Possible options to slow down the advancement rate of Tarbela delta

Habib-ur-Rehman, _; Rehman, Mirza Abdul; Naeem, Usman; Hashmi, Hashim Nisar; Shakir, Abdul Sattar

doi:10.1007/s10661-017-6376-6

Cited by 10 publications

(11 citation statements)

References 6 publications

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“…As the future pool levels are not known at the dam, various scenarios have to be developed and simulated to establish the uncertainties inherent in predictions of future trends. It is surmised that the future reservoir operation levels have a greater impact on reservoir sedimentation than the water inflow time series [14,15].…”

Section: Reservoir Operational Levelsmentioning

confidence: 99%

“…The curves depict a linear behavior, which indicates the filling of reservoir and fall and corresponds to maximum outflows, respectively. This approach is followed in engineering studies that treat reservoir sedimentation [14,15,43]. Generalized reservoir-operating rule curves have been proposed to analyze the reservoir operational impact on reservoir sedimentation and its movement (Figure 8).…”

Section: Reservoir Operational Levelsmentioning

confidence: 99%

“…Most of the incoming sediments are deposited in a reservoir during such events if a high reservoir level is maintained. On the other hand, if the reservoir water level has been kept low, a large quantity of incoming sediments travels through the reservoir and often leads to degradation of already deposited sediments [14,15]. [14] and Petkovsek (2014) [15] estimated that sediment delta advancement is reduced by increasing the minimum reservoir operating level, but it also decreases the storage volume of the reservoir and vice versa.…”

Section: Introductionmentioning

confidence: 99%

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Simulating the Impact of Climate Change with Different Reservoir Operating Strategies on Sedimentation of the Mangla Reservoir, Northern Pakistan

Khan

Stamm

Haider

2020

Water

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Reservoir sedimentation reduces the gross storage capacity of dams and also negatively impacts turbine functioning, posing a danger to turbine inlets. When the sediment delta approaches the dam, further concerns arise regarding sediments passing through turbine intakes, blades abrasion due to increased silt/sand concentration, choking of outlets, and dam safety. Thus, slowing down the delta advance rate is a worthy goal from a dam manager’s viewpoint. These problems can be solved through a flexible reservoir operation strategy that prioritize sediment deposition further away from the dam face. As a case study, the Mangla Reservoir in Pakistan is selected to elaborate the operational strategy. The methodology rests upon usage of a 1D sediment transport model to quantify the impact of different reservoir operating strategies on sedimentation. Further, in order to assess the long-term effect of a changing climate, a global climate model under representative concentration pathways scenarios 4.5 and 8.5 for the 21st century is used. The reduction of uncertainty in the suspended sediments concentration is achieved by employing an artificial neural networking technique. Moreover, a sensitivity analysis focused on estimating the impact of various parameters on sediment transport modelling was conducted. The results show that a gradual increase in the reservoir minimum operating level slows down the delta movement rate and the bed level close to the dam. However, it may compromise the downstream irrigation demand during periods of high water demand. The findings may help the reservoir managers to improve the reservoir operation rules and ultimately support the objective of a sustainable reservoir use for the societal benefit.

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Section: Reservoir Operational Levelsmentioning

confidence: 99%

Section: Reservoir Operational Levelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulating the Impact of Climate Change with Different Reservoir Operating Strategies on Sedimentation of the Mangla Reservoir, Northern Pakistan

Khan

Stamm

Haider

2020

Water

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“…The observed standard deviation was at 0.041. In a recent study [46], the HEC-RAS model was validated for the Tarbela Reservoir by simulating it only for one year, and an approximately 20-m difference between the observed and simulated river beds for the sediment delta in the year 2000 was found. However, in the present study, the difference of four years of simulation was only 4-5 m in the whole longitudinal profile (Figure 9).…”

Section: Model Validationmentioning

confidence: 99%

“…However, in the present study, the difference of four years of simulation was only 4-5 m in the whole longitudinal profile (Figure 9). A better modeling performance might be due to more accurate sediment load boundary conditions generated using a long-term data series, i.e., 1969-2014, whereas [46] used only a 28-year data series, i.e., 1979-2006. To validate the HEC-RAS model with the above calibrated WA-ANN sediment series, it was run for another four years up to 2017, similar to the SRC model. The output was compared with observed sediment deposits of 2017 and presented in Figure 10.…”

Section: Model Validationmentioning

confidence: 99%

Effect of Sediment Load Boundary Conditions in Predicting Sediment Delta of Tarbela Reservoir in Pakistan

Tarar

Ahmad

et al. 2019

Water

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Setting precise sediment load boundary conditions plays a central role in robust modeling of sedimentation in reservoirs. In the presented study, we modeled sediment transport in Tarbela Reservoir using sediment rating curves (SRC) and wavelet artificial neural networks (WA-ANNs) for setting sediment load boundary conditions in the HEC-RAS 1D numerical model. The reconstruction performance of SRC for finding the missing sediment sampling data was at R2 = 0.655 and NSE = 0.635. The same performance using WA-ANNs was at R2 = 0.771 and NSE = 0.771. As the WA-ANNs have better ability to model non-linear sediment transport behavior in the Upper Indus River, the reconstructed missing suspended sediment load data were more accurate. Therefore, using more accurately-reconstructed sediment load boundary conditions in HEC-RAS, the model was better morphodynamically calibrated with R2 = 0.980 and NSE = 0.979. Using SRC-based sediment load boundary conditions, the HEC-RAS model was calibrated with R2 = 0.959 and NSE = 0.943. Both models validated the delta movement in the Tarbela Reservoir with R2 = 0.968, NSE = 0.959 and R2 = 0.950, NSE = 0.893 using WA-ANN and SRC estimates, respectively. Unlike SRC, WA-ANN-based boundary conditions provided stable simulations in HEC-RAS. In addition, WA-ANN-predicted sediment load also suggested a decrease in supply of sediment significantly to the Tarbela Reservoir in the future due to intra-annual shifting of flows from summer to pre- and post-winter. Therefore, our future predictions also suggested the stability of the sediment delta. As the WA-ANN-based sediment load boundary conditions precisely represented the physics of sediment transport, the modeling concept could very likely be used to study bed level changes in reservoirs/rivers elsewhere in the world.

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Performance evaluation of 1-D numerical model HEC-RAS towards modeling sediment depositions and sediment flushing operations for the reservoirs

Habib-ur-Rehman

Chaudhry²,

Naeem

et al. 2018

Environ Monit Assess

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Sediment inflow to the reservoir is a key factor to calculate life of the reservoir. Flushing is a very useful technique in order to enhance the life of reservoir. From the literature review, 14 reservoirs were considered where flushing has already been practiced and only 6 reservoirs were found successful in flushing. The others were found partially flushed. In this research, data of three successfully flushed reservoirs namely Baira reservoir (India), Gebidem reservoir (Switzerland), and Gmund reservoir (Austria) were used to run 1-D numerical model HEC-RAS. In the first phase, the longitudinal profiles of delta were modeled and calibrated with observed sediment depositions. In the presence of available data of discharges and respective reservoir levels, the modeled deltas were used for flushing the deltas. With the help of modeled delta and corresponding flushing discharges, sediment deposition and flushing durations were computed. The simulated flushed durations were 31, 102, and 180 h for Baira, Gebidem, and Gmund reservoirs, respectively. The simulated flushed durations were found close to observed durations. Hence, the use of 1-D numerical model HEC-RAS is encouraged for modeling of sediment deposits and flushing operations.

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Possible options to slow down the advancement rate of Tarbela delta

Cited by 10 publications

References 6 publications

Simulating the Impact of Climate Change with Different Reservoir Operating Strategies on Sedimentation of the Mangla Reservoir, Northern Pakistan

Simulating the Impact of Climate Change with Different Reservoir Operating Strategies on Sedimentation of the Mangla Reservoir, Northern Pakistan

Effect of Sediment Load Boundary Conditions in Predicting Sediment Delta of Tarbela Reservoir in Pakistan

Performance evaluation of 1-D numerical model HEC-RAS towards modeling sediment depositions and sediment flushing operations for the reservoirs

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