Pollutant Loading from Airshed & Pollutant Loading from Airshed & Watershed Sources to Lake Tahoe: Watershed Sources to Lake Tahoe: Influence on Declining Lake ClarityInfluence on Declining Lake Clarity

John E. Reuter - University of California, Davis

Presentation TopicsPresentation Topics Lake Tahoe and overview Lake Tahoe and overview

of impactsof impacts

Transport of toxics to lakeTransport of toxics to lake

Atmospheric deposition, Atmospheric deposition, nutrient budget & nutrient nutrient budget & nutrient limitationlimitation

Current research on Current research on nutrient and particle nutrient and particle sourcessources

Linkage to Tahoe TMDLLinkage to Tahoe TMDL

Introduction to Lake Tahoe and Introduction to Lake Tahoe and

Key Environmental ImpactsKey Environmental Impacts

Air Pollution - Just One of Multiple Air Pollution - Just One of Multiple Ecosystem StressorsEcosystem Stressors

Features of Lake TahoeFeatures of Lake Tahoe

• Subalpine, oligotrophic, low nutrients in soils

• 800 km^2 drainage

• 500 km^2 lake surface

• 499 m max. depth

• 650 yr hydraulic residence

• 80% land managed by USFS

• Urban-wildland interface

Lake Tahoe: A Changing EcosystemLake Tahoe: A Changing Ecosystem

Significant portions are urbanizedSignificant portions are urbanized Increased resident populationIncreased resident population Millions of touristsMillions of tourists Peak VMT >1,000,000 miles/dayPeak VMT >1,000,000 miles/day Loss of wetland and runoff infiltrationLoss of wetland and runoff infiltration Extensive road networkExtensive road network Land disturbance - soil erosionLand disturbance - soil erosion Air pollutionAir pollution

Changing Landscape has Lead to Changing Landscape has Lead to Following Lake IssuesFollowing Lake Issues

Loss in transparencyLoss in transparency Increased algal growthIncreased algal growth Changes in biodiversityChanges in biodiversity Higher load of nutrients and fine-sedimentHigher load of nutrients and fine-sediment Wetland/riparian habitat lossWetland/riparian habitat loss Invasion of non-native biotaInvasion of non-native biota Air quality impactsAir quality impacts Appearance of toxics (e.g. PCB, Hg, MTBE)Appearance of toxics (e.g. PCB, Hg, MTBE) Significant effort on part of state and federal agencies, local

government, universities and environmental consultants to address these and other issues

Transport of Toxics to Lake Transport of Toxics to Lake and Incorporation into Biotaand Incorporation into Biota

Air Pollution is Just Not a Local Issue

Regional Transport of MercuryRegional Transport of MercuryAlan C. Heyvaert et al. (2000)

Transport of Organic ToxicsTransport of Organic Toxics

Air, water, snow & fish Air, water, snow & fish samples taken at Tahoe samples taken at Tahoe and nearby lake showed and nearby lake showed measurable levels of measurable levels of PCBsPCBs

Low levels of Low levels of contamination but mass contamination but mass balance suggests:balance suggests:

a) atmospheric sources a) atmospheric sources dominatedominate

b) out-of-basin transportb) out-of-basin transport

S. Datta, F. Matsumura et al. (1998)

Atmospheric Deposition, Atmospheric Deposition, Nutrient Budget & Nutrient Nutrient Budget & Nutrient

LimitationLimitation

Influence on Long-term Decline ofLake Clarity

Unraveling Cause(s) for Unraveling Cause(s) for Declining Water ClarityDeclining Water Clarity

• NutrientsNutrients stimulate algae stimulate algae• Fine-sedimentsFine-sediments directly directly

reduces clarity (1-20 µm)reduces clarity (1-20 µm)• Progressive accumulation Progressive accumulation

leads to long-term declineleads to long-term decline• Management strategy - P, Management strategy - P,

N, sediment controlN, sediment control• Evidence for possible Evidence for possible

recoveryrecovery• TMDL, EIP & other plans TMDL, EIP & other plans

are addressing load are addressing load reductionreduction

““Initial” Lake Tahoe Nutrient BudgetInitial” Lake Tahoe Nutrient Budget

Strongly suggests importance of AD for nutrientsStrongly suggests importance of AD for nutrients Little data on inorganic particle deposition (soils)Little data on inorganic particle deposition (soils) Size and low nutrient condition of Tahoe increases its importanceSize and low nutrient condition of Tahoe increases its importance More work underway to improve initial estimate (ARB, DRI, UCD)More work underway to improve initial estimate (ARB, DRI, UCD)

Total-N Total-P Atmospheric Deposition 234 (59%) 12.4 (28%)

Stream loading 82 (20%) 13.3 (31%)Direct runoff 23 (6%) 12.3 (28%)Groundwater 60 (15%) 4 (9%)Shore erosion 1 (<1%) 1.6 (4%)

Total 400 43.6

Jassby et al. (1994), Reuter et al. (2000)

Change in Algal Response to NutrientsChange in Algal Response to Nutrients

Long-term shift from N&P Long-term shift from N&P co-limitation to consistent P co-limitation to consistent P limitationlimitation

Data strongly suggests that Data strongly suggests that AD, with high N:P ratio is AD, with high N:P ratio is associated with this shiftassociated with this shift

Fundamental change in lake Fundamental change in lake ecosystem functionecosystem function

AD-N very important in AD-N very important in coastal oceanscoastal oceans

Another example of airshed-Another example of airshed-watershed interactionwatershed interaction

Goldman et al. (1993), Jassby et al. (1994)

Current Research on Nutrient Current Research on Nutrient and Particle Sourcesand Particle Sources

‘Not So Elementary My Dear Watson’

Current Research is a Work in ProgressCurrent Research is a Work in Progress

Sources of N, P and fine-sediment - local, regional and Sources of N, P and fine-sediment - local, regional and globalglobal

In-basin or out-of-basin: a key management questionIn-basin or out-of-basin: a key management question The Lake Tahoe Air Quality Research Scoping Document The Lake Tahoe Air Quality Research Scoping Document

(Cliff et al. 2000) identified need to look at:(Cliff et al. 2000) identified need to look at:• Fires (controlled/wild)Fires (controlled/wild)• Road dustRoad dust• Vehicle exhaustVehicle exhaust• Residential heatingResidential heating• Upwind emissionsUpwind emissions

LTADS -> CARB and universities are addressing sourceLTADS -> CARB and universities are addressing source

LTAM Predicts Smoke PM2.5 forLTAM Predicts Smoke PM2.5 forWildfire & Prescribed Burns Wildfire & Prescribed Burns

PM2.5 (µg/m3) based on 3 PM2.5 (µg/m3) based on 3 fire scenarios:fire scenarios:

a) Historical wildfire (12-16 ha)a) Historical wildfire (12-16 ha)b) Hypothetical prescribed b) Hypothetical prescribed

burn, 50-ha, Ward Valleyburn, 50-ha, Ward Valleyc) Same as b, with 100-ha c) Same as b, with 100-ha

prescribed burnprescribed burn

Significant implications for Significant implications for visibility and source for direct visibility and source for direct depositiondeposition

S. Cliff & T. Cahill (2002)

Aircraft Measurements of N & P in Forest Aircraft Measurements of N & P in Forest Fire Smoke in and Around Tahoe BasinFire Smoke in and Around Tahoe Basin

TN - 5-6 x higher in forest fire smoke than clean Tahoe air, with a TN - 5-6 x higher in forest fire smoke than clean Tahoe air, with a greater contribution by ONgreater contribution by ON

P - 10 x higher in smoke plume; much less P in slightly smokey airP - 10 x higher in smoke plume; much less P in slightly smokey air Bulk deposition measured at Tahoe 5-10 times during smoke periodBulk deposition measured at Tahoe 5-10 times during smoke period Smoke can be nutrient source, but depends on transport and depositionSmoke can be nutrient source, but depends on transport and deposition

Q. Zhang et al. (2002)

Top of bar = Particulate NBottom of bar = Gaseous N

Aerosols at South Lake Tahoe:Aerosols at South Lake Tahoe:Evidence for the Role of Road DustEvidence for the Role of Road Dust

Continuous monitoring of 8 size modes (0.09-35 µm) in summer and winter Continuous monitoring of 8 size modes (0.09-35 µm) in summer and winter with Drum Sampler at site downwind of Highway 50. Analysis for 32 with Drum Sampler at site downwind of Highway 50. Analysis for 32 elements done at 3 hr intervals.elements done at 3 hr intervals.

Conclusions:Conclusions:• Hwy 50 major source of coarse particles (2.5-35 µm)• Particles >PM10 contain most P• Previous AQ studies did not focus on larger cuts• Hwy 50 also source of fine particles (0.09-0.26 µm) from

diesels, smoking cars and fine ground road soil• Transport out over lake occurs each night• Data suggest that winter P is strong associated with road

sanding/drying conditions while in summer values are more consistent day-to-day suggesting road dust from highway and near-highway soils• Contribution to whole-lake P budget now being evaluated

Cahill et al. (2003)

Linkage to Tahoe TMDLLinkage to Tahoe TMDL

Total Daily Maximum LoadBest Understood as Water Clarity

Restoration Plan

Elements of a TMDLElements of a TMDL

Problem Statement Numeric Target Source Analysis Linkage Analysis Load Allocations Margin of Safety Implementation Plan

0 10 20 30 40 50 60 70 80 90 100

0102030405060708090

100

0 10 20 3040 50 60 70 80 90100% Nitrogen Reduction

% Phosphorus Reduction

% S

edim

ent R

educ

tion

20- 25………Red25.5-28…….Yellow28.5-32.5…..Blue33 & above..Purple

Final Secchi Depth (m)

Conceptual Load Reduction Model

Parameters are for illusrative purposes only

• Informed byClarity model

• Multiple potential solutions

Load Reduction Matrix

Effectiveness Cost Contstraints Etc.

Estimated Load

Reduction

U-1 Infiltration 4 $ 2 tbd xx kg/yrU-2 Wetland Treatment 7 $$ 7 tbd xx kg/yrU-3 Source Control 6 $ 1 tbd xx kg/yrU-4 Chemical Enhancement 9 $$$ 8 tbd xx kg/yr

A-1 Vehicle Emission Control 4 $$ 4 tbd xx kg/yrA-2 Wood Stove Management 5 $$ 3 tbd xx kg/yrA-3 Out-of-Basin Source Control 2 $$$ 9 tbd xx kg/yrA-4 Dust Management 7 $ 2 tbd xx kg/yr

ST-1 Stream Restoration 7 $$$ 5 tbd xx kg/yrST-2 Bank Stabilization 7 $$ 3 tbd xx kg/yrST-3 Hydrological Controls 5 $ 2 tbd xx kg/yr

GW-1 Fertilizer Management 3 $$ 7 tbd xx kg/yrGW-2 Source Control 8 $ 2 tbd xx kg/yr

FA-1 Road Management 6 $$$ 6 tbd xx kg/yrFA-2 Trail Management 5 $$ 5 tbd xx kg/yrFA-3 Fire Restoration 7 $$ 4 tbd xx kg/yr

xx kg/yr

FORESTED AREAS

Total Possible Load Reduction

Load Reduction Opportunities

ATMOSPHERIC

STREAM CHANNELS

GROUND WATER

URBAN

A

Urban (34%): U-2, U-6, U-14, U-26, U-56, U-78Atmospheric (12 %): A-3, A-7, A19, A43

Stream Channels (20%): ST-10, ST-34, ST-43Ground Water (12%): GW-2, GW-4, GW-18Forested Areas (22%): FA-11, FA-23, FA-25

TOTAL REDUCTION = 15,000 kg tbd/yr

B

Urban (20%)Atmospheric (25%)

Stream Channels (25%)Ground Water (15%)Forested Areas (15%)

TOTAL REDUCTION =15,000 kg tbd/yr

C

Urban (20%)Atmospheric (15%)

Stream Channels (30%)Ground Water (25%)Forested Area (15%)

TOTAL REDUCTION =15,000 kg tbd/yr

Parameters are for illustrative purposes only

Example Load Reduction Alternatives

ConclusionConclusion

Science-Based Decision MakingStakeholder Driven