Update of Tributary Concentration and

Loading Estimates to Lake Champlain

Maurie Clark, Annie Procaccini, and Jamie Van Clief

We had a tool, not a problem● Weighted regression on time, discharge, and

season (WRTDS) model● Exploration and Graphics for RivEr Trends

(EGRET) package in R Studio coding statistical program

Learning experience...

● Phosphorus Loadingo Eutrophic conditions exist in the lake including,

South Lake, St. Albans Bay, and Missisquoi Bay segments

● TMDLo 2002 loading estimates turned down by EPA

● Outdated models… revisit your tools (Philip Halterman)

Background… we found a problem

Tributaries of interest

TributaryTotal Phosphorus

Mean Load 1000kg/yr

Mean Concentration mg/l

Winooski 152.7 .077

Missisquoi 113.6 .074

Lamoille 141.7 .099

● Using the new statistical software to evaluate phosphorus trends in and among seasons

● their causationo aided by Geographical Information

Systems (GIS)● make future recommendations

Overall Goals, How we used the model

● EGRET package-Exploration and Graphics for RivEr Trends

● WRTDS- weighted regressions on time, discharge and season.o True condition estimate

understand history of nutrientso Flow normalized estimate

evaluate loading/management process less related to river flow

R Studio

● 20 years of data● 200 samples at each

sampling siteo 100 samples needed for

estimations● Complete record of

daily discharge

Characteristics needed for analysis

Patuxent River, Maryland (Hirsch et al. 2010)

Why the need for these models?T

P

Winooski River, Vermont (Us 2015)

WRTDS Model- 1st Approach: “True Condition Estimates”

Unsampled dayst0, Q0, unknown C0

Sampled daysti, Qi, unknown Ci

How to estimate a concentration?(C0)

To: estimate the expected value of concentration for any given date (t0) and discharge (Q0)

WRTDS Model- 1st Approach: “True Condition Estimates”

Unsampled dayst0, Q0, unknown C0

Sampled daysti, Qi, unknown Ci

Sift through and give weight to the sampled days data How to estimate a concentration?(C0)

Store in the weighted regression

Run regression. Get this equation, use with t0 and Q0

Unsampled dayst0, Q0, unknown C0

Sampled daysti, Qi, unknown Ci

Sift through and give weight to the sampled days data How to estimate a concentration?(C0)

Store in the weighted regression

Run regression. Get this equation, use with t0 and Q0

Flux0 = C0 x Q0

ln(c)=β₀+ β₁ᵗ+ β₂ln(Q)+ β₃sin(2πt) +β₄cos(2πt) +ɛ

WRTDS Model- 1st Approach: “True Condition Estimates”

WRTDS- 2nd Approach: “Flow-normalized estimates”

To: estimate concentration and flux in a manner that removes variation that arises from stochasticity in discharge

WRTDS- 2nd Approach: “Flow-normalized estimates”

Discharge: viewed on any given day as a random sample of the discharges that may have happened on that day

For April 21st, 2015P(Q04/21/2015) =P(Q04/21/2014) =P(Q04/21/2013) =P(Q…) =P(Q04/21/1972)

To: estimate concentration and flux in a manner that removes variation that arise from stochasticity in discharge

WRTDS- 2nd Approach: “Flow-normalized estimates”

To compute FN C0 for April 21st, 2015 with a 31-year record of discharge:

To compute FN C0 for April 21st, 2015 with a 31-year record of discharge:

Method estimates 31 values of concentration using WRTDS modelUses the T0 but Q04/21/2015, Q04/21/2014, Q.... 04/21/1972

Take the average of the 31 estimated concentration or flux values

Flow-normalized concentration/flux

Flow-normalized concentration

Drainage area: 850 square miles 686 square miles1,044 square miles

Annual Flow Normalized Graphs of the Missisquoi, Lamoille and Winooski Rivers

Land Cover Assessment

● 2001 Lake Champlain Basin Simplified Land Cover Dataseto Developed for accurate mapping

of land uses, which influence phosphorus loading

o 19 NLCD classes -> 8 classeso Derived: National Land Cover

Dataset (NLCD) and 2001 imagery

o 30m pixel cellso Overall 88% accuracy

assessment

● Overlaid by watershed and stream corridor datao HUC - 8 watershedso 800m riparian buffer

● Statistics Derived using ArcGIS

Watershed Land Cover

Stream Buffer Land Cover

● 2009 Digital Elevation Model (DEM)o 10m cell size National Elevation Dataset

● ArcGIS Processingo Generate a slope raster, which displays terrain

steepness within the stream corridorso Assess the slope distribution using 3D analyst

5 slope classes by 15° increments

Stream CorridorGradient Assessment

Missisquoi River

Lamoille River

Winooski River

Seasonality

Conclusions

● This model supports prioritizing management practices to specific tributaries and seasons

● Flow Normalization is an applicable tool● Revisiting WQS and TMDLs● Ecological timing