Journal of Natural Environment

Modeling of river water qualitative changes under Voshmgir dam removal condition, Gorganrud River

Document Type : Research Paper

Authors

Department of Irrigation and Reclamation Engineering, Faculty of Agriculture, University of Tehran, Karaj, Iran

10.22059/jne.2023.352315.2506

Abstract

Dam removal is one of the methods of restoring the river ecosystem. The decision to remove a dam is based on the multidisciplinary indicators and the type of dam body and its location, as well as the downstream conditions and the type of dam removal method. In the present study, the removal of the Voshmgir Dam on the Gorganrud River, Iran, was considered, because of the high volume of sediment deposition in the reservoir and the loss of its useful life. Three scenarios were selected for the removal of the dam: 1- complete removal; 2- stepped removal of the spillway; and 3- removal with stable sediments. In the first step, numerical modeling for river morphological changes was performed using the HEC-RAS model for unsteady flows with sediment transport. The erosion and sedimentation processes were simulated in six reaches (from the Voshmgir Dam to the Caspian Sea), with total length of 128 km. The results indicated that the second scenario (stepped removal of the spillway) is the best alternative due to the gradual processes of river-bed changes. In the present research, the two-dimensional hydrodynamic and water quality model CE-QUAL-W2 is used for qualitative modeling of Gorganrud River in three scenarios of dam removal, within 128 km downstream of Vashmgir dam to the Caspian Sea Estuary. Qualitative modeling was performed for the existing conditions of Gorganrud (without removing the Vashmgir dam) at two hydrometric stations of Aqqala (68 km downstream of the Vashmgir dam) and and Basirabad (112 km downstream of Vashmgir Dam), where a set of water level and water-quality data was available for model calibration. Model results are presented in the period of rapid river changes after dam removal up to 60 days. Based on the results of qualitative modeling, the amount of dissolved oxygen (DO) has increased in three scenarios of dam removal in two sections of the river (Aqqala and Basirabad). The amount of biochemical oxygen demand (BOD) in the first scenario (complete removal) and the second (stepping removal) has increased slightly (less than 10% of the river conditions before removal). In the third scenario (removal with stable deposition), no significant change in BOD occurred. In three scenarios and in both study periods, the pH changed very little in the two periods, before and after the removal of the dam. The total amount of soluble solids (TDS) in the early days of the simulation is equal to or greater than that before removal. The TDS rate is to be decreased by time. The overall results indicated that the second scenario of the dam removal (i.e. stepped removal of the spillway) is the best alternative due to the less impacts on the river-bed changes, and the gradual processes of river-ecosystem rehabilitation.

Keywords

Bednarek, A.T., 2003. Undamming Rivers: A review of the ecological impacts of dam removal. Journal of Environmental Management 62(2), 201-232.
Bellmore, J.R., Duda, J.J., Craig, L.S., Greene, S.L., Torgersen, C.E., Collins, M.J., & Vittum, K. (2017). Status and trends of dam removal research in the United States. Wiley Interdisciplinary Reviews: Water 4(2), e1164.
Bijker, W.E., 2006. Dikes and Dams, Thick with Politics. Journal of Isis, 98(1), 109-123.
Emamgholi, Z., Yasi, M., 2020. Impacts of variation of river geometry on flowing water quality (Case Study: Ghezel Ozan River). Journal of Hydraulics 14(4), 1-17. (In Persian)
Foley, M.M.,  Bellmore, J,R., O'Connor, J.E., Duda, J.J., East, A.E., Grant, G.E., Anderson, C.W., 2017. Dam removal: Listening in. Journal of Water Resources Research 53(7), 5229-5246.
Germaine, M.A., Lespez, L., 2017. The Failure of the largest project to dismantle hydroelectric dams in Europe: (Sélune River, France, 2009-2017). Water Alternatives 10, 655-676.
Ghaffari, S., Yasi, M., Farhoudi, J., 2022. Simulation of river morphological changes under Voshmgir Dam removal condition- Gorganrud River. Iranian Journal of Watershed Management Science and Engineering 16(56), 12-21. (In Persian).
Graf, W.L., 2006. Downstream hydrologic and geomorphic effects of large dams on American rivers. Journal of Geomorphology 79(3-4), 336-360.
Habel, M., Mechkin, K., Podgorska, K., Saunes, M., Babiński, Z., Chalov, S., Absalon, D., Podgórski, Z., Obolewski, K., 2020. Dam and reservoir removal projects: a mix of social-ecological trends and cost-cutting attitudes. Scientific Reports 10(1), 192-210.
Kannel, P.R., Leea, S., Lee, Y.S., Kanel, S.R., Pelletier, G.J., 2007. Application of automated QUAL2KW for water quality modeling and management in the Bagmati River, Nepal. Journal of Ecological Modeling 202, 503517.
Ligon, F., Dietrich, W., Trush, W., 1995. Downstream ecological effects of dams. Journal of BioScience 45(3), 183-192.
Lindenschmidt, K.E., Carr, M.K., Sadeghian, A., 2019. CE-QUAL-W2 model of dam outflow elevation impact on temperature, dissolved oxygen and nutrients in a reservoir. Journal of Scientific Data 6, 312, 1-7.
Macbroom, J., Schiff, R., 2013. Sediment Management at Small Dam Removal Sites. GSA Reviews in Engineering Geology 21, 67-79.
Maingi, J. K., Marsh, S.M., 2002. Quantifying hydrologic impacts following dam construction along the Tana River, Kenya. Journal of Arid Environments 50, 53-79.
Moriasi, D.N., Arnold, J.G., Van Liew, M.W., Bingner, R.L., Harmel, R.D., Veith, T.L., 2007. Model evaluation guidelines for systematic quantification of accuracy in watershed simulations. Journal of American Society of Agricultural and Biological Engineers 50(3), 885-900.
Pelletier, G.J., Chapra, S.C., 2008. QUAL2KW, theory and documentation: A modeling framework for simulating river and stream water quality. Department of Ecology Publications Distributions Office. Publication 08-03.
Poff, N., Zimmerman, J., 2010. Ecological responses to altered flow regimes: A Literature Review to Inform the Science and Management of Environmental Flows. Journal of Freshwater Biology 55, 194-205.
Poff, N.L., Hart, D.D., 2002. How dams vary and why it matters for the emerging science of dam removal. Journal of Bioscience 52, 659-668.
Poulos, H.M., Chernoff, B., 2016. Effects of Dam Removal on Fish Community Interactions and Stability in the Eightmile River System, Connecticut, USA. Environmental Management 59, 249-263.
Rafiee, M.; Ali, A., Mohammad, A., Moazed, H., Lyon, S.W., Jaafarzadeh, N., 2013. A case study of water quality modeling of the Gargar River. Iranian Journal of Hydraulic Structures 1(2), 10-22. (In Persian)
Roberts, S.J., Gottgens, J.F., Spongberg, A.L., Evans, J.E., Levine, N.S., 2007. Assessing potential removal of low-head dams in urban settings: An example from the Ottawa River, NW Ohio. Journal of Environmental Management 39, 113-124.
Sazepardazi-Iran Consulting Engineers, 2007. Golestan Dam, Bostan and Vashmgir Dam breakdown studies. Published by Golestan Water Affair, Iran. 270 p. (In Persian)
Shuman, J.R., 1995. Environmental considerations for assessing dam removal alternatives for river restoration. Regulated Rivers. Journal of Research & Management 11(3-4), 249-261.
Sneddon, C., Barraud, R., Germaine, M.A., 2017. Dam removals and river restoration in international perspective. Journal of Water Alternatives 10, 648-654.
Talebzadeh, J., 2010. Analysis of reservoir sediment transport, while removing the dam, using numerical modeling. M.Sc. Thesis. Shiraz University. 110 p. (In Persian).
Wana, Y., Suna, D., Labadie, J., 2014. Modelling evaluation of dam removal in the context of river ecosystem restoration. Journal of River Research and Application 31(9), 1119-1130.
Water Institute-University of Tehran, 2012. Golestan Dam, Bostan and Vashmgir Dam Breakdown Studies. Published by Golestan Water Affair, Iran. 240 p. (In Persian)
 
Journal of Natural Environment
Volume 75, Special Issue Coastal and Marine Environment
February 2023
Pages 227-242