1- Water Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Abstract: (46 Views)
Abstract
Introduction and Objective: Reservoirs play a vital role in supplying drinking water, supporting agricultural demands, and mitigating floods. Consequently, continuous monitoring of their geometric characteristics and storage capacity is essential. Progressive sedimentation—often influenced by hydrological variations and flood events—alters the reservoir morphology and reduces its effective storage volume. Although hydrographic surveys can update the initial area–elevation–volume curve, such surveys are time-consuming, costly, and operationally demanding. Remote sensing has therefore emerged as a practical and economical alternative for tracking reservoir changes.
Material and Methods: Negarestan Dam (Kabudval) is located on the Qara Su (Zarin Gol) river, and 45 km east of the city of Gorgan in the Golestan province. In this study, Landsat-8 satellite images were collected and pre-processed. Five spectral water indices (NDWI-McFeeters, NDWI-Gao, MNDWI, AWEIsh, and TCWet) were generated to delineate the water–land boundary. After validating their accuracy, MNDWI was selected as the most reliable index for extracting the water surface area. To address the limitations of linear and polynomial models in reconstructing the area–elevation relationship, a hypsometric curve was developed using the modified Strahler method. Surface areas corresponding to different water levels were obtained from this curve, and the prismoidal formula was then applied to compute the water volume between consecutive elevations and derive the current storage capacity of the Negarestan reservoir.
Results:
The evaluation of water indices showed that MNDWI provided the highest accuracy, with an error of less than 5%. A comparison between the current and initial capacities of the reservoir revealed that, over approximately nine years, its volume decreased from about 24.19 million m³ to around 20.85 million m³. This reduction corresponds to an average annual sedimentation rate of nearly 1.5%, which is almost twice the global average reported by ICOLD. The results also indicated that the average bed elevation of the reservoir has risen by roughly 9 meters due to sediment accumulation.
Conclusion:
Integrating the modified hypsometric approach with satellite observations offers a precise, low-cost, and rapid method for estimating current reservoir storage and assessing sedimentation impacts. This technique provides a practical tool for periodic monitoring and long-term management of dam reservoirs. Based on the findings and assuming constant climatic conditions, the remaining useful life of the Negarestan reservoir is estimated to be approximately 53 years.onsidering the increasing importance of water resources management, including dam reservoirs, in this study, a fast and inexpensive method based on remote sensing is used to calculate the volume of water stored in dam reservoirs and estimate the useful life. They were presented. In addition to the appropriate accuracy, this method was able to overcome the limitations of the previous methods in estimating the volume of accumulated sediment in the deep parts of the reservoir and can be used for the correct management of water resources.
Introduction and Objective: Reservoirs play a vital role in supplying drinking water, supporting agricultural demands, and mitigating floods. Consequently, continuous monitoring of their geometric characteristics and storage capacity is essential. Progressive sedimentation—often influenced by hydrological variations and flood events—alters the reservoir morphology and reduces its effective storage volume. Although hydrographic surveys can update the initial area–elevation–volume curve, such surveys are time-consuming, costly, and operationally demanding. Remote sensing has therefore emerged as a practical and economical alternative for tracking reservoir changes.
Material and Methods: Negarestan Dam (Kabudval) is located on the Qara Su (Zarin Gol) river, and 45 km east of the city of Gorgan in the Golestan province. In this study, Landsat-8 satellite images were collected and pre-processed. Five spectral water indices (NDWI-McFeeters, NDWI-Gao, MNDWI, AWEIsh, and TCWet) were generated to delineate the water–land boundary. After validating their accuracy, MNDWI was selected as the most reliable index for extracting the water surface area. To address the limitations of linear and polynomial models in reconstructing the area–elevation relationship, a hypsometric curve was developed using the modified Strahler method. Surface areas corresponding to different water levels were obtained from this curve, and the prismoidal formula was then applied to compute the water volume between consecutive elevations and derive the current storage capacity of the Negarestan reservoir.
Results:
The evaluation of water indices showed that MNDWI provided the highest accuracy, with an error of less than 5%. A comparison between the current and initial capacities of the reservoir revealed that, over approximately nine years, its volume decreased from about 24.19 million m³ to around 20.85 million m³. This reduction corresponds to an average annual sedimentation rate of nearly 1.5%, which is almost twice the global average reported by ICOLD. The results also indicated that the average bed elevation of the reservoir has risen by roughly 9 meters due to sediment accumulation.
Conclusion:
Integrating the modified hypsometric approach with satellite observations offers a precise, low-cost, and rapid method for estimating current reservoir storage and assessing sedimentation impacts. This technique provides a practical tool for periodic monitoring and long-term management of dam reservoirs. Based on the findings and assuming constant climatic conditions, the remaining useful life of the Negarestan reservoir is estimated to be approximately 53 years.onsidering the increasing importance of water resources management, including dam reservoirs, in this study, a fast and inexpensive method based on remote sensing is used to calculate the volume of water stored in dam reservoirs and estimate the useful life. They were presented. In addition to the appropriate accuracy, this method was able to overcome the limitations of the previous methods in estimating the volume of accumulated sediment in the deep parts of the reservoir and can be used for the correct management of water resources.
Type of Study: Research |
Subject:
مديريت حوزه های آبخيز
Received: 2024/08/11 | Accepted: 2026/02/25
Received: 2024/08/11 | Accepted: 2026/02/25
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