 km away from the sampling station. The combination of these abilities results in a powerful tool for the management and environmental control of water resources. This system was developed by a partnership between the University of Vale do Paraíba and INPE.
Since 1995 the project was transferred to Neuron Engenharia Ltda. Through a partnership with the Agency of Hydrography and Navigation (DHN), Neuron built a prototype of the SIMA, which was anchored in the coastal waters of Rio de Janeiro for a year, and the collected data were made available through the National Buoy Program. The data collected in this period were then compared with data collected in situ, confirming the good performance of the system. 


The selection of environmental variables to be monitored took into regard the following aspects:

  • its relevance for the characterization of aquatic environments
  • its relevance as an indicator of environmental impact (variables which respond very consistently to changes in the functioning of the aquatic environment)
  • its relevance to the processes of GHG emission
  • the technical viability of measurement by automatic platforms
Following these criteria, the automatic system of measurement is able to monitor the following variables:

  • water: water temperature, pH and turbidity, dissolved oxygen and CO2, conductivity, nitrate, ammonia, relative depth.
  • atmosphere: air temperature, atmospheric pressure, solar radiation, direction and intensity of wind, direction and intensity of currents. 
These variables are measured through a kit of sensors linked to the platforms. INPE is working alongside with the engineering team of Neuron towards the specification of sensors, the integration of the system and preliminary performance tests. These activities are taking place in the laboratory of mechanics and electronics of the program “Processes of the Hydrosphere”, from the General Coordination of Earth Observation (OBT) at INPE. All told there are 3 platforms, and it was necessary to acquire also two step kits to be employed in the maintenance of the system and to provide for possible changes of hardware.

Since it is a sophisticated equipment, the platform is carried from INPE to the study site by adequate transportation and packaging. Due to the weight of the platform, the transportation from the reservoir margin to the site of anchoring requires a large ship, which must be rented in advance.

The strategy of platform distribution considers both the safety of the experiment and the total period of sampling. The platforms must be anchored in a safe place, preferably close to the dam. The analysis of temporal series requires a large number of data in the same series, as well as the absence of missing values. Therefore, there must be one platform throughout the year in each studied reservoir. During the execution of the project there are visits to the platforms for maintenance and for the installation, for one week, of a trace gas analyzer. With this it is possible to establish, from the physical and biological viewpoint, the relationship between the processes in the water-atmosphere interface and the measured GHG flows (Lima, 2002).

In January of 2004 the two platforms were anchored at UHE Serra da Mesa and at APM Manso. In January of 2005 they were transferred to the UHEs Itumbiara ane Corumbá. In 2006 the platforms will operate in the UHEs L.C.B. de Carvalho and Mascarenhas de Moraes. In the beginning of 2007 one platform will be transferred to UHE Funil and the other to APM Manso. From 2004 to 2007 three field trips take place in each year, in the phases of rising waters (November), high waters (March) and drawdown (July).



2.  Estimates of Flows of CO2, CH4 and N2O in the water-atmosphere interface and in the water column


While the combustion of coal, oil or natural gas in thermoelectric power plants produces mainly carbon dioxide (CO2) through chemical oxidation, in hydroelectric reservoirs the main source of the gas is bacterial decomposition (both aerobic and anaerobic), producing mainly CO2, CH4 and N2O. The sampling of gas in the water-atmosphere interface, both as bubbles and through diffusion, is set up according to the region of the reservoir where the experiment takes place and to the depth of the chosen area. The samples are collected in the field in many different spots within the reservoirs, with funnels for the entrapment of bubbles rising from the bottom of the lake and through diffusion chambers which measure the vertical transport of diffuse gases. Profiles of methane concentrations in the water column are also measured. Each field trip demands approximately 7 days of work, the first and the last days being devoted to the transportation of the team to the reservoir and to setting up and dismounting the equipment. The team visits the reservoir twice in each day, in the morning and in the afternoon. Funnel sets are placed in areas with different depths in each studied reservoir, and the set remains for about 24 hours in each spot, in equilibrium with the water. After the funnels are set up the physico-chemical variables are measured and the experiments of gas diffusion as well as the profiling of CH4 take place. Basically, the sampling sets are placed in significant areas in the studied reservoirs, such as:

  • determine an emission pattern for very deep areas, where there was, presumably, biomass removal prior to the flooding);

  • presumably there was no biomass removal (the goal is to establish an emission pattern for shallow areas with intense biological activity);

  • opposed to the previous sampling (the goal is to determined similarities or differences in the pattern observed earlier);

  • (the goal is to determine an emission pattern in areas where the presence of a higher organic load influences the emission rates, as well as to evaluate the emission rate found before the flooding of the reservoir.

  • pattern in water coming from the turbines, originally from the deep areas of the reservoir).

As for the analysis, the best way to quantitatively estimate the gas concentrations found in the samples is the transportation of samples in adequate containers for later analysis in laboratory, through gas chromatography.

Elements of sampling:


The gaseous components (methane, carbon dioxide, nitrogen, oxygen and nitrous oxide) are quantified and the emission rates for each gas are calculated in each site, expressed in kg/km2/day.


For each studied reservoir the emission rates are combined with the percentage of each area to achieve the total emission rates of the reservoir.

We also measure, in situ, the gas flows, through a portable trace gas analyzer.


3. Carbon Cycle in the water column


Within aquatic environments, most of the carbon is present under the forms of dissolved inorganic and organic carbon. Particulate organic carbon represents around 10% of the total organic carbon and living organisms (biomass) are a small part of the particulate fraction. Particulate organic carbon in the form of detritus (necromass) is, in most cases, quickly mineralized, and so it contributes to the general pool of dissolved carbon. Just as the dominance of dissolved carbon in comparison with other forms is defined by biological activities (intense decomposition rates stimulated by high temperatures), the input (absorption) and output (emission) flows are also regulated by biogenic processes. The balance between the two flows is determined by the magnitude of the rates of respiration and primary/secondary production. The primary production converts inorganic carbon (CO2) in particulate organic carbon (biomass). Nevertheless, this process of primary production, through excretion processes that take place simultaneously with photosynthesis, transfers dissolved organic carbon from the cells to the environment. The secondary production is the work of heterotrophic bacteria which metabolize the dissolved organic carbon present in the environment and incorporate it, therefore, in the food chain. This ecological system of carbon transformation through the generation of biomass has, obviously, a high energetic cost. The respiration rates, expressed as the production of CO2, represent this cost. The analysis of ecological efficiency, expressed as the proportion between production and respiration, allows us to identify the main routes of carbon and the ecological status of the system. If the system acts predominantly as an incorporator of carbon (production is greater than respiration), it is considered as autotrophic. If, on the other hand, the system exports carbon (respiration greater than production), it is considered as heterotrophic. This identification of aquatic systems as autotrophic or heterotrophic is still a challenge for the aquatic sciences. Within this context, the evaluation of the biological processes, as well as the study of the energetic matrix involved – physical and chemical parameters) – is of paramount importance for the understanding of the carbon cycle and for the formulation of a model of this cycle, as well as of its implications in observed emissions.


Considering the above, the following data are being obtained: 

  1. Biological stocks of Carbon
    1. Phytoplanktonic biomass is obtained through analysis in inverted microscope, and the density is transformed to biomass through the measurement of the cell volume.
    2. Bacterial biomass is obtained through analysis in fluorescence microscope, and the density is transformed to biomass through an image analyzer.
  2. Carbon Transfer Processes
    1. Phytoplanktonic primary production is estimated through the incorporation rates of radioactive carbon (14C), according to Wetzel & Likens (1992).
    2. Organic carbon excreted by the phytoplankton is obtained through bubbling of the previously filtered sample in acid solution, for the evaluation of the intracellular incorporation of14C.
    3. Bacterial production is estimated through the incorporation of radioactive leucine [3H] with the centrifugation method proposed by Smith and Azam (1992). Incorporation rates are calculated according to the modified method of Bell (1993), originally established for the measurement of timidine incorporation, and converted directly as carbon production according to Simon and Azam (1989).
    4. Planktonic respiration – phytoplanktonic and bacterial – are measured simultaneously through a Micro-Oxymax respirometer, the oxygen uptake being measured through spectrophotometry as described by Roland et al. (1999). Plankton separation for the measurements of respiratory rates is achieved according to Cimbleris and Kalff (1998).
  3. Environmental parameters
    1. Such as concentrations of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC), total nitrogen, total phosphorus, concentration of chlorophyll-a; 13C of dissolved CO2 and CH4 and 13C and 15N of the POC, aiming at distinguishing allochthonous and autochthonous material, are determined according to different methods. Limnological variables – pH, dissolved oxygen, electric conductivity, turbidity and temperature – are measured in situ.
  4. Quantification of input of allochthonous material
    1. The main tributaries of each reservoir are identified, and sampling sites are determined for the measurements of the concentrations of DOC and POC (mg/L). The organic load is then estimated through the measurement of the drainage areas referring to each sampling site, and through the use of average daily flow, registered in fluviometric stations present in the basins of the reservoir. The work is developed with geographic charts at the 1:50.000 scale, where the sampling sites are chosen, aiming at outlining and measuring the respective drainage areas. The average daily flows, obtained in the same day when the sampling took place, are taken from fluviometric stations, from which the drainage areas are known. After that, the specific load (liters per second per square kilometer) is estimated and multiplied by the drainage area of the sampling site. The concentrations of DOC and POC are also evaluated immediately downstream of each reservoir.


 4. Estimate of Flows of CO2, CH4 and nitrogen (N2) in the water-sediment interface

A large portion of greenhouse gases results from the decomposition of organic matter present in anoxic sediments, which are therefore one of the main components in the transformations of carbon and nitrogen in aquatic systems. Sediments are collected (Adams, 1994) in places close to the sampling sites of water column and surface, and the concentration of the following gases are measured in the interstitial water: CO2, CH4, N2, oxygen (O2) and argon (Ar). The samples, kept within the sampling apparatus, are preserved in bags filled with helium gas (Fendinger & Adams, 1986), and, in intervals between 1 and 2 cm, transferred to a system of syringes adapted to it. These syringes are then stored in bags with helium and kept in ice until the analysis of the gases is performed, through gaseous chromatography, between 24 and 48 hours after the sampling. The measurements of oxygen and argon are used as indicators of atmospheric contamination of the samples. The argon is also used for the enhancement of the performance of N2 measurement. The diffusive flows of CO2, CH4, and N2  are quantified in the sediments and in the interface water-sediment, so as to evaluate the loss of these gases to the water column and its potential of deoxygenation and denitrification of hypolimnetic waters, as well as the flow to the atmosphere. The isotopic composition of carbon and nitrogen in the sediments are also analyzed.


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