Remote Sensing for Regional Assessment and Analysis of Minnesota Lake and River Water

Quality

Leif OlmansonMarvin Bauer

Patrick Brezonik

UNIVERSITY OF MINNESOTA

Areas of Research and Accomplishments

• Developed large Landsat water clarity database ~10,500 MN lakes

– Analyzed geospatial and temporal trends of water clarity in Minnesota

• Investigated and evaluated alternative remote sensing systems for regional water quality assessment

• Developed techniques for remote sensing of optically complex river waters using high spatial and spectral resolution airborne imagery

How clear is your Lake?

Lake Water Quality Monitoring: Summary

1. Citizens measure lake clarity

2. Near the same time, satellites collect imagery

4. Clarity of all lakes is classified

~1,000 Lakes monitored

Over 10,000 Lakes monitored

3. Build statistical models

y = -15.583x + 4.6742R2 = 0.84

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0.15 0.2 0.25 0.3 0.35 0.4 0.45

TM3:TM1 Ratio

ln(S

DT) -

- met

ers

0

500

1000

1500

2000

2500

3000

3500

>4 3-4 2-3 1-2 0.5-1 <0.5

Water Clarity (m)

Num

ber o

f Lak

es

Minnesota Lake ClarityLake Level 2005

33‐year “Census” of Minnesota lake clarity with 7 assessments for 1975–2008

Over 10,000 lakes classified for each time periodAll lakes >8 hectares are includedDatabase includes 1‐ 4 measurements per time period

Used for statistical analysis of Lake water clarity

Water Clarity Trends by Ecoregion, 1985 − 2005

75%

15%

10%

93%

1%6%

95%

3%2%

85%

8%7%

68%

27%

5%

80%

12%8%

76%

19%

5%

NLF4,717 lakes

RRV184 lakes

NGP534 lakes

WCBP520 lakes

NMW155 lakes

NCHF3,496 lakes

DLA41 lakes

9,647 lakes assessed in 1985, 1990, 1995, 2000 and 2005

1,039 lakes (10.8%) had trend line change ≥ 10 TSI units

440 (4.6%) improved clarity 599 (6.2%) decreased clarity

0

50

100

150

200

250

<20 20-50 50-150 150-500 >500

Num

ber

of L

akes

Lake Area (acres)

Minnesota Lakes with Trends by Size

0

50

100

150

200

250

300

Type 5 Type 4 Type 3 Type 2 No ID

Num

ber o

f Lak

es

Wetland Type from Bulletin 25

Minnesota Lakes with Trends by Type

Land cover versuswater clarity by depth

within lake watershed

August 25, 2008Imagery

MODIS Terra 500 mCalibrated Radiance

• MODIS 250, 1000 m calibrated radiance• MODIS 8-day surface reflectance

MERIS L1 TOA Calibrated Radiance 

• MERIS L2 Surface radiance/reflectance (Bright Pixel method)

• MERIS C2 Water leaving reflectance (radiative transfer simulations-NN method)

Landsat ETM+ SLC off

Comparison and Evaluation of Medium to Low Resolution Satellite Imagery for Regional Lake Water Quality Assessment

Objectives

• Develop the capability for frequent monitoring, of clarity and chlorophyll, in medium-to-large lakes using MODIS and MERIS data.

• Compare alternative sensors.

Landsat ETM+ 30mMERIS 300mMODIS 250 & 500mMODIS 1000m

Reflectance spectra of 15 Minnesota lakes with Landsat, MERIS and MODIS band locations indicated (Menken et al. 2006) 

Landsat ETM+ 30mMERIS 300mMODIS 250 & 500mMODIS 1000m

Reflectance spectra of 15 Minnesota lakes with Landsat, MERIS and MODIS band locations indicated (Menken et al. 2006) 

Image processing calibration fit and lakes assessed for Landsat, MERIS and MODIS (8/25/08)

Imagery Product N R2 N R2 Spatial  MN lakes #  Lake Size

Landsat  280 0.83 177 0.79 30 m 10,500 4 haMERIS L1 229 0.83 90 0.85 300 m 896 150 ha

MERIS  L2 140 0.77 56 0.76 300 m 471 300 ha

MERIS C2  186 0.50 75 0.41 300 m 664 250 ha

MODIS L1B 305 0.65 123 0.57 250 m 1,257 125 ha

MODIS L1B 110 0.75 42 0.79 500 m 385 400 ha

MODIS L1B 7 0.77 6 0.61 1000 m 57 1000 ha

MODIS 8‐day  110 0.75 47 0.78 500 m 385 400 ha

Imagery Product N R2 N R2 Spatial  MN lakes #  Lake Size

Landsat  280 0.83 177 0.79 30 m 10,500 4 haMERIS L1 229 0.83 90 0.85 300 m 896 150 haMERIS  L2 140 0.77 56 0.76 300 m 471 300 haMERIS C2  186 0.50 75 0.41 300 m 664 250 haMODIS L1B 305 0.65 123 0.57 250 m 1,257 125 ha

MODIS L1B 110 0.75 42 0.79 500 m 385 400 ha

MODIS L1B 7 0.77 6 0.61 1000 m 57 1000 ha

MODIS 8‐day  110 0.75 47 0.78 500 m 385 400 ha

Secchi Disk Chl a

Image processing calibration fit and lakes assessed for Landsat, MERIS and MODIS (8/25/08)

Imagery Product N R2 N R2 Spatial  MN lakes #  Lake Size

Landsat  280 0.83 177 0.79 30 m 10,500 4 haMERIS L1 229 0.83 90 0.85 300 m 896 150 ha

MERIS  L2 140 0.77 56 0.76 300 m 471 300 ha

MERIS C2  186 0.50 75 0.41 300 m 664 250 ha

MODIS L1B 305 0.65 123 0.57 250 m 1,257 125 ha

MODIS L1B 110 0.75 42 0.79 500 m 385 400 ha

MODIS L1B 7 0.77 6 0.61 1000 m 57 1000 ha

MODIS 8‐day  110 0.75 47 0.78 500 m 385 400 ha

Imagery Product N R2 N R2 Spatial  MN lakes #  Lake Size

Landsat  280 0.83 177 0.79 30 m 10,500 4 haMERIS L1 229 0.83 90 0.85 300 m 896 150 haMERIS  L2 140 0.77 56 0.76 300 m 471 300 haMERIS C2  186 0.50 75 0.41 300 m 664 250 haMODIS L1B 305 0.65 123 0.57 250 m 1,257 125 ha

MODIS L1B 110 0.75 42 0.79 500 m 385 400 ha

MODIS L1B 7 0.77 6 0.61 1000 m 57 1000 ha

MODIS 8‐day  110 0.75 47 0.78 500 m 385 400 ha

Imagery Product N R2 N R2 Spatial  MN lakes #  Lake Size

Landsat  280 0.83 177 0.79 30 m 10,500 4 haMERIS L1 229 0.83 90 0.85 300 m 896 150 haMERIS  L2 140 0.77 56 0.76 300 m 471 300 haMERIS C2  186 0.50 75 0.41 300 m 664 250 haMODIS L1B 305 0.65 123 0.57 250 m 1,257 125 ha

MODIS L1B 110 0.75 42 0.79 500 m 385 400 haMODIS L1B 7 0.77 6 0.61 1000 m 57 1000 ha

MODIS 8‐day  110 0.75 47 0.78 500 m 385 400 ha

Secchi Disk Chl a

Landsat TM 30 m MODIS 500 m

*14,528 acre lake

Lake Minnetonka* Water QualityAugust 25, 2008

MERIS water clarity MERIS chlorophyll a

Map LegendSD Chl a(m) (μg/L)

Hyperspectral Imagery for Water Quality Assessment of the Mississippi River and its

Major Tributaries in Minnesota

Mississippi River water

Minnesota River water

• Monitor the water quality of optically complex / dynamic rivers.

• Both Phytoplankton or inorganic sediment are optically dominant.

Major Minnesota Rivers

September 5, 2003 Landsat TM imagery

Mississippi River40-45% of flow

20% of TSS load

Minnesota contributes2.9% of total nitrogen flux

2.0% of total phosphorus fluxdelivered to the Gulf of Mexico

St. Croix River25-30% of flow5% of TSS load

Minnesota River25-30% of flow

75% of TSS loadSpring Lake

Discharge (cfs) August 19, 2004 August 15, 2005 August 30, 2007River Site Mean 26,604 Discharge (cfs) 9,130 Discharge (cfs) 7,370 Discharge (cfs) 8,070

Minnesota Jordan 8810 - 33% 3190 - 35% 1840 - 25% 4160 - 52%Mississippi Anoka 11700 - 44% 2770 - 30% 4100 - 56% 1930 - 24%

St. Croix Stillwater 6094 - 23% 3170 - 35% 1430 - 19% 1980 - 24%

Major Minnesota Rivers

September 5, 2003 Landsat TM imagery

Mississippi River40-45% of flow

20% of TSS load

Minnesota contributes2.9% of total nitrogen flux

2.0% of total phosphorus fluxdelivered to the Gulf of Mexico

St. Croix River25-30% of flow5% of TSS load

Minnesota River25-30% of flow

75% of TSS loadSpring Lake

Discharge (cfs) August 19, 2004 August 15, 2005 August 30, 2007River Site Mean 26,604 Discharge (cfs) 9,130 Discharge (cfs) 7,370 Discharge (cfs) 8,070

Minnesota Jordan 8810 - 33% 3190 - 35% 1840 - 25% 4160 - 52%Mississippi Anoka 11700 - 44% 2770 - 30% 4100 - 56% 1930 - 24%

St. Croix Stillwater 6094 - 23% 3170 - 35% 1430 - 19% 1980 - 24%

LN of variable Bands r2

T Tube (cm) 705 0.77–0.91Turbidity (NTU) 705 0.77–0.93

TSS (mg/L) 705 0.77–0.93VSS (mg/L) 705/670 0.80–0.94Chl a (µg/L) 705/670 or 705/620 0.75–0.93

NVSS (mg/L) 705 & 705/670 0.85–0.97a

NVSS/TSS (%) 705 & 705/620 0.73–0.91a

aR2

River Water Quality Model Development *

Characteristic Reflectance Spectra * Used most consistent (2004, 2005 and 2007) best fit band or band combination model for each water quality variable

LN of variable Bands r2

T Tube (cm) 705 0.77–0.91Turbidity (NTU) 705 0.77–0.93

TSS (mg/L) 705 0.77–0.93VSS (mg/L) 705/670 0.80–0.94Chl a (µg/L) 705/670 or 705/620 0.75–0.93

NVSS (mg/L) 705 & 705/670 0.85–0.97a

NVSS/TSS (%) 705 & 705/620 0.73–0.91a

aR2

River Water Quality Model Development *

Characteristic Reflectance Spectra * Used most consistent (2004, 2005 and 2007) best fit band or band combination model for each water quality variable

LN of variable Bands r2

T Tube (cm) 705 0.77–0.91Turbidity (NTU) 705 0.77–0.93

TSS (mg/L) 705 0.77–0.93VSS (mg/L) 705/670 0.80–0.94Chl a (µg/L) 705/670 or 705/620 0.75–0.93

NVSS (mg/L) 705 & 705/670 0.85–0.97a

NVSS/TSS (%) 705 & 705/620 0.73–0.91a

aR2

River Water Quality Model Development *

Characteristic Reflectance Spectra * Used most consistent (2004, 2005 and 2007) best fit band or band combination model for each water quality variable

Pig’s Eye Lake and the Mississippi River at St. Paul showing the transition from

inorganic sediment dominated to phytoplankton dominated

conditions, August 30, 2007.

Turbidity Chlorophyll a NVSS:TSS

Pig’s Eye Lake

Pig’s Eye Lake and the Mississippi River at St. Paul showing the transition from

inorganic sediment dominated to phytoplankton dominated

conditions, August 30, 2007.

Turbidity Chlorophyll a NVSS:TSS

Pig’s Eye Lake