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Water Resources

.Understand how Cemig uses water resources in its plants, which use only water as their raw material.

Did you know that one of the largest fresh water reserves in the world is concentrated in Brazil? The surface waters generated in our territory represent about 50% of the total resources in South America and 11% of the world resources.

Here at Cemig, we make use of water resources to generate electricity through our hydroelectric power plants, whose raw material is 100% water. This water used to generate energy is not consumed: it passes through the turbines and returns immediately to the river, following its natural course.

The reservoirs built to accumulate water to generate electricity help to regulate water availability in the river basin. They provide higher flows during periods of drought or water crisis and minimize flooding during the rainy season.

Weather forecasting and constant monitoring of rain and water level in reservoirs and rivers are fundamental for managing the storage volume of hydroelectric power plants. To assist us, we have a wide network of automatic measuring stations, which send data in real time so that the planning of the gates operation and power generation is optimized.

Apart from the advantages of regularization, the water stored in the reservoir can also be used for other purposes such as:

  • Human and Industrial Supply;
  • Irrigation;
  • Navigation;
  • Fishing and Aquaculture (rearing fish in net-tanks);
  • Tourism and Leisure, offering benefits to the river basin.

To promote the sustainable use of water, our technical team is constantly seeking improvement through specializations, master’s and doctorate degrees, training, participation in national and international seminars and in Research and Development – R&D projects with ANEEL 


In Brazil, since the establishment of the National Water Resources Policy and the National Water Resources Management System with the publication of Law No. 9,433 in 1997, water use has been discussed in collegiate Water Resources Management Bodies with the participation of public authorities, civil society and users.

The water resources management involves a set of actions aimed at regulating its use, control and protection, in accordance with the relevant legislation and regulations. This legislation is elaborated by the legislative and executive powers, and by collegiate and deliberative bodies that make up the National and State Water Resources Management Systems.

Due to its use of water, Cemig participates in an active and strategic way in the formulation of laws and norms of the Water Resources Management Policy and System. The company is present in the technical discussions of the main collegiate bodies for the formulation of rules and the establishment of guidelines, such as:

  • the National Water Resources Council (CNRH);
  • the State Water Resources Council (CERH);
  • the Federal and State River Basin Committees;
  • the Technical Chambers;
  • the Working Groups, especially those dealing with the preparation of master plans for water resources, the regulations on Granting and Collection for the Use of Water Resources.

Therefore, we represent the users of water resources for hydroelectric power generation in the State Water Resources Council in the State of Minas Gerais (CERH/MG), in 04 river basin committees of the Federal Government and 20 river basin committees of the State Government.  

In our Water Resources Policies, learn more about how water is managed and conserved in our energy generation processes.

River Basin Committees

The River Basin Committees are management groups composed of representatives of the three levels of government (federal, state and municipal), water users and civil society. It is through democratic discussions and negotiations that these committees assess the real and different interests in river basin water uses.

The main decisions made by the committee are:

  • Approve and monitor the development of the Basin Water Resources Master Plan, which gathers strategic information for water management in each basin;
  • Mediate conflicts for the use of water (in the first administrative instance);
  • Establish mechanisms and suggest charging amounts for the use of water.



Water quality monitoring (responsibility of PM/GA with Marcela David de Carvalho)

In addition to water resources management, we promote information campaigns on aspects that may interfere with water quality and energy generation, such as golden mussels, cyanobacteria, aquatic macrophytes, reservoir siltation, iron-bacteria, among others.

In all our plants, we also carry out the control of inorganic and organic effluents and the drinking water used by employees. We currently have a Water Quality Management Center – NGQA, which has worked to make the monitoring suitable and uniform, so that the data obtained can be used by the Company itself in all its units and also by our partners, with the purpose of making a spatial and temporal assessment of the water in the reservoirs.

Sedimentary Monitoring

We operate fluviosedimentometric stations with the purpose of monitoring the intake and deposition of sediments in the reservoirs, aiming at:

  • Quantify and characterize sediments brought by rivers in some places of interest;
  • Estimate useful life of existing reservoirs and future developments;
  • Meet the environmental requirements for the release of Operating License – OL;
  • Alert the competent bodies about the degradation of the river basin;
  • Subsidize the actions of the Hydrographic Basin Committees and simultaneously comply with ANA/ANEEL Joint Resolution No. 3, from August 10, 2010.

This monitoring currently has stations located in different river basins, which operate in a detailed regime from where solid discharge measurements are often performed, by means of sampling techniques that allow, through their analysis, the calculation of the transported volume.

This sediment monitoring is currently carried out in 86 stations located in the vicinity of each of our Hydroelectric Power Plants (HPPs) and Small Hydroelectric Plants (SHPs).

Hydrometeorological Monitoring

We have started the operation of the hydro-meteorological network with the purpose of assessing the hydroelectric potential of Minas Gerais. Due to the growing development of the electrical sector, it was necessary to guarantee the operation of the network to ensure the generation of reliable hydrologic series, improving the planning of the expansion of the sector, in addition to ensuring steady energy.  

Currently, Cemig operates a hydro-meteorological network with 583 monitoring points, of which 232 are rainfall, 224 are waterways, 74 are reservoir and river levels, and 53 are weather stations, which monitor rainfall, temperature, air humidity, wind speed and direction, solar radiation and atmospheric pressure. These stations are distributed in strategic locations in the states of Minas Gerais, Goiás, Rio de Janeiro, Espírito Santo and Santa Catarina, and their data is received in real time at the Company’s headquarters in Belo Horizonte.

SISÁGUA” (responsibility of PM/GA with Marcela David de Carvalho)

Cemig Reservoirs Water Quality Information System (“Siságua”) is composed of a database of related data, which is generated from the water quality monitoring of our reservoirs and watercourses.

Considered an important tool for water quality management, “Sisagua” has a historical series in an interrelated database which allows data acquisition, storage, manipulation, integration and exposure, as well as ensuring the maintenance of all ecosystems involved (terrestrial, aquatic and interfaces).

The stored data is used in all our units and by our partners, for the interpretation of events, supporting new actions that reflect on continuous improvements in water quality and the control and management of aquatic fauna.