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Factors affecting fall turnover in brackish lakes Hasanloo, Davood 2014

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      FACTORS AFFECTING FALL TURNOVER IN BRACKISH LAKES by Davood Hasanloo M.Sc., Iran University of Science and Technology 2009   A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  Master of Applied Science  in  THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES  (Civil Engineering)    The University of British Columbia (Vancouver) August 2014 © Davood Hasanloo  ii   Abstract  This study investigates fall mixing in brackish lakes. Data from the Colomac Zone 2 Pit Lake is used to study the effects of salinity structure, and the ratio of runoff plus direct precipitation to evaporation (P*/E), on fall turnover. Zone 2 Pit Lake is currently not subject to turnover, but the model CE-QUAL-W2 is used to investigate conditions under which it, or other similar lakes, might turnover in fall. Accordingly, a curve is generated which separates meromictic and holomictic states for different combinations of salinity stratification and P*/E ratios given the bathymetry of Zone 2 Pit Lake, and the meteorological forcing it was subject to in 2010. It is shown that in brackish lakes, increases in the salinity of the surface layer due to evaporation can drive turnover.              iii   Preface  I, Davood Hasanloo, was the main contributor with respect to research for the hydrodynamic modeling of Colomac Zone 2 Pit Lake, along with all other content of this thesis.             iv  Table of Contents  Abstract ..................................................................................................................................... ii Preface ...................................................................................................................................... iii Table of Contents ...................................................................................................................... iv List of Tables ..............................................................................................................................v List of Figures ........................................................................................................................... vi Notation .................................................................................................................................. viii Acknowledgements .....................................................................................................................x Dedication ................................................................................................................................. xi Introduction ................................................................................................................................1 Study Site....................................................................................................................................4 Methods ......................................................................................................................................6 Results ...................................................................................................................................... 13 Discussion ................................................................................................................................. 16 Conclusions .............................................................................................................................. 24 Bibliography ............................................................................................................................. 38         v  List of Tables  Table   1. Summary of simulations A to H                    vi   List of Figures  Fig. 1. Zone 2 Pit Lake (a) bathymetry and (b) cross section showing the location of the sampling station (raft) with meterological station and mooring.  Fig. 2. The observed (a) temperature, (b) salinity and (c) density of Z2P on 9 August 2010. These data were used as the initial condition for the base case model. The color lines in (b) illustrate the different initial salinity stratifications corresponding to different values of the salinity stratification factor, fs, used in the hypothetical model scenarios. Fig. 3. Observed (a) hourly water temperature, (b) hourly wind speed, (c) daily mean air temperature and dew point, and (d) hourly solar radiation and daily cloud cover for day 221 to 300, 9 August to 27 October 2010.  Fig. 4. Contour plot of water temperature for (a) observed and (b) modeled data, day 221 to 295, 9 August to 22 October, 2010. The surface layer depth as determined from the maximum gradient in density is shown as (a) purple dots (from observed temperature and conductivity profiles) and (b) purple line (from model data).  Fig. 5. Comparison between observed (red) and modeled (black) (a) temperature, (b) salinity and (c) density for 9 August 2010 (day 221), 8 September 2010 (day 251), 17 September 2010 (day 260) and 7 October 2010 (day 280). The surface layer is cooler and deeper with each successive profile. As the first CTD profile of 9 August 2010 is the initial condition for the model temperature, salinity and density, the observed and model profiles are the same.  Fig. 6. Dependence of meromixis in Zone 2 Pit Lake on salinity stratification factor, fs, and the ratio of effective precipitation to evaporation, P*/E. The red line marks the boundary  vii  between meromictic and holomictic regimes. The solid squares mark holomictic cases and open squares show meromictic cases. The base case represents observed condition in Zone 2 Pit during 2010. Fig. 7. (a-d) Salinity and (e-h) salinity, temperature and total stability for cases A, B, C and D. In (a-d), the surface salinity, bottom salinity and mean salinity of the lake are shown by red, dark blue and black dashed line, respectively.   Fig. 8. (a-d) Salinity and (e-h) salinity, temperature and total stability for cases A, E, F and G. In (a-d), the surface salinity, bottom salinity and mean salinity of the lake are shown by red, dark blue and black dashed line, respectively.  Fig. 9. (a and c) Expanded salinity line plots and (b and d) expanded salinity, temperature and total stability for cases B and E respectively.  Fig. 10. (a) Wind speed squared, (b) saturated vapor pressure at water surface, es, atmospheric vapor pressure, ea, difference between es and ea, (c) evaporation and precipitation rate and (d) cooling, wind stirring and evaporation fluxes for case E.  Fig. 11. Profiles of (a) salinity, (b) temperature, (c) salinity density, (d) temperature density and (e) total density between day 287.5 and 287.9 (12:00 PM and 9:36 PM, 14 October 2010). The profiles are plotted at 10 minutes intervals. The first profile is shown in red and the last one in dark blue. In (e), the red arrow marks the first profile of total density to become unstable (4:50 PM, 14 October 2010), and the black arrow marks the first profile of total density to become homogenous (6:50 PM, 14 October 2010).      viii  Notation  	                                     water thermal expansion coefficient [K-1]                                       temperature (dew point or water surface) [oC] 	                                     water density [kgm-3] ̅                                      mean density [kgm-3] 	                                 air density [kgm-3] 	                                 density at z [kgm-3] 	                           density for pure water [Kgm-3] A(0)                                 surface area [m2] A(z)                                 area of the pit at z [m2] = 8.221×10-4                density constant [kgm-3] = -3.87×10-6                density constant [kgm-3 oC-1] = 4.99×10-8                  density constant [kgm-3 oC-2]  = 0.001                       wind drag coefficient [dimensionless]                                      specific heat of water [J kg-1 K-1]                                      air vapor pressure [mm Hg]                                      saturation vapor pressure at water surface [mm Hg] fs                                       salinity stratification factor [dimensionless] f	w                                 wind function [Wm-2mm Hg-1] g                                        acceleration of gravity [m2s-1]  ix  h                                        total depth [m] ℎ                                  depth of surface layer [m]  H                                     evaporative heat flux [Wm-2] H !                                   net heat flux at water surface [Wm-2]  "#                                       surface buoyancy flux [Wkg-1] k = 0.41                             von Karman constant [dimensionless]      mE                                     evaporation rate [kg m-2 s-1] P*/E                                  ratio of effective precipitation to evaporation [dimensionless] $                                       salinity [kgm-3] $%                                      total stability [Jm-2] $%                                    salinity stability [Jm-2] $%&                                    temperature stability [Jm-2] '                                      water temperature [oC]           '(                                       mean temperature [oC] Tmd                                   temperature of maximum density [oC] V                                       total volume [m3] W                                     wind speed [ms-1] ) 	                                 wind speed measured at 10 m [ms-1] z                                       depth from the surface [m]      x     Acknowledgements   This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC). The author would also like to thank Dr. Gregory A. Lawrence, Canada Research Chair in Environmental Fluid Mechanics and Dr. Roger Pieters, from UBC department of Earth and Ocean Sciences, for their helpful comments and support of the project.   DAVOOD HASANLOO The University of British Columbia August 2014            xi    Dedication       This thesis is dedicated to my parents and my beloved wife, for their endless love, support and encouragement.        

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