Simulations of water quality and oxythermal cisco habitat in Minnesota lakes under past and future climate scenarios Xing Fang, Shoeb R. Alam, Heinz G. Stefan, Liping Jiang, Peter C. Jacobson and Donald L. Pereira ABSTRACT A deterministic, process-oriented, dynamic and one-dimensional year-round lake water quality model, MINLAKE2010, was developed for water temperature (T ) and dissolved oxygen (DO) simulations to study impacts of climate warming on lake water quality and cisco fish habitat. The DO model is able to simulate metalimnetic oxygen maxima in vertical DO profiles of oligotrophic lakes. The model was calibrated with profile data from the 28 study lakes in Minnesota; two-thirds of them are deep mesotrophic/oligotrophic lakes that support cisco, a coldwater fish species. The average standard error of estimate against measured data was 1.47 W C for T and 1.50 mg/L for DO. Oxythermal habitat parameter TDO3 (T at DO ¼ 3 mg/L) was determined from simulated daily T and DO profiles under past and future climate scenarios in the 28 study lakes. Average annual maximum TDO3 (TDO3 AM ) for the 28 study lakes is projected to increase on the average of 3.2 W C under the MIROC 3.2 future scenario, while the occurrence day of TDO3 AM is not much different under past and future climate scenarios. Both physical processes (mixing characteristics related to lake geometry ratio) and trophic status control temperature and DO characteristics and then affect cisco habitat in a lake. Xing Fang (corresponding author) Liping Jiang Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA E-mail: xing.fang@auburn.edu Shoeb R. Alam Department of Civil Engineering, Lamar University, Beaumont, TX 77710, USA Heinz G. Stefan St. Anthony Falls Laboratory, Department of Civil Engineering, University of Minnesota, Minneapolis, MN 55414, USA Peter C. Jacobson Minnesota Department of Natural Resources, 14583 County Road 19, Detroit Lakes, MN 56501, USA Donald L. Pereira Minnesota Department of Natural Resources, 500 Lafayette Road, St. Paul, MN 55155, USA Key words | climate change, dissolved oxygen, fish habitat, lakes, simulation model, water quality INTRODUCTION Water quality is a critical issue because of its direct influ- ence on public health and biological integrity of natural resources. Water resources managers and professionals are concerned for the potential significance and impacts of climate change on inland aquatic ecosystems, i.e., streams, lakes, and reservoirs. To make projections of water quality and fish habitat in lakes under future climate scenarios, numerical simulation models are very useful, if not indispensable. To project potential effects of climate change on water quality and ecology of fresh water sys- tems, deterministic simulation models have been developed and applied to the Laurentian Great Lakes (Blumberg & Di Toro ); reservoirs (Chang et al. ) and lakes in north-temperate regions (De Stasio et al. ; Stefan et al. ); and lakes in the contiguous USA (Fang & Stefan ). The goal of the study described herein was to simulate daily water temperature (T ) and dissolved oxygen (DO) pro- files in cisco lakes in Minnesota, and then to project lake water quality conditions under projected future climate warming in order to identify cisco refuge lakes in Minnesota. A ‘refuge lake’ is a lake that has supported cisco under past (historical) climate conditions and is projected to pro- vide cisco habitat under future climate scenarios. The Minnesota Department of Natural Resources (MN DNR) has sampled cisco from 648 lakes in netting assessments since 1946 (Minnesota DNR files). The cisco lakes are scattered throughout much of the central and northern 375 © IWA Publishing 2012 Water Quality Research Journal of Canada | 47.3-4 | 2012 doi: 10.2166/wqrjc.2012.031 Downloaded from http://iwaponline.com/wqrj/article-pdf/47/3-4/375/163545/375.pdf by guest on 24 June 2022