Shoeb R. Alam

Simulation and validation of fish thermal DO habitat in north-central US lakes under different climate scenarios

Fish habitat in lakes is strongly constrained by water temperature and available dissolved oxygen (DO). Suitable fish habitat for three fish assemblages (cold-, cool-, and warm-water) in Minnesota (US) lakes was therefore determined from simulated daily water temperature and dissolved oxygen profiles. A total of 27 types of lakes were simulated under past (1961‐1979) and a projected 2CO2 climate scenarios. The projected climate scenario was derived from the output of the Canadian Climate Center General Circulation Model for a doubling of atmospheric CO2. A verified, process-oriented, unsteady and one-dimensional (vertical) year-round lake water quality model (MINLAKE96) was used for the temperature and DO simulations, which were run in a continuous mode over 19 years. Water temperature and DO criteria for survival and good-growth of each fish guild were provided by the United States Environmental Protection Agency. Simulated suitable fish habitats were compared with fish observations in 3002 Minnesota lakes. Winterkill was simulated to occur in shallow eutrophic and mesotrophic lakes under past climate conditions, and predicted to disappear under the projected 2 CO2 climate scenario due to a shortening of the ice cover period. Sensitivity of the simulated winterkill to three DO survival limits was analyzed. A lower DO (less than 0.5 mg:1) limit for winterkill produced better agreement with a fish observation database than higher limits. Dependence of the simulated good-growth habitat areas (GGHA) and volumes (GGHV) on the geometry (surface area and maximum depth) and trophic state of a lake was also examined. Fish habitat parameters were found to depend more strongly on geometry and less on trophic state. Climate change is projected to increase GGHA in seasonaly stratified (medium-depth and deep) lakes on the average by 50 and 115% for cool-water and warm-water fish guilds, respectively. It is also projected that cold-water fish species will have a small percentage loss in weakly stratified (medium-depth) lakes, but a small percentage gain of GGHA in deep, strongly stratified lakes.

Projecting the Impact of Climatic Change on Coldwater Fish Habitat in Minnesota Lakes

Climate warming would alter water temperature and dissolved oxygen (DO) characteristics of lakes. These changes can be expected to have an effect on fish populations. A process-oriented, dynamic, one-dimensional year-round lake water quality model was developed and applied to simulate daily temperature and DO profiles in Minnesota lakes over 48 (1961 to 2008) or 18 (1991 to 2008) years, depending on weather data availability. The model was calibrated with data from 28 study lakes, and the average standard error of estimate against measured data was 1.47 o C for water temperature and 1.50 mg/L for DO. Projected future climate scenarios were based on the output of the Coupled Global Climate Model (CGCM), CCCma CGCM 3.1 from the Canadian Climate Centre for Climate Modeling and Analysis (CCCma), and the Model for Interdisciplinary Research on Climate, MIROC 3.2 developed in Japan. Simulated water temperature and DO profiles under past and projected future climate conditions were used to identify coldwater fish habitat in the 28 Minnesota lakes. The purpose of the study was to identify refuge lakes for cisco (tullibee), a coldwater fish species, under climate warming scenarios. Cisco is a food source for predatory sport fish species such as walleye and northern pike. Suitable coldwater fish habitat was identified by two methods: (1) a constant upper (lethal) temperature and a lower DO survival limit over the entire simulation period, or (2) variable temperature and DO survival limits based on observed fish mortality. Results obtained by both fish habitat models indicate that 19 deep, seasonally stratified, mesotrophic or oligotrophic lakes located in north or north-central Minnesota can support coldwater fish habitat under both past and future climate scenarios, and these lakes are candidates of refuge lakes. Once refuge lakes are identified, lake watershed protection efforts can be initiated at refuge lakes to prevent deterioration of water quality in these lakes by anthropogenic activities. The presentation will cover the lake water quality model development and calibration, the fish habitat model development, the application of both models to 28 lakes, the simulation results and the implications for watershed management to prevent other deteriorations of coldwater fish habitat.

Numerical Simulations of Efficiency of Curb-Opening Inlets

The geometry of highway pavement and drainage inlets, especially cross slope, longitudinal slope, and local depression and transition length, usually determine the highway surface drainage capacity. In this study, a three-dimensional computational fluid dynamics (CFD) software, FLOW-3D, is used to develop models simulating unsteady, free-surface, shallow flow through curb-opening inlets, thereby demonstrating that an advanced CFD model can be used as a virtual laboratory to evaluate performance (i.e., inlet efficiency) of curb-opening inlets with different geometry conditions. Predicted intercepted flow and inlet efficiency agree well with laboratory measurements. Flow simulations were extended to smaller cross slopes for which laboratory tests were not conducted but which can occur in a highway transition.

Flow Simulations for Curb Opening Inlets with Different Longitudinal and Cross Slopes

Proper highway drainage is essential to ensure safe and comfortable conditions for the road users. The highway pavement and inlet geometry, especially cross slope and longitudinal slope and local depression and transition length, usually determine the highway surface drainage capacity. In this study, FLOW-3D is utilized to model the unsteady free-surface flow through curb opening inlets with different longitudinal and cross slopes. FLOW-3D, developed by the Flow Science, Inc., is a three-dimensional computational fluid dynamics software that can be utilized as “Virtual Lab” to study complex flow problems. FLOW-3D utilizes a true volume of fluid method (TruVOF) to compute free surface motion and the fractional area/volume obstacle representation (FAVOR) technique to model complex geometric regions. Flow characteristics near curb opening inlets are carefully examined. Inlet efficiency is determined from flow simulation results for the inlets with various longitudinal and cross slopes, especially for small slopes where laboratory tests were not able to be conducted. Inlet efficiencies for curb opening inlets with different transitional lengths before and after the inlet are examined using FLOW-3D simulation models. Simulation results are compared with laboratory observations with good agreement.