SOBRADINHO RESERVOIR

A westward view from the damside hill-top

Photo.
Photo: A.Kurata


A. LOCATION


B. DESCRIPTION

    This is the largest reservoir in Brazil in terms of surface area, situated in the north of the State of Bahia. The dam was built in the hydrologic basin of the River Sao Francisco at a distance of 748 km from its source and 1,912 km from its estuary on the Atlantic coast. The power generation was started on 31 November 1979.
    It covers an area of 4,225 km2 with mean depth of 8.6 m and a maximum depth of 30 m. At the maximum elevation of 392.5 m above sea level, the reservoir accumulates 34.1x1.0E+9 m3 of water with a regulated discharge rate of 1,060 m3 sec 1.
    The geological formation of the region consists of very ancient rocks of the Brazilian shield, igneous or highly metamorphosed and dating back to the Precambrian era. The soils are predominantly latosol, quartz sand and lithosol. The climate is semi-arid, characterized by very high evaporation rate. Mean annual rainfall ranges between 400 mm and 800 mm and mean annual temperature of 26 27deg C is affected by the water body of the reservoir. The prevailing vegetation consists of caranauba (a type of palm tree), hypoxerophilous and hyperxerophilous shrubs of medium height, and low shrubs. When the water level becomes low, wet areas around the reservoir are cultivated (Q).

C. PHYSICAL DIMENSIONS (Q)

    Surface area [km2] 4,220
    Volume [km3] 34.1
    Maximum depth [m] 30
    Mean depth [m] 8.6
    Water level Regulated
    Normal range of annual water level fluctuation [m] 4.5
    Length of shoreline [km] 1,690
    Residence time [yr] 0.35
    Catchment area [km2] 498,425

D. PHYSIOGRAPHIC FEATURES (Q)

D1 GEOGRAPHICAL

    Fig. SAM-10-1
    Sketch map of the reservoir.

D2 CLIMATIC
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    Mean temp. [deg C] 23.1 27.3 26.6 26.5 25.8 24.7 24.4 25.0 26.9 28.0 28.2 27.6 26.0
    Precipitation [mm] 60 101 122 58 13 9 5 1 3 11 51 88 522
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    2 - - - - - - - - 25.1 - 32.3 27.2
    4 - - - - - - - 22.8 23.0 25.6 - 26.3
    6 - - - - - - - 24.9 - 26.4 27.1 27.0
    7 - - - - - - - 25.5 24.1 - 26.5 27.7
    7.5 - - - - - - - 27.4 27.2 - 28.4 29.0
    8 - - - - - - - 25.5 26.6 - 27.4 28.1
    15 - - - - - - - 24.4 - 25.9 25.9 27.0

E. LAKE WATER QUALITY (Q)

E1 TRANSPARENCY
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    - - - - - - - - 2.50 2.50 2.20 - 1.00
E2 pH
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    2 - - - - - - - - 8.2 - 8.3 8.5
    4 - - - - - - - 7.0 7.5 8.0 8.0 -
    6 - - - - - - - 7.2 - 7.0 7.6 7.0
    7 - - - - - - - 8.0 6.9 - 7.6 7.5
    7.5 - - - - - - - 7.6 6.5 - 7.5 7.4
    8 - - - - - - - 7.5 7.1 - 7.7 7.7
    15 - - - - - - - 7.6 - 7.7 7.8 7.2
E4 DO [mg l-1]
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    2 - - - - - - - - 7.4 - 6.8 5.1
    4 - - - - - - - 6.7 7.3 7.5 - 5.3
    6 - - - - - - - 6.3 - 8.5 5.3 5.5
    7 - - - - - - - 7.4 8.4 - 7.5 5.0
    7.5 - - - - - - - 7.2 7.3 - 6.9 4.4
    8 - - - - - - - 7.4 7.3 - 6.4 4.5
    15 - - - - - - - 7.8 - 8.3 5.2 4.8
E7 NITROGEN CONCENTRATION
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    4 - - - - - - - 0.02 0.03 1.01 - 3.52
    6 - - - - - - - 0.04 - 0.35 0.39 1.76
    7.5 - - - - - - - 0.04 3.96 - 0.53 5.28
    8 - - - - - - - 1.32 3.96 - 3.96 7.92
    15 - - - - - - - 0.40 - 1.76 0.59 1.32
E8 PHOSPHORUS CONCENTRATION
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    2 - - - - - - - - - - 0.00 0.00
    4 - - - - - - - - - 0.02 - 0.01
    6 - - - - - - - - - 0.00 0.01 0.00
    7 - - - - - - - - 0.01 - 0.01 0.01
    7.5 - - - - - - - - 0.01 - 0.00 0.10
    8 - - - - - - - - 0.01 - 0.01 0.01
    15 - - - - - - - - - 0.02 0.02 0.40
E9 CHLORIDE CONCENTRATION [mg l-1]
    Near the dam, 1981 1982
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    2 - - - - - - - - 10.0 - 10.0 8.0
    4 - - - - - - - 1.0 1.0 2.0 - 6.0
    6 - - - - - - - 1.0 - 2.0 3.0 6.0
    7 - - - - - - - 1.3 1.0 - 3.0 53.0
    7.5 - - - - - - - 4.0 4.0 - 3.0 8.0
    8 - - - - - - - 17.0 4.0 - 36.0 53.0
    15 - - - - - - - 3.0 - 5.0 2.0 5.0

F. BIOLOGICAL FEATURES (Q)

    1981 1982
F1 FLORA F2 FAUNA F5 FISHERY PRODUCTS

G. SOCIO-ECONOMIC CONDITIONS (Q)

G1 LAND USE IN THE CATCHMENT AREA
    1988
    Area [km2]
    Agricultural land 168.1
G3 POPULATION IN THE CATCHMENT AREA
    1980
    Population Population density [km 2] Major cities
    Urban 35,686 - Bossoroca, Remanso, Sento Se
    Rural 78,310 - Pilao Aracado, Ibiraba, Barra
    Total 113,996 0.23

H. LAKE UTILIZATION (Q)

H1 LAKE UTILIZATION
    Navigation and transportation (36,037 metric tons of cargo in 1990), irrigation, sightseeing and tourism (3,000 tourists in 1990), fisheries and power generation.

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I2 TOXIC CONTAMINATION I4 ACIDIFICATION I5 OTHER HAZARDS
    Utilization of inlet areas for agriculture during the period of the low water level.

J. WASTEWATER TREATMENTS (Q)

J3 SANITARY FACILITIES AND SEWERAGE

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS

(Q) M1 NATIONAL AND LOCAL LAWS CONCERNED M2 INSTITUTIONAL MEASURES
  1. Centro de Pesquisas e Desenvolvimento da Bahia (CEPED), during 1982 1986
  2. Secretaria de Planejamento de Ciencia e Tecnologia de Bahia
  3. Empresa de Assistencia Tecnica e Extensao Rural da Bahia (EMATERBA)
M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES
  1. Centro de Recursos Ambientais da Bahia (CRA)
  2. Instituto Brasileiro de Meio Ambiente e Recursos Naturais Renovaveis (IBAMA)
  3. Centro de Pesquisas e Desenvolvimento de Bahia (CEPED)

N. SOURCES OF DATA

  1. Questionnaire filled by CHESF (Hydroelectric Company of the Sao Francisco River) and from the following persons and sources. English version rendered by Prof. Vajapeyam S. Srinivasan, Dept. of Civil Engineering/CCT, Federal University of Paraiba, Campus II, Campina Grande, PB.
  2. Alexandar Max Figueiredo de Sa, Division for Studies, Control and Operation with Hydrometeorological Data (DOCH).
  3. Andre de Barros Correia, Department of Environment (DMA).
  4. Jose Severino de Oliveira, Department of Environment (DMA).
  5. Paredes, J. F., Rocha, W. L., Caim, A. J. & Doria, E. M. da C. (1983) Sao Francisco River at the Hydrological Studies.
  6. Vianna, Marcelo D.B. (1976) Analise do Impacto Ambiental. Documento da Construcao do Reservatorio de Sobradinho. Aspectos Referentes as Modificacoes Ecologica.
  7. Secretaria do Planejamento e Tecnologia, CEPED (CRA, EMATERBA e SUDENE) Anais sobre Acompanhamento Evolutivo do Cabo de Sobradino.
  8. Gooldland, R. (1974) Reconhecimento do Impacto Ambiental para o Projeto Sobradinho.
  9. Imagens Sensoriamento Remoto S/C Ltda. (1990) Mapeamento e Analise Temporal do Uso da Terra no Entorno do Reservatorio de Sobradinho.
  10. PROTAM (1982 1986) Programa de Tecnologia Ambiental. Diagnosticos do Acompanhamento Evolutivo das Pescas no Reservatorio de Sobradinho.
  11. Ratisbona, L. R. (1976) The Climate of Brazil "World Survey of Climatology, Volume 12, Climates of Central and South America" (ed. Schwerdtfeger, W.), P. 289, Elsevier Scientific Publishing Company, Amsterdam-Oxford-New York.