Tucurui Reservoir Experience and Lessons Learned Brief José Galizia Tundisi*, Instituto Internacional de Ecologia, Sao Carlos, Brazil, [email protected] Marco Aurélio Santos, Cidade Universitaria, Rio de Janeiro, Brazil Carlos Frederico S. Menezes, Electrobras, Rio de Janeiro, Brazil * Corresponding author 1. Introduction 2. Main Problems of Reservoirs in Brazil In the last 50 years, extensive construction of reservoirs 2.1 General Issues in many countries and watersheds in Latin America and particularly in Brazil, has produced a great number of artifi cial The general ecological consequences of river impoundments systems, which have interfered with the hydrology and ecology are related to several factors, among which the most important of several basins, sub-basins, and large rivers. Most of the are size, reservoir, volume, residence time of the water, and reservoirs were built up initially for power generation but lately geographic location. Many papers published in the international they have been used for multiple activities, such as irrigation, literature have reviewed and discussed their effects: inundation recreation, navigation, fi sheries and/or aquaculture. In Brazil, of valuable agricultural land; impairment of fi sh migration; loss there has been large-scale construction of reservoirs for the of terrestrial vegetation and fauna; changes in the river fauna purpose of hydroelectricity production, as shown in Table 1. and vegetation; hydrological changes downstream; interference in sediment transport regimes; the spreading of waterborne At present, approximately 30% of the hydroelectric potential diseases by producing a favorable environment for vectors; the of Brazil is being exploited. Several large-scale hydropower loss of cultural/historical heritages; social effects on the local projects are concentrated in the southeastern rivers, specifi cally populations including relocation; and changes in economic in the watersheds of the Tietê-Rio Grande, Paranapanema, and activities and traditional land uses and practices. Geophysical Paraná rivers, all of them sub-basins of the La Plata Basin problems due to water accumulation have also been pointed (3,000,000 km2). The production of hydroelectricity in Brazil out and several downstream changes reported (Ackerman et is strategic for the country’s development since approximately al. 1973; Balon and Coche 1974; J. Van der Heide 1982; Barrow 70% of the country’s energy is generated by large hydropower 1982 and 1987; Tundisi et al. 1993). All these consequences are reservoirs. One of the problems, however, is that most of the due to direct or indirect impacts. hydroelectric potential is concentrated in the north, far away from the large urban centers and industrialized regions, The multiple uses of reservoirs combined with biogeophysical demanding extensive transmission lines. These new reservoirs and social characteristics produce many complexities, cause impacts on regional and local ecosystems and in the economic and hydro-social cycles. Table 1. Generation of Energy in Brazil. Power Reservoirs in Brazil, therefore, provide a reference point in Type Number % (MW) river systems since their evolution, changes in water quality and eutrophication, and alterations in fl ora and fauna refl ect Hydropower plant 138 64,197.6 70.91 existing watershed management, policies and the use of Small hydropower 208 896.7 0.99 the land system (Straskraba, Tundisi and Duncan 1993). As projects intermediate systems between rivers and lakes, reservoirs Central hydroelectric 144 78.4 0.09 have many mechanisms of functioning and the process of generator following up their changes is a theoretical and practical study Thermoelectric plant 654 13,113.2 14.48 of high signifi cance. The main uses of reservoirs in Brazil are: Thermonuclear plant 2 2,007 2.22 • Hydroelectricity; Central wind generator 9 22 0.02 • Water storage for irrigation; Subtotal 1,155 80,314.9 88.70 • Water storage for drinking purposes; Importation 8 8,170 9.02 • Production of biomass (fi sheries and aquaculture); • Transportation and long distance navigation; Emergency generation 54 2,049.5 2.26 • Recreation and tourism; and, Total 1,217 90,534.4 100 • Water storage for cooling purposes (industry). Source: ANEEL (2003). confl icts, and diffi culties demanding innovative procedures, • Energy production; new approaches and innovative solutions for adequate • Control of transport of suspended material; management. In addition several of these artifi cial systems are • Sources of water supply; spatially complex, have a dendritic pattern, many side arms, • New opportunities for recreation and tourism; and narrow channels near the tributaries. • Enhanced aquaculture; • Navigation; In general the reservoirs in Brazil, besides the problems • Increased potential of water for irrigation; addressed above, produced, after fi lling, serious impacts due • Flood control and river regulation; to water quality deterioration as a consequence of watershed • Fishery increased and aquaculture; uses, as well as, discharge of industrial effl uents, residues of • Low-energy water purifi ers; and, agricultural uses, and untreated sewage disposal. Populations • New economic alternatives in regional systems. living along the river have had to adapt to the new hydro- social cycle created as a result of reservoir construction and The time of stabilization of the new hydro-socio-economic- operation. The main problems of reservoirs in Brazil are: water quality-limnological system varies from region to region, with watershed uses and with the degree of urbanization • Eutrophication; and economic development, as well as with the general • Increased toxicity and general contamination; characteristics of the reservoir and its construction. • Siltation and rapid fi lling-up with sediment; • Spreading of waterborne diseases; 2.2 Amazonian Reservoirs • Salinization (in reservoirs in northeast Brazil); • Anoxic hypolimnion and severe downstream impacts The Amazon Basin with 6,000,000 km2 of drainage area (mainly in Amazonian reservoirs); has a tropical warm climate and a discharge of 3,767.8 km3 • Low diversity of fi sh fauna as compared to rivers; a year. The average humidity is 80%. One of the important • High internal load and toxic sediment; characteristics of this region is the high water-level fl uctuation • Extensive macrophyte growth associated with eutrophication; between the rainy and dry seasons promoting a corresponding • Loss of arable land; and, hydro-social cycle (fi sheries, fl oodplain exploitation, local • Relocation of population. navigation) (Tundisi 1994 and 2003; Junk et al. 1987). Despite these impacts, reservoir construction in Brazil has In the Brazilian Amazonian region there are 5 reservoirs in produced many positive results related to the national operation: Couracy Nunes, Curua Una, Tucurui, Balbina, economy (hydroelectricity production) and regional and Samuel. Table 2 gives information on the technical development by stimulating new alternatives for economic characteristics of these Amazonian reservoirs. These and social exploitation of the water-impounded resources. The Amazon reservoirs produce several alterations in the aquatic positive achievements of reservoir construction in Brazil are: environment, related to the high amount of organic matter Table 2. Characteristics of the Five Amazonian Reservoirs. Reservoir Technical Characteristics Coaracy Nunes Curuá-Una Tucuruí Balbina Samuel Location (State) Amapá Pará Pará Amazonas Rondônia Main river Araguari Curuá-Una Tocantins Uatumã Jamari Drainage area (km2) 25,000 15,300 803,250 18,450 15,280 Filling phase (month) - - 6 18 5 Operation Nov/75 1976 Mar/85 Feb/89 Jul/89 Power plant (MW) 40 40 4,000 250 216 Retention time (month) - 1 1.7 11.7 3.5 Operational depth (m) 120 68 72 50 87 Inundated area (km2)23782,875 2,360 560 Total volume (km3) 0.138 0.472 45.5 17.5 3.2 Average discharge (m3/s) 1,045 - 11,000 577 350 Maximum length (km) - 56 170 210 140 Maximum width (km) - 4 40 75 20 Maximum depth (m) - 18 75 30 - Average depth (m) - 5 19 11 - Source: ELECTROBRAS/DNAEE (1997). 422 Tucurui Reservoir accumulated due to the inundation of tropical rain forest, new covered with tropical rainforest, situated in the area of the physicochemical gradients in the water column (related to Tucurui reservoir project. Table 3 gives the average monthly thermal stratifi cation, conductivity, dissolved oxygen, and pH), fl ows of the Tocantins River at the town of Tucurui. excessive growth of macrophytes, and insect proliferation. Downstream, the main negative impacts are related to changes 3.2 Biogeophysical Features of the Reservoir and Its in the hydrological cycle interfering with the fl ood pulse of the Basin fl oodplains, and alterations in the water chemistry. Tucurui Reservoir has a surface area of approximately 2,430 3. The Tucurui Hydroelectric Plant and Its km2, with a storage capacity of 45 km3. The reservoir has a Reservoir complex dendritic pattern and has inundated a vast area of tropical rainforest, most of which was not removed during 3.1 General Background: The Tucurui Reservoir Basin the fi lling phase. A power construction plant was initiated in 1975, and operation started in 1984 with an installed capacity The watershed of the Araguaia and Tocantins rivers (Figure 1), 7XFXUXL 2 78&858,5(6(592,5%$6,1 has an area of 803,250 km %5$=,/ (IBGE 1991) and an average 'UDLQDJH%DVLQ%RXQGDU\ 7XFXUXL 3 6WDWH%RXQGDU\ 5HVHUYRLU discharge of 11,000 m /s. The 5LYHU -DFXQGD 0$5$1+$2 Tocantins River has an length /DNH of 2,500 km and the Araguaia 6HOHFWHG&LW\ ,PSHUDWUL] is a fl oodplain river 2,115 km 7 0DUDED R F 5 D QD LX Q long. The area of the Tocantins D W F L D 5 Q W , V V NP D River is shared by the states of E 5 H S X /RQWUD5 Tocantins (58%), Mato Grosso D HUPHOKR5 U 9 $UDJXDLD5 D 3 ) (24%), Pará (13%), Maranhão DULQKD5 $UJXDLQD (4%), and the Federal District &DUROLQD 1 )LODGHOILD 0DQXHO (1%). A large basin is formed 3 $5$ 3DX $OYHV G $UFR5 *UDQGHV5 by the Araguaia-Tocantins 0DQXHO $UURLRVGR $OYHV Rivers, and several tributaries $UDJXDLD5 &RQFHLFDR 3HTXHQR5 GR$UDJXDLD of regional importance.