BRAZILIAN ELECTRICITY REGULATORY AGENCY - ANEEL Hydrological Studies and Information Department - SIH RESERVOIR SEDIMENTATION

ASSESSMENT GUIDELINE

Newton de Oliveira Carvalho

Civil Engineer ?DSC

Consultor in Hydrossedimentology

Rio de Janeiro, RJ - Brazil

Naziano Pantoja Filizola J鷑ior

Geologist ?Master Sci. and Doctor

Federal University of Amazonas

Manaus, AM - Brazil

Paulo Marcos Coutinho dos Santos

Geologist

ANA ?National Agency for Water

Brasia, DF - Brazil

Jorge Enoch Furquim Werneck Lima

Agronomic Engineer ?Master Sci. and Doctor

EMBRAPA ?CERRADOS

Brasia, DF - Brazil

Brasilia, DF ?2000

- Revision of English version - 2014 ?/P>

Original presentation in the portuguese version

RESERVOIR SEDIMENTATION

ASSESSMENT GUIDELINE

SUMMARY 1.        Introduction.................................................................................................. 5

2.        Reservoirs with sedimentation problems in Brazil......................................   7

3.        Deposition of sediments in reservoirs?...................  9

4.        The relevance of the sedimentation assessment survey for hydropower

plants ........................11

       4.1 Inventory stage........12

       4.2 Feasibility and basic project stages .12

       4.3 Operational stage ..................................................13

5.        Factors affecting sediments yield  ........................................14

6. Reservoir sedimentation assessment .................................................15

6.1 Reservoir data ...........................................................................15

7. Sediment production determination....................................................17

       7.1 Erosion assessment............................................................................18

       7.2 Sedimentometric gaging stations networking........................18

       7.3 Gaging station installation and measurement frequency ..............  19

       7.4 Measurement methods.........................................................................    20

              7.4.1 Sediment sampling..................................................   27

7.4.2 Laboratory analysis......................................................... 29

7.4.3 Sediment discharge computation............................................    31

       7.5 Data processing .....................................................................  34

              7.5.1 Continuous, hourly and daily measurements.....................       35

              7.5.2 Eventual measurements............................................. 36

              7.5.3 Data regionalization.....................................................  40

8. Reservoirs Trapping Efficiency .....................................    42

       8.1 Medium and large reservoirs cases ?using Brune curve . 42

       8.2 Small reservoirs case ?using Churchill curve .. 43

9. Specific weight of deposits.............................................厖厖厖厖...     46

       9.1 Computed ............................................................................................   46

       9.2 Measured ..............................................................................................  48

       9.3 Estimate ..............................................................................................    48

10. Evaluation of a reservoir sedimentation ..........................................................     50

       10.1 Sedimentation assessment methods 厖............................................  50

10.2 Assessment of total sedimentation, and dead storage 厖?....... 51

10.3 Assessment of reservoir useful life ?..............................................      52

10.4 Sediments distribution in reservoirs..................................................       52

       10.5 Increase on basin erosion ?.?.........................................................  53

11. Measurement of reservoirs sedimentation...............................厖厖..........    56

       11.1 Purpose of the survey..........................................................................  56

       11.2 Frequency of surveys..........................................................................   57

       11.3 Survey methods...................................................................................  58

              11.3.1 Contour survey 厖厖厖.................................?.......      58

              11.3.2 Topo-bathymetric survey .....................................................       58

       11.4 Survey specifications...........................................................................  65

       11.5 Bed mapping ....................................................?............厖?.....  68

       11.6 Computation of reservoir volumes......................................................   62

       11.7 Computation of settled sediments volume ..........................厖厖 71

11.8 Outline of new level x area x volume curves.................?............. 72

       11.9 New geometry of the lake and pivot point 厖厖厖?.........     71

       11.10 Bed scanning and geophysics厖...................................................   73

12. Control of a reservoir sedimentation.................................................................    74

       12.1 Preventive control................................................................................  74

       12.2 Corrective practices ............................................................?............ 75

              12.2.1 Dredge of sediments 厖厖?......................厖厖 76

13 Secondary effects due to sediments..........................................................?..      78

13.1 Effects on the reservoir backwater ....................................................     78

13.2 Changes on water quality.....................................................................    79

       13.3 Ecological effects ...............................................................................  79

       13.4 Erosion on reservoirs banks...................?.........................?...........  80

       13.5 Deposit erosion......................................................................................80

       13.6 Downstream effects...................................厖厖..............?........ 80

              13.6.1 Channel degradation ....................................................?....      81

              13.6.2 Dominant discharge .................................厖....................       83          13.6.3 Channel hydraulic features?...............................厖?      83          13.6.4 Method of degradation limited by armoring ?...厖?      83          13.6.5 Method of degradation constrained by stable slope....厖.       88

       13.7 Reservoir surveys supported by satellite imagery..............?.............  91

13.8 Erosion control at the downstream channel...................厖?........     92

Bibliography (consulted and complementary) ........................................................    93

Glossary of terms, symbols and units ...........................................厖..................   100