Assessing the impacts of thermal stratification on water quality and strategies for and reducing cold water emissions
Subject Areas : Chemistry and Chemical Engineering of all specializationsNasim Mosakhani 1 , Ahmad Asl hashemi 2 , Gholam Hossein Safari 3 *
1 - Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
2 - Department of Environmental Health Engineering, Faculty of Health, Tabriz University of Medical Sciences, Tabriz, Iran
3 - Department of Environmental Health Engineering, Faculty of Health, Tabriz University of Medical Sciences, Tabriz, Iran. Health & Environment Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Keywords: Thermal stratification, reservoir water quality, cold-water release, cyanobacterial blooms, selective withdrawal, bubble plume systems, surface mixers.,
Abstract :
Thermal stratification is one of the critical challenges in reservoir management, arising from temperature gradients in the water column that lead to the formation of distinct layers with varying physical and chemical properties. This phenomenon significantly reduces dissolved oxygen levels in deeper water layers and contributes to several environmental issues, including the release of cold water downstream, increased concentrations of heavy metals such as iron and manganese, and the proliferation of cyanobacterial blooms.
This article presents a systematic review aimed at collecting, analyzing, and comprehensively evaluating current technologies and methods for mitigating cold-water release from reservoirs caused by thermal stratification. A thorough literature search was conducted using reputable databases such as Web of Science, Scopus, Google Scholar, and specialized databases in water and environmental engineering. Relevant keywords—such as “reservoir destratification,” “cold-water release from dams,” “bubble columns,” “surface mixers,” “multi-level selective withdrawal,” and “GELI technology”—were used in both Persian and English. The study begins by reviewing natural processes of thermal stratification and destratification in reservoirs. It then assesses the impacts of stratification on water quality, including dissolved oxygen depletion, cold-water discharge, elevated heavy metal concentrations, and toxic algal growth. Subsequently, three common technical approaches for mitigating stratification and cold-water release are introduced and compared: selective withdrawal using multi-level intake structures, the use of bubble plume systems, and surface mixing devices. The findings suggest that the selection of an appropriate method depends on reservoir characteristics, management objectives, and implementation costs. Among the options, bubble plume systems are often considered an effective and practical solution due to their ability to enhance oxygenation, reduce metal concentrations, and suppress algal blooms.
[1] Nazrehia M., Danaei A., Hashemi SH., Izad Doostda, AH. Prediction of thermal stratification of the dam under construction in Bakhtiari using the CE-QUAL-W2 model, Environment, 36 (2011) 1-8.
[2] Fazeli M., Attari J., Hashemi S.H., Jumaegi A. Investigation of methods to prevent thermal stratification in the Latian Dam Lake (first stage of feasibility study), Tehran Regional Water Joint Stock Company, (2011) (in Persian).
[3] Woolway RI, Merchant CJ. Worldwide alteration of lake mixing regimes in response to climate change. Nature Geoscience, 12(2019) 271-6.
[4] Houshmand Ayini A. Investigation of the stratification phenomenon in reservoirs and methods for preventing it, First Regional on Civil Engineering, Joibar (2011) (In Persian).
[5] Water Science Engineering Specialized Association, Thermal Stratification, (2012). available in http:// aterse.ir (In Persian).
[6] Zargarpour H., Gharavi, M., Jafar, D. Thermal stratification in successive reservoirs - a case study of Karun 1, 2 and 3 dam reservoirs, Iranian Water Resources Research, 3 (2007) (In Persian).
[7] Mohammadnejad, B., Bayramali, P., Navid B. Simulation of nutrient orientation of Mahabad Dam reservoir using two-dimensional CE-QUAL-W2 model. Journal of Civil and Environmental Engineering, University of Tabriz, 44 (2015) 107-115. (In Persian).
[8] Hayes NM, Deemer BR, Corman JR, Razavi NR, Strock KE. Key differences between lakes and reservoirs modify climate signals: A case for a new conceptual model. Limnology and Oceanography Letters, 2(2017) 47-62.
[9] Bengtsson L. Classification of Lakes from Hydrological Function, in Encyclopedia of Lakes and Reservoirs, (2012)163–164.
[10] Herschy RW. Dams, Classification, in Encyclopedia of Earth Sciences Series, (2012) 200–207.
[11] Poff NL, Hart DD. How dams vary and why it matters for the emerging science of dam removal: an ecological classification of dams is needed to characterize how the tremendous variation in the size, operational mode, age, and number of dams in a river basin influences the potential for restoring regulated rivers via dam removal. BioScience, 52(2002) 659-68.
[12] Miles NG, West RJ. The use of an aeration system to prevent thermal stratification of a freshwater impoundment and its effect on downstream fish assemblages. Journal of fish Biology, 78(2011) 945-52.
[13] Gray R, Jones HA, Hitchcock JN, Hardwick L, Pepper D, Lugg A, Seymour JR, Mitrovic SM. Mitigation of cold‐water thermal pollution downstream of a large dam with the use of a novel thermal curtain. River Research and Applications, 35(2019) 855-66.
[14] Chaaya FC, Miller BM. Pindari Dam cold water pollution mitigation through artificial destratification–Monitoring network recommendations. WRL Technical Report 2022/19, UNSW Water Research Laboratory; 2023.
[15] Winton RS, Calamita E, Wehrli B. Reviews and syntheses: Dams, water quality and tropical reservoir stratification. Biogeosciences, (2019) 16(8):1657-71.
[16] Huttula T. Stratification in Lakes, in Encyclopedia of Lakes and Reservoirs, (2012) 743–747.
[17] Gibbs MM, Howard-Williams C, Sherman B, Brookes JD, Ibelings BW. Physical processes for in-lake restoration: Destratification and mixing. InLake Restoration Handbook: A New Zealand Perspective, (2019) 165-205. Cham: Springer International Publishing.
[18] Masunaga E, Komuro S. Stratification and mixing processes associated with hypoxia in a shallow lake (Lake Kasumigaura, Japan). Limnology, (2020) (2):173-86.
[19] Li N, Huang T, Li Y, Si F, Zhang H, Wen G. Inducing an extended naturally complete mixing period in a stratified reservoir via artificial destratification. Science of the Total Environment, 745 (2020) 140958.
[20] Masunaga E, Komuro S. Stratification and mixing processes associated with hypoxia in a shallow lake (Lake Kasumigaura, Japan). Limnology, 21(2020) 173-86.
[21] Chaaya FC, Miller B. A review of artificial destratification techniques for cold water pollution mitigation, 2022.
Aviaeble in: ttps://www.unsw.edu.au/content/dam/pdfs/engineering/civil-environmental/water-research-laboratory/publications/WRL-TR2021-17
[22] Ryan T, Webb A, Lennie R, Lyon J. Status of cold-water releases from Victorian dams. Arthur Rylah Institute, Department of Natural Resources and Environment, Melbourne, (2001) 61.
[23] Hayes DB, Dodd HO, Lessard JO. Effects of small dams on coldwater stream fish communities. InAmerican Fisheries Society Symposium, 49 (2008) 1791, American Fisheries Society.
[24] Boys C, Miles N, Rayner T. Scoping options for the ecological assessment of cold-water pollution mitigation downstream of Keepit Dam, Namoi River. Murray–Darling Basin Authority, NSW Department of Primary Industries, 2009.
[25] Michie LE, Thiem JD, Boys CA, Mitrovic SM. The effects of cold shock on freshwater fish larvae and early-stage juveniles: implications for river management. Conservation physiology, 8 (2020) coaa092.
[26] Bryant LD, Hsu-Kim H, Gantzer PA, Little JC. Solving the problem at the source: controlling Mn release at the sediment-water interface via hypolimnetic oxygenation. Water Research, 45(2011) 6381-92.
[27] Beutel MW, Leonard TM, Dent SR, Moore BC. Effects of aerobic and anaerobic conditions on P, N, Fe, Mn, and Hg accumulation in waters overlaying profundal sediments of an oligo-mesotrophic lake. Water research, 42(2008) 1953-62.
[28] Munger ZW, Carey CC, Gerling AB, Hamre KD, Doubek JP, Klepatzki SD, McClure RP, Schreiber ME. Effectiveness of hypolimnetic oxygenation for preventing accumulation of Fe and Mn in a drinking water reservoir. Water Research, 106 (2016) 1-4.
[29] Khan K, Wasserman GA, Liu X, Ahmed E, Parvez F, Slavkovich V, Levy D, Mey J, van Geen A, Graziano JH, Factor-Litvak P. Manganese exposure from drinking water and children's academic achievement. Neurotoxicology, 33(2012) 91-7.
[30] Vieira MC, Torronteras R, Córdoba F, Canalejo A. Acute toxicity of manganese in goldfish Carassius auratus is associated with oxidative stress and organ specific antioxidant responses. Ecotoxicology and environmental safety, 78 (2012) 212-7.
[31] Hedayati A, Hoseini SM, Ghelichpour M. Acute toxicity of waterborne manganese to Rutilus caspicus (Yakovlev, 1870)–gill histopathology, immune indices, oxidative condition, and saltwater resistance. Toxicological & Environmental Chemistry, 96 (2014) 1535-45.
[32] Bormans M, Maršálek B, Jančula D. Controlling internal phosphorus loading in lakes by physical methods to reduce cyanobacterial blooms: a review. Aquatic Ecology, 50 (2016) 407-22.
[33] Ma WX, Huang TL, Li X. Study of the application of the water-lifting aerators to improve the water quality of a stratified, eutrophicated reservoir. Ecological Engineering, 83 (2015) 281-90.
[34] Visser PM, Ibelings BW, Bormans M, Huisman J. Artificial mixing to control cyanobacterial blooms: a review. Aquatic Ecology, 50 (2016) 423-41.
[35] dos Santos Silva RD, Severiano JS, de Oliveira DA, Mendes CF, Barbosa VV, Chia MA, de Lucena Barbosa JE. Spatio-temporal variation of cyanobacteria and cyanotoxins in public supply reservoirs of the semi-arid region of Brazil. Journal of Limnology, 79 (2020).
[36] Manning SR, Nobles DR. Impact of global warming on water toxicity: cyanotoxins. Current Opinion in Food Science, 18 (2017) 14-20.
[37] Lee S, Jiang X, Manubolu M, Riedl K, Ludsin SA, Martin JF, Lee J. Fresh produce and their soils accumulate cyanotoxins from irrigation water: Implications for public health and food security. Food research international, 102 (2017) 234-45.
[38] Hamilton DP, Wood SA, Dietrich DR, Puddick J. Costs of harmful blooms of freshwater cyanobacteria. Cyanobacteria: An economic perspective, 10 (2014) 245-56.
[39] Hamilton DP, Salmaso N, Paerl HW. Mitigating harmful cyanobacterial blooms: strategies for control of nitrogen and phosphorus loads. Aquatic Ecology, 50 (2016) 351-66.
[40] Slavin EI, Wain DJ, Bryant LD, Amani M, Perkins RG, Blenkinsopp C, Simoncelli S, Hurley S. The effects of surface mixers on stratification, dissolved oxygen, and cyanobacteria in a shallow eutrophic reservoir. Water Resources Research, (2022) 58(7): e2021WR030068.
[41] Preece R. Cold water pollution below dams in New South Wales: a desktop assessment. Water management Division, Department of Infrastructure, Planning and Natural Resources, (2004).
[42] Olden JD, Naiman RJ. Incorporating thermal regimes into environmental flows assessments: modifying dam operations to restore freshwater ecosystem integrity. Freshwater Biology, 55(2010) 86-107.
[43] Li N, Huang T, Mao X, Zhang H, Li K, Wen G, Lv X, Deng L. Controlling reduced iron and manganese in a drinking water reservoir by hypolimnetic aeration and artificial destratification. Science of the Total Environment, 685 (2019) 497-507.
[44] Sherman B, Todd CR, Koehn JD, Ryan T. Modelling the impact and potential mitigation of cold-water pollution on Murray cod populations downstream of Hume Dam, Australia. River Research and Applications, 23(2007) 377-89.
[45] Ingleton T, Kobayashi T, Sanderson B, Patra R, Macinnis-Ng CM, Hindmarsh B, Bowling LC. Investigations of the temporal variation of cyanobacterial and other phytoplanktonic cells at the offtake of a large reservoir, and their survival following passage through it. Hydrobiologia, 603 (2008) 221-40.
[46] Martin J, Higgins J, Edinger J, Gordon J. Energy Production and Reservoir Water Quality. American Society of Civil Engineers (2014).
[47] Bryant LD, Gantzer PA, Little JC. Increased sediment oxygen uptake caused by oxygenation-induced hypolimnetic mixing. Water research, Management-Deep Reservoir Circulation. In7th annual WIOA NSW water industry operations conference. Exhibition Park in Canberra (2013) 84-91.
48] Elliott S., Swan D. Source Water Management - Deep Reservoir Circulation, in 7th Annual
WIOA NSW Water Industry Operations Conference and Exhibition, (2013) 84–91
[49] Bryant LD, Hsu-Kim H, Gantzer PA, Little JC. Solving the problem at the source: controlling Mn release at the sediment-water interface via hypolimnetic oxygenation. Water Research, 45 (2011) 6381-92.
[50] Helfer, F. Influence of air-bubble plumes and effects of climate change on reservoir evaporation, Ph.D. Thesis, Griffith School of Engineering Science, Environment, Engineering and Technology, Griffith University, (2012) 6-27.
[51] Becker A, Herschel A, Wilhelm C. Biological effects of incomplete destratification of hypertrophic freshwater reservoir. Hydrobiologia, 559 (2006) 85-100.
[52] Lewis DM. Surface mixers for destratification and management of Anabaena circinalis, Ph.D. Thesis, School of Civil and Environmental Engineering, University of Adelaide, (2004) 221-234.
[53] Sahoo GB, Luketina D. Bubbler design for reservoir destratification. Marine and freshwater research, 54 (2003) 271-85.
[54] Cannon S. Reservoir Management: A Practical Guide. John Wiley & Sons, (2020) 17-34.
[55] Lawson R, Anderson MA. Stratification and mixing in Lake Elsinore, California: An assessment of axial flow pumps for improving water quality in a shallow eutrophic lake. Water research, 41(2007) 4457-67.
[56] Gray R. Effectiveness of cold-water pollution mitigation at Burrendong Dam using an innovative thermal curtain. University of Technology Sydney (Australia), (2016) 35-48.
[57] Mejica BN, Ebert DA, Tanaka SK, Deas ML. Managing cyanobacteria with a water quality control curtain in Iron Gate Reservoir, California. Lake and Reservoir Management, 39 (2023) 291-310.
[58] Smith CA, Read JS, Vander Zanden MJ. Evaluating the “Gradual Entrainment Lake Inverter” (GELI) artificial mixing technology for lake and reservoir management. Lake and Reservoir Management, 34 (2018) 232-43.
[59] Read JS, Shade A, Wu CH, Gorzalski A, McMahon KD. “Gradual Entrainment Lake Inverter” (GELI): A novel device for experimental lake mixing. Limnology and Oceanography: Methods, 9 (2011) 14-28.