@misc{12212, abstract = {{Water quality and hypoxia in lakes and reservoirs are strongly associated with water renewal. Yet vertical water exchange is still not fully understood and challenging to evaluate in highly dynamic systems. Here, we applied a scaling approach using the vertical timescale, vertical water age (VWA), defined as time since a water parcel last touched the water surface. We established a 3D hydrodynamic-based age model to quantify the vertical water renewal in Xiangxi Bay, a tributary bay of the Three Gorges Dam. The integrated effects of hydrodynamic processes like stratification, intruding density currents from the mainstream, and upstream inflow on the vertical renewal were accounted for. Results indicated that the spatial–temporal distribution of VWA in Xiangxi Bay depended on stratification and forms of intruding density currents. Age was large in spring and summer, and small in autumn and winter, reaching a maximum of 25 days in April. The vertical water renewal was faster during bottom intrusions from the mainstream than during middle and surface intrusions. At times, the epilimnion contained old water due to circulations, and the hypolimnion contained young water due to upstream flushing. In contrast to natural lakes, the bottom water was often younger than overlying intermediate waters. This demonstrated that mixed layer depth was insufficient to fully capture the vertical exchange in riverine systems with significant surface/bottom intrusion. The findings suggested VWA as a quantitative measure of vertical water transport in highly dynamic systems and its usability for environmental water management.}}, author = {{Gai, Bo and Boehrer, Bertram and Sun, Jian and Li, Yuanyi and Lin, Binliang and Shatwell, Tom}}, booktitle = {{Journal of Hydrology}}, issn = {{1879-2707}}, keywords = {{Vertical water renewal, Water age, Thermal stratification, Hypoxia, 3D hydrodynamic-based age model, Water environmental management}}, number = {{3}}, publisher = {{Elsevier BV}}, title = {{{Vertical water age and water renewal in a large riverine reservoir}}}, doi = {{10.1016/j.jhydrol.2024.130701}}, volume = {{631}}, year = {{2024}}, } @misc{12215, abstract = {{Water-level reduction frequently occurs in deep reservoirs, but its effect on dissolved oxygen concentration is not well understood. In this study we used a well-established water quality model to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir, Germany. We then systematically elucidated the potential of selective withdrawal to control hypoxia under changing water levels. Our results documented a gradual decrease of hypolimnetic oxygen concentration under decreasing water level, and hypoxia occurred when the initial level was lower than 410 m a.s.l (71 m relative to the reservoir bottom). We also suggested that changes of hypoxic region, under increasing hypolimnetic withdrawal discharge, followed a unimodal trajectory with the maximum hypoxic area projected under the discharge between 3 m3/sec and 4 m3/sec. Besides, our results illustrated the extent of hypoxia was most effectively inhibited if the withdrawal strategy was applied at the end of stratification with the outlet elevation at the deepest part of the reservoir. Moreover, hypoxia can be totally avoided under a hybrid elevation withdrawal strategy using surface withdrawal during early and mid stratification, and deep withdrawal at the end of stratification. We further confirmed the decisive role of thermal structure in the formation of hypoxia under water-level reduction and withdrawal strategies. We believe the conclusions from this study can be applied to many deep waters in the temperate zone, and the results should guide stakeholders to mitigate negative impacts of hypoxia on aquatic ecosystems.}}, author = {{Mi, Chenxi and Rinke, Karsten and Shatwell, Tom}}, booktitle = {{Journal of Environmental Sciences}}, issn = {{1878-7320}}, keywords = {{Hypoxia, Water-level reduction, Hypolimnetic water withdrawal, Stratification phenology, Water quality simulation, Sediment oxygen demand}}, number = {{12}}, pages = {{127--139}}, publisher = {{Elsevier BV}}, title = {{{Optimizing selective withdrawal strategies to mitigate hypoxia under water-level reduction in Germany's largest drinking water reservoir}}}, doi = {{10.1016/j.jes.2023.06.025}}, volume = {{146}}, year = {{2024}}, } @misc{12225, abstract = {{Lake Sevan is the largest freshwater body in the Caucasus region, situated at an altitude of 1,900 m asl. While it is a major water resource in the whole region, Lake Sevan has received little attention in international limnological literature. Although recent studies pointed to algal blooms and negative impacts of climate change and eutrophication, the physical controls on thermal dynamics have not been characterized and model-based assessments of climate change impacts are lacking. We compiled a decade of historical data for meteorological conditions and temperature dynamics in Lake Sevan and used a one-dimensional hydrodynamic model (GLM 3.1) in order to study thermal structure, the stratification phenology and their meteorological drivers in this large mountain lake. We then evaluated the representativeness of meteorological data products covering almost 4 decades (EWEMBI-dataset: 1979-2016) for driving the model and found that these data are well suited to restore long term thermal dynamics in Lake Sevan. This established model setting allowed us to identify major changes in Lake Sevan’s stratification in response to changing meteorological conditions as expected from ongoing climate change. Our results point to a changing mixing type from dimictic to monomictic as Lake Sevan will experience prolonged summer stratification periods and more stable stratification. These projected changes in stratification must be included in long-term management perspectives as they will intensify water quality deteriorations like surface algal blooms or deep water anoxia.}}, author = {{Shikhani, Muhammed and Mi, Chenxi and Gevorgyan, Artur and Gevorgyan, Gor and Misakyan, Amalya and Azizyan, Levon and Barfus, Klemens and Schulze, Martin and Shatwell, Tom and Rinke, Karsten}}, booktitle = {{Journal of Limnology}}, issn = {{1723-8633}}, keywords = {{General Lake Model (GLM), Lake Sevan, temperature stratification, EWEMBI, climate warming}}, number = {{s1}}, publisher = {{Istituto per lo Studio degli Ecosistemi (Verbania) }}, title = {{{Simulating thermal dynamics of the largest lake in the Caucasus region: The mountain Lake Sevan}}}, doi = {{10.4081/jlimnol.2021.2024}}, volume = {{81}}, year = {{2021}}, } @misc{12239, abstract = {{The modelling community has identified challenges for the integration and assessment of lake models due to the diversity of modelling approaches and lakes. In this study, we develop and assess a one-dimensional lake model and apply it to 32 lakes from a global observatory network. The data set included lakes over broad ranges in latitude, climatic zones, size, residence time, mixing regime and trophic level. Model performance was evaluated using several error assessment metrics, and a sensitivity analysis was conducted for nine parameters that governed the surface heat exchange and mixing efficiency. There was low correlation between input data uncertainty and model performance and predictions of temperature were less sensitive to model parameters than prediction of thermocline depth and Schmidt stability. The study provides guidance to where the general model approach and associated assumptions work, and cases where adjustments to model parameterisations and/or structure are required.}}, author = {{Bruce, Louise C. and Frassl, Marieke A. and Arhonditsis, George B. and Gal, Gideon and Hamilton, David P. and Hanson, Paul C. and Hetherington, Amy L. and Melack, John M. and Read, Jordan S. and Rinke, Karsten and Rigosi, Anna and Trolle, Dennis and Winslow, Luke and Adrian, Rita and Ayala, Ana I. and Bocaniov, Serghei A. and Boehrer, Bertram and Boon, Casper and Brookes, Justin D. and Bueche, Thomas and Busch, Brendan D. and Copetti, Diego and Cortés, Alicia and de Eyto, Elvira and Elliott, J. Alex and Gallina, Nicole and Gilboa, Yael and Guyennon, Nicolas and Huang, Lei and Kerimoglu, Onur and Lenters, John D. and MacIntyre, Sally and Makler-Pick, Vardit and McBride, Chris G. and Moreira, Santiago and Özkundakci, Deniz and Pilotti, Marco and Rueda, Francisco J. and Rusak, James A. and Samal, Nihar R. and Schmid, Martin and Shatwell, Tom and Snorthheim, Craig and Soulignac, Frédéric and Valerio, Giulia and van der Linden, Leon and Vetter, Mark and Vinçon-Leite, Brigitte and Wang, Junbo and Weber, Michael and Wickramaratne, Chaturangi and Woolway, R. Iestyn and Yao, Huaxia and Hipsey, Matthew R.}}, booktitle = {{Environmental modelling & software with environment data news }}, issn = {{1873-6726}}, keywords = {{Lake model, Stratification, GLM, Model assessment, Global observatory data, Network science}}, number = {{4}}, pages = {{274--291}}, publisher = {{Elsevier Science}}, title = {{{A multi-lake comparative analysis of the General Lake Model (GLM): Stress-testing across a global observatory network}}}, doi = {{10.1016/j.envsoft.2017.11.016}}, volume = {{102}}, year = {{2018}}, } @misc{12242, abstract = {{Hutchinson and Löffler's (1956) classification of lakes based on the seasonal thermal mixing regime has become a cornerstone of any analysis of lakes as elements of the earth surface. Until now however the lake classification has lacked a physically sound quantitative criterion distinguishing between two fundamental lake types: thermally stratified during a large portion of the year (mono- and dimictic) and predominantly mixed to the bottom (polymictic). Using the mechanistic balance between potential and kinetic energy we review the different formulations of the Richardson number to derive a generalized scaling for seasonal stratification in a closed lake basin. The scaling parameter is the critical mean basin depth, Hcrit, that delineates lakes that mix regularly from those that stratify seasonally based on lake water transparency, lake length, and an annual mean estimate for the Monin-Obukhov length. We validate the scaling on available data of lakes worldwide using logistic regression. The scaling criterion consistently described the mixing regime significantly better than either the conventional unbounded basin scaling or a simple depth threshold. Thus, the generalized scaling is universal for freshwater lakes and allows the seasonal mixing regime to be estimated without numerically solving the heat transport equations.}}, author = {{Kirillin, G. and Shatwell, Tom}}, booktitle = {{Earth-Science Reviews}}, issn = {{0012-8252}}, keywords = {{Richardson number, Lake classification, Seasonal stratification, Dimixis, Polymixis, Water transparency, Lake databases, Lake modeling, Secchi depth}}, pages = {{179--190}}, publisher = {{Elsevier BV}}, title = {{{Generalized scaling of seasonal thermal stratification in lakes}}}, doi = {{10.1016/j.earscirev.2016.08.008}}, volume = {{161}}, year = {{2016}}, } @misc{12249, abstract = {{We investigated the combined effects of thermal pollution from a nuclear power plant (NPP) and regional climate warming on the thermal regime of a lake. For this purpose, we used the lake model FLake and analyzed 50 years of temperature data from Lake Stechlin, Germany, which served as the cooling water reservoir for the Rheinsberg NPP from 1966 until 1990. Both modeling and statistical data analysis revealed a strong influence of the NPP cooling water discharge on the lake water temperatures and the vertical stability of the water column. A remarkable effect of thermal pollution consisted of strong vertical mixing in winter produced by the discharge of warm water into the lake when ambient water temperatures were below 4 °C. This effect caused a significant increase in the deep hypolimnion temperatures and a corresponding decrease of the vertical stability in the summer. In turn, climate warming had the opposite effect on the summer stability by increasing lake surface temperatures. Both the thermal pollution and climate change increased the duration of the summer stratification period. Our results suggest that industrial thermal pollution in temperate lakes during winter is stored in the deep water column until the next winter, whereas heat added in the summer dissipates relatively rapidly into the atmosphere. Accordingly, the winter thermal pollution could have a long-lasting effect on the lake ecology by affecting benthic biogeochemical processes.}}, author = {{Kirillin, Georgiy and Shatwell, Tom and Kasprzak, Peter}}, booktitle = {{Journal of Hydrology}}, issn = {{1879-2707}}, keywords = {{Industrial thermal pollution, Global warming, Lake stratification, FLake model}}, number = {{7}}, pages = {{47--56}}, publisher = {{Elsevier BV}}, title = {{{Consequences of thermal pollution from a nuclear plant on lake temperature and mixing regime}}}, doi = {{10.1016/j.jhydrol.2013.05.023}}, volume = {{496}}, year = {{2013}}, }