Reservoir Sedimentation Assessment Guideline (Carvalho et al., 2014)
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 Júnior
Geologist – Master Sci. and Doctor
Federal University of Amazonas
Manaus, AM - Brazil
Paulo Marcos Coutinho dos Santos
Geologist
ANA – National Agency for Water
Brasília, DF - Brazil
Jorge Enoch Furquim Werneck Lima
Agronomic Engineer – Master Sci. and Doctor
EMBRAPA – CERRADOS
Brasília, DF - Brazil
Brasilia, DF – 2000
- Revision of English version - 2014 –
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.............................................……………………... 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 ……............................................ 50
10.2 Assessment of total sedimentation, and dead storage ………........ 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...............................………….......... 56
11.1 Purpose of the survey.......................................................................... 56
11.2 Frequency of surveys.......................................................................... 57
11.3 Survey methods................................................................................... 58
11.3.1 Contour survey ……………….................................…........ 58
11.3.2 Topo-bathymetric survey ..................................................... 58
11.4 Survey specifications........................................................................... 65
11.5 Bed mapping ....................................................….............………...... 68
11.6 Computation of reservoir volumes...................................................... 62
11.7 Computation of settled sediments volume ..........................………… 71
11.8 Outline of new level x area x volume curves.................….............. 72
11.9 New geometry of the lake and pivot point ………………….......... 71
11.10 Bed scanning and geophysics……................................................... 73
12. Control of a reservoir sedimentation................................................................. 74
12.1 Preventive control................................................................................ 74
12.2 Corrective practices ............................................................…............. 75
12.2.1 Dredge of sediments …………….......................………… 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...................................…………..............…......... 80
13.6.1 Channel degradation ....................................................…..... 81
13.6.2 Dominant discharge .................................…….................... 83 13.6.3 Channel hydraulic features…................................………. 83 13.6.4 Method of degradation limited by armoring … ...………. 83 13.6.5 Method of degradation constrained by stable slope....……. 88
13.7 Reservoir surveys supported by satellite imagery..............….............. 91
13.8 Erosion control at the downstream channel...................………......... 92
Bibliography (consulted and complementary) ........................................................ 93
Glossary of terms, symbols and units ...........................................…….................. 100