Earth Observation & Inland Water Quality Monitoring

Caren Binding

Environment Canada Water Science & Technology Directorate

NetCOLOR WorkshopSaint-Hubert, Quebec, 17-18 November 2015

• Introduction to Canadian inland waters & EC water quality mandate

• EO of inland water quality

• Water Clarity: trends in the Great Lakes whiting events absorbing waters

• Algal Blooms: types & impacts effects of cell buoyancy & bloom patchiness MERIS application on Lake of the Woods Lake Winnipeg bloom indices winter diatom/summer cyanobacteria blooms on Erie

• Future Directions

Outline

Canada’s Inland WatersFresh water covers ~8 % of Canada’s surface area:

> 30,000 lakes 3-99 km2

565 lakes > 100 km2

Highly variable lake properties:

oligotrophic eutrophic turbid DOC loaded whiting events ice cover optically deep/optically shallow waters

EC’s Water Quality Obligations

• Responsibility for monitoring and management of fresh water resources is shared by the federal, provincial, and municipal governments

• EC’s Water Science & Technology Directorate - research, monitoring, and reporting on fresh water quality

• Areas of national and international interest, and transboundary waters with Federal commitments

• Current areas of focus: G. Lakes-St Lawrence, L. Winnipeg & Lake of the Woods

• The Canada Water Act (1970), Canadian Environmental Protection Act (1999), GLWQA AOC, LaMP, RAP

EO & inland water quality

EO of inland water quality often complicated by: large dynamic range in WQ constituent concentrations, highly dynamic processes, optically complex waters, bottom reflectance, land adjacency effects, complex atmosphere, suboptimal sensor spec…

Inland water quality issues of interest using EO:

• Nearshore plumes – river loadings, runoff & shore erosion

• Algal blooms – HABs, toxins, taste & odour, anoxia

• Water clarity – aesthetics, productivity, invasive species

• Submerged vegetation

• Oil slicks

Great Lakes Water Clarity

MODIS monthly Rrs551 Jan 05-Dec 07

• Great Lakes have experienced widespread changes in water clarity over the last several decades in response to invasive species, nutrient management, biogeochemical changes, changes in the watershed and climate

• Secchi disk depth often the only historical record of water clarity ~ >14,000 measures over the Great Lakes

• Rrs~550 records bright-water events such as algal blooms, suspended sediments and whiting events

• > 1300 matchups between Zsd and Rrs~550 over the three sensor periods

Great Lakes Water Clarity

• Multi-sensor analysis of satellite-derived water clarity over three decades using data from CZCS, SeaWiFS and MODIS

• Allowing spatial and temporal assessment of Zsd over the G. Lakes

• Simple empirical algorithm, based on assumption that Zsd and Rrs~550 are driven primarily by bb

Great Lakes Water Clarity

• Remarkable and complex changes in water clarity over the Great Lakes

• Lakes Ontario, Huron, and Michigan: > 50% increase in Zsd

• Lake Erie - highly variable Zsd with no consistent long term trends

• Lake Superior - fairly consistent water clarity

Binding et al. (2015) L&O

Water Clarity & Whiting Events

• Water clarity in Sept/October on Lakes Michigan and Ontario often driven by “Whiting Events”

• Precipitation of highly scattering CaCO3 resulting in bright chalky lake appearance

• Triggered by lake temperature and/or photosynthetic effects on pH

• Dramatically reduced frequency/intensity of events on Lake Michigan, attributed to reduction in dissolved calcium because of mussel uptake

• Lake Ontario – ongoing events, particularly intense in 2013/14

Dittrich & Obst, 2004

Lake Ontario August 24 2013, MODIS

Lake Michigan, August 2004, MODIS

Water clarity in absorbing waters

• Simple Zsd-Rrs relationship breaks down in strongly absorbing waters

• South basin Lake Winnipeg – black water (i.e. negligible water-leaving radiance due to strong absorption) after spring melt/loadings

• Analytical solution (Lee et al.) with contribution from both absorption and scattering more effective

Algal Blooms• Widespread concerns over increasing

occurrence and intensity of algal blooms

• Lake Winnipeg declared "Threatened Lake of the Year, 2013" by the Global Nature Fund

• Erie, 2014 - City of Toledo warned half a million residents against drinking municipal water

• Renewed binational attention on the need for urgent actions to reduce nutrient inputs and associated algal blooms

• Remote sensing playing an increasing role in detection, monitoring, and prediction of algal blooms

Algal Blooms – who are we interested in and why?

• Some cyanobacteria known to produce toxins*, others taste & odour compounds

• Impacting drinking/recreation water quality & treatment costs

• Poor aesthetics – tourism/recreation impacts• Beach fouling, avian botulism• Contributing to anoxic events fish kills and dead zones• Food web & ecosystem impacts

*Toxins are colourless. Not all strains are toxic and not all cells of toxic strains produce toxins – highly variable and poorly understood, complicating EO HAB applications.

Cyanobacteria - Microcystis, Planktothrix, Anabaena, AphanizomenonDiatoms – Aulacoseira (winter blooms)Benthic Attached Algae - Cladophora/Lyngbya

Surface Blooms, Cell Buoyancy & Patchiness• Blooms are highly dynamic in space & time

• Patchiness introducing large variability for in situ sampling & image validation

• Cell buoyancy depends on the extent to which gas vesicle synthesis counteracts carbohydrate cell ballast

• Cyano buoyancy + reduced mixing surface scums

• Visible response to wind events: repeated mixing & re-surfacing of algal cells

MERIS Application to Eutrophic Waters

Non-zero NIR L1 radiance due to algae with peak at 708 nm

Lake of the Woods:• Optically & hydrologically complex• Experiences recurring, intense cyano blooms• Chlorophyll up to 300 mg L-1 • Very high DOC (aCDOM 2-3 m-1) • Shallow, turbid waters

L1 and L2 MCI correlate strongly with surface chlorophyll

• MERIS MCI applied to LoW to monitor algal bloom occurrences

• Relating timing, intensity and areal extent of blooms to climate variables and nutrient loadings to further understand drivers of bloom conditions

• Intense blooms observed during warmer, drier years

• Wind mixing and cell buoyancy dynamic bloom conditions

MERIS Application to Eutrophic Waters

Low Bloom September 2009

Surface Blooms & Algal Heating• Intense surface algal scums - algal absorption leads to surface heating

•

• Theory supports surface heating ~4°C for Chl ~100 mg m-3

• Potential for positive feedback in cyanobacteria growth?

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Lake Winnipeg Algal Bloom Monitoring• MERIS imagery used to demonstrate operational EO

bloom monitoring capabilities

• NRT bloom detection

• Annual reporting on quantitative bloom indices; intensity, duration and areal extent

• Multi-year time series analysis

Winter Diatom Blooms on Lake Erie

• Winter blooms of Diatom Aulacoseira on Lake Erie, chlorophyll ~100 mg L-1

• L1 MCI detects blooms within and surrounding surface ice• Subtracting clean ice signal - radiance in agreement with aCHL

• Location of blooms within ice in agreement with in situ chlorophyll along cruise track

Binding et al (2011) JPR

• Chlorophyll-a present in all algae – indicator of total biomass

• Phycocyanin - indicator pigment of cyanobacteria

• Pigment absorption effects detected in reflectance

• Cyano dominance inferred by phycocyanin to chlorophyll-a ratio

• Currently being validated using in situ bloom composition (algal ID, fluorescence)

Cyanobacteria Discrimination

Future Directions

• Move towards operational delivery of established water quality products to end users

• Use satellite-derived WQ estimates to further understand lake biogeochemical processes and effects of watershed, ecosystem, and climate changes

• Preparation for inclusion of sentinel-3 into NRT image processing and delivery

• Further exploration of hyperspectral applications (particularly for algal bloom composition) in anticipation of future sensors

• Expansion of current geographic areas of interest (G. Lakes, Winnipeg, Lake of the Woods) to include additional priority watersheds with federal mandate