xing fang ph.d., p.e., d.wre, associate professor department of civil engineering

Effects of Global Climate Warming on Water Quality Characteristics and Fish Habitats in Lakes of the

Contiguous USA

Xing FangPh.D., P.E., D.WRE, Associate Professor

Department of Civil EngineeringAuburn University

Auburn, Alabama 36849, USA

Acknowledgements

• Thanks for NIER’s invitation and arrangement on attending the

international seminar.• Thanks for the support from US EPA to conduct research projects

on the topic presented here.

Presentation Outline:

• Model overview (MINLAKE96)• Database for model simulation• Impacts on water temperature characteristics• Impacts on snow and ice cover characteristics• Impacts on dissolved oxygen characteristics• Impacts on fish habitats in lakes• Conclusions

1. Model Overview - MINLAKE96• MINLAKE96 uses a mixed-layer approach to

simulate water temperature and dissolved oxygen distribution day by day. It is a one-dimensional model. It simulates water temperature and dissolved oxygen in open water season and ice cover period.

• The model can be run continuously for number of years with algorithm to model ice formation date, snow accumulation and melting, ice growth and decay, and ice melting date.

Schematic of a stratified lake with a 10 m sediment layer showing heat transfer components and water/sediment temperature

profiles in the open water season and during the ice cover period

Water Temperature Modeling p

wwz

w

cH

zTAK

zAtT

1

Dissolved Oxygen Modeling

Check one-

dimensional

assumption

using DO and

temperature

measurements

in Fish Lake

(Minnesota)

Year-round

lake model

development

and

applications

Simulated and observed water temperature profiles in winter period for Thrush Lake, MN

Simulated and observed snow and ice thickness in winter period for Thrush Lake, MN

Model PerformanceQuantitative error measurements (between measured

and simulated values in 9 lakes) of the model are

Standard errors between simulated and observed ice thickness and snow depths for three lakes (128 data points over 8 years) are 0.07 m and 0.12 m, respectively.

Nine lakes are Fish Lake, Cedar Lake, Lake George, Lake Orchard, Lake Riley, Square Lake, Thrush Lake, Lake Wabasso, and Lake Waconia with total of 5,976 data pairs.

Error Parameter Temperature (o C) DO (mg/l)

Standard error of estimate 1.43 (0.5 for winter) 1.93

R2 0.92 0.71

2. Modeling Database: Regional Lake Designation

Frequency distributions

of lake surface area,

maximum depth, and

Secchi depths for

3002 Minnesota

Lakes.

• Past climate data – 209 weather stations from 1961 to 1979 (air temperature, dew point temperature, wind speed, solar radiation, sunshine percentage, rainfall and snowfall.

• Future climate scenario – The second generation Canadian Climate Centre Global Circulation Model (3.75o x 3.75o), apply for monthly increments or ratios.

Projected air temperature increase due

to climate warming

Past (1961-1979) and projected 2xCO2 climate scenarios (monthly averages) at Duluth, MN.

3. Impacts on Snow and Ice Cover Characteristics

Parameters studied: frequency of occurrence and duration of ice cover, dates of ice-in (freeze-over) and ice-out

(melting), maximum ice and snow thickness.

Simulated earliest ice-out

date under past

(1962 – 1979) and

future (2xCO2) climate

scenario

Simulated annual cumulative days of ice cover on small, medium-

depth lakes under past

climate conditions

Projected difference of

annual cumulative days of ice cover

on small, medium-depth lakes

4. Impacts on Water Temperature Characteristics

Parameters studied: maximum and minimum surface and bottom water temperatures, .

Strongly dependent

on geographic

location

More or less independent of lake types

Regional Lake Types for Contiguous USA Study

Simulated maximum bottom water temperature under the past climate conditions

Simulated maximum temperature difference between lake surface and bottom

Simulated change or difference (GCM- Past) on seasonal stratification ratio (during open water

season) for deep medium lakes

5. Impacts on Dissolved Oxygen

Characteristics

Parameters studied: minimum surface and

hypolimnetic DO during open water

season and ice cover period, number of dates

and percent lake volume with anoxic

conditions.

Simulated average

dissolved oxygen (mg/l)

isopleths for a

shallow eutrophic lake (10

km2) near Duluth, MN under past and future

climate scenario

winter fish kill

DO criteria for three fish guilds: cold-water and cool-water fish - 3.0 mg/l; and warm-water fish - 2.5 mg/l

A schematic distribution of survival and growth of fish in a seasonally stratified lake

6. Impacts on Fish Habitats in Lakes

Guild Lower good-growth

temperatureLGGT, (oC)

Upper good-growth

temperatureUGGT, (oC)

Upper lethal temperature

LT, (oC)

Optimum temperature

OT, (oC)

Dissolved Oxygen

DO, (mg/l)

Cold-water1

Mean Range

9.0(6.4-11.8)

18.5(15.5-21.2)

23.4(22.1-26.6)

15.3(11.5-18.7)

3.0

Cool-water2

Mean Range

16.3(13.2-18.2)

28.2(27.7-28.8)

30.4(28.0-32.3)

25.1(24.0-25.7)

3.0

Warmwater3

Mean Range

19.7(17.7-22.5)

32.3(31.3-34.7)

34.5(32.3-36.0)

29.2(27.0-32.0)

2.5

Thermal and dissolved oxygen criteria for cold-, cool- and warm-water fish guilds

1Cold-water species: brook trout, brown trout, chinook salmon, chum salmon, coho salmon, mountain whitefish, pink salmon, and rainbow trout.

Simulated

depth-

time

contour

for

shallow

large

eutrophic

lake near

Duluth,

MN

Simulated

depth-

time

contour

for cool-

water fish

in

medium-

depth

medium-

size

trophic

lake

Fish Habitat Model Validation• Simulated fish habitats were compared with fish

observations in 3002 Minnesota lakes.• Simulated fish habitats agree with observations in

all medium and deep lakes, small and medium-size shallow oligotrophic lakes for cold-, cool-, and warm-water fish guilds.

• Winterkill was simulated to occur in shall eutrophic and mesotrophic lakes. Sensitivity analysis shows that a lower DO limit (<0.5 mg/l) produced better agreement with the fish observation database than higher limits.

Distribution of number of lake types

with suitable

fish habitat for cold-

water fish at 209

locations in the

contiguous USA

Distribution of number of lake types

with suitable

fish habitat for cool-

water fish at 209

locations in the

contiguous USA

Winterkill

Summerkill

Distribution of number of lake types

with suitable

fish habitat for warm-water fish

at 209 locations in

the contiguous

USA

Conclusion Remarks• Simulated water quality and ice cover characteristics were

related to lake geometric and trophic characteristics and to geographic location.

• The 2xCO2 climate scenario is projected to increase lake surface temperatures by up to 5.2oC when CCC GCM projects an increase of mean annual air temperature up to 6.7oC.

• The duration of seasonal summer stratification is projected to be up to 66 days longer under a 2xCO2 climate scenario, and this leads to longer period of anoxic hypolimnetic conditions that will result various negative environmental and ecological impacts in lakes.

Conclusion Remarks• Projected climate warming has strong impact on

ecological conditions in ice-covered lakes, e.g., later ice formation, earlier ice-out, and short ice cover period (shorten up to 90 days).

• Climate warming is projected to reduce the number of locations in the contiguous U.S. where lakes have suitable cold- and cool-water fish habitat, by up to 45% and 30%, respectively. Summerkill under the projected 2xCO2 CCC climate scenario is projected to have a significant negative influence on cold-water fish in northern lakes and cool-water fish in southern lakes of the contiguous U.S., where suitable habitat existed under historical conditions.

Thank You!

More information and journal papers about the study:

http://eng.auburn.edu/users/xzf0001/