11 research outputs found

    Simulation-optimization of Tarbela Reservoir operation to enhance multiple benefits and to achieve sustainable development goals

    Get PDF
    Pakistan’s agriculture and economy rely heavily on the Tarbela Reservoir. The present storage capacity of Tarbela is 8.2 BCM and it has been depleted by more than 40% due to sedimentation since 1976. It also has had a 0.94 percent (0.134 BCM) decrease in gross reservoir capacity every year. Historically, the amount of sediment trapped in the Tarbela Reservoir during the period 1976–2020 was 198.5 million tonnes annually. Based on the current operation by the Water and Power Development Authority (WAPDA), the delta is expected to extend to 2.41 km from the dam in 2035. The reservoir will become a run-of-the-river reservoir with a gross storage capacity of 2.87 BCM. This rapid loss of storage capacity will significantly impact reservoir benefits while also putting turbine performance at risk due to abrasion. Slowing the sediment deposition phenomena by a flexible operational strategy is a worthwhile aim from the dam manager’s viewpoint to achieve Sustainable Development Goals (i.e., poverty and hunger alleviation, clean affordable energy, protecting ecosystem etc.). Therefore, for the safe and long-term operation of the turbines, the existing Standard Operating Procedures (SOPs) adopted by WAPDA need to be appraised to delineate their impact on future optimized operations. The aspect of considering static SOPs on the whole period of reservoir operation has not been attempted earlier. The Tarbela Reservoir was selected as a case study to enhance the existing reservoir operation. The methodology relies upon the use of a 1-D sediment transport model in HEC-RAS to study the impact of the operational strategy on sedimentation. In conjunction, the existing reservoir operation of Tarbela was modelled in HEC-ResSim using its physical, operational, and 10-daily time-series data for simulation of releases and hydropower benefits based on a revised elevation-capacity curve for sedimentation. After calibration and validation, the model was applied to predict future reservoir operation impacts on a 5-year basis from 2025 to 2035 for determining storage capacity, irrigation releases, power production and energy generation. It was predicted that as the storage capacity of the reservoir is depleted (by application of the WAPDA current SOPs in future years), the irrigation releases would be increased in the Kharif season (April–September) by 7% and decreased by 50% in the Rabi season (October–March) with a corresponding increase in power generation by 4% and decrease by 37%, respectively, and the average annual energy generation would be decreased by 6.5%. The results showed that a gradual increase in the minimum operating level will slow down delta movement but it will reduce irrigation releases at times of high demand. The findings may assist water managers to improve the Tarbela Reservoir operation to achieve sustainable development goals and to attain societal future benefits

    Sustainable sediment management options for reservoirs: a case study of Chashma Reservoir in Pakistan

    No full text
    Abstract Globally the average annual loss of reservoir capacity is approximately 1%. Pakistan is confronting major issue of sedimentation which is continuously depleting the useful storage of reservoirs. GSTARS3 model was used to determine the rate of deposition and sediment pattern of Chashma Reservoir since its operation. The model was calibrated and validated for bathymetric survey of 2008 and 2012. The results of GSTARS3 were incorporated to a GIS software to visualize sediment accumulation in reservoir. The study reveals that sediment flushing of the Chashma Reservoir can be carried out during flood season at a pond level of 638.15 ft. (194.51 m). However, its negative impact if any on the hydropower generation needs to be analysed. Accordingly, modified operation rules would be required

    Flood inundation mapping for the Gwadar city

    No full text
    Floods wreak havoc with human society, infrastructure and the environment. Accuracy and reliability of the forecasts concerning the resultant inundation depths and extents of these floods are primarily dependent upon the employed hydrologic modeling approach. In the present study, a more precise distributed hydrological modeling approach has been exploited with grid-based spatial discretization for the simulation of flood inundation in Akara river watershed which contains a proposed metropolitan-level developed coastal city of Gwadar in the ‘Balochistan’ province of Pakistan. Institute of Industrial Sciences Distributed Hydrological Model, a physically based distributed hydrological model, has been employed. This model, through fully implicit finite difference schemes, utilizes diffusive wave approximations of 1D and 2D Saint Venant’s governing equations for the river and over-land flow components, respectively. While the model is calibrated against the cyclonic flood event of June 2007, to earmark the potential hazardous areas inside as well as outside the Master Plan boundary the flood inundation simulation for the worst precipitation events of 50 and 100 years return periods are performed. The simulated flood inundation depths at various known locations showed good agreement with the observed ones. Moreover, the simulations depict that the simulated flood inundation depths at the same locations increase by 1.07 to 1.87 times and 1.21 to 1.89 times respectively due to 50 and 100 years return period rainfalls

    Simulation-Optimization of Tarbela Reservoir Operation to Enhance Multiple Benefits and to Achieve Sustainable Development Goals

    No full text
    Pakistan’s agriculture and economy rely heavily on the Tarbela Reservoir. The present storage capacity of Tarbela is 8.2 BCM and it has been depleted by more than 40% due to sedimentation since 1976. It also has had a 0.94 percent (0.134 BCM) decrease in gross reservoir capacity every year. Historically, the amount of sediment trapped in the Tarbela Reservoir during the period 1976–2020 was 198.5 million tonnes annually. Based on the current operation by the Water and Power Development Authority (WAPDA), the delta is expected to extend to 2.41 km from the dam in 2035. The reservoir will become a run-of-the-river reservoir with a gross storage capacity of 2.87 BCM. This rapid loss of storage capacity will significantly impact reservoir benefits while also putting turbine performance at risk due to abrasion. Slowing the sediment deposition phenomena by a flexible operational strategy is a worthwhile aim from the dam manager’s viewpoint to achieve Sustainable Development Goals (i.e., poverty and hunger alleviation, clean affordable energy, protecting ecosystem etc.). Therefore, for the safe and long-term operation of the turbines, the existing Standard Operating Procedures (SOPs) adopted by WAPDA need to be appraised to delineate their impact on future optimized operations. The aspect of considering static SOPs on the whole period of reservoir operation has not been attempted earlier. The Tarbela Reservoir was selected as a case study to enhance the existing reservoir operation. The methodology relies upon the use of a 1-D sediment transport model in HEC-RAS to study the impact of the operational strategy on sedimentation. In conjunction, the existing reservoir operation of Tarbela was modelled in HEC-ResSim using its physical, operational, and 10-daily time-series data for simulation of releases and hydropower benefits based on a revised elevation-capacity curve for sedimentation. After calibration and validation, the model was applied to predict future reservoir operation impacts on a 5-year basis from 2025 to 2035 for determining storage capacity, irrigation releases, power production and energy generation. It was predicted that as the storage capacity of the reservoir is depleted (by application of the WAPDA current SOPs in future years), the irrigation releases would be increased in the Kharif season (April–September) by 7% and decreased by 50% in the Rabi season (October–March) with a corresponding increase in power generation by 4% and decrease by 37%, respectively, and the average annual energy generation would be decreased by 6.5%. The results showed that a gradual increase in the minimum operating level will slow down delta movement but it will reduce irrigation releases at times of high demand. The findings may assist water managers to improve the Tarbela Reservoir operation to achieve sustainable development goals and to attain societal future benefits

    River bank erosion and channel evolution in sand-bed braided reach of River Chenab: role of floods during different flow regimes

    No full text
    Braided reaches of large rivers in alluvial plains show major morphological changes, particularly the external bank erosion, due to the flood events. This paper highlights the bank erosion and channel evolution induced by eleven different flood events in a 7-km long reach of the River Chenab, Pakistan. The impact of floods on river bank erosion and channel evolution is analyzed under low and high flow conditions. Flood-induced changes, for river’s external banks and channel evolution, were assessed by processing Landsat ETM+ images in ArcGIS tool, and their inter-relationship is evaluated through regression analysis. The results revealed that the major morphological changes were triggered by the flood events occurred during the high flow or Monsoon season (July–September), whereas the flood events of similar magnitude occurring during low flow season (October–March) did not induce such changes. Mostly, the erosion remained limited to the middle part of the reach,where the branch channel flows along the bank. The average annual bank erosion rates are much higher as compared with a global scale. Data analysis showed a strong correlation between the mean high flows and total bank erosion indicating that Monsoon seasonal flows and floods are responsible for bank erosion. The present study further identifies the river bank locations highly susceptible to erosion by developing the correlation between bank erosion and branch channel progression. Strong correlation for bank erosion could be established with the shift of branch channels position flowing along the banks in braided reaches of sand bed rivers. However, the presence of sand bars along the river banks resulted in reduced erosion that weakens this relationship. The findings of the present study can help develop better understanding about the bank erosion process and constitute a key element to inform and improve river bank management
    corecore