Using Duration Curves inTMDL Development &

Implementation Planning

Discussion Panelists:

Tom Stiles (Kansas Dept. of Health & Environment)Bruce Cleland (America’s Clean Water Foundation)

ASIWPCA ”States Helping States” Conference CallJuly 1, 2003

Duration CurvesConference Call OverviewConference Call Overview

Update on Kansas Applications (Tom)

Linking to Implementation (Bruce)

Extended Uses (Bruce)

Background & Basics (Tom)

Duration CurvesCall ObjectivesCall Objectives

Initiate an exchange of ideas among States

Create an awareness of efforts in this area

Approaches to work through challenges

Expand network of contacts

Highlight issues encountered

Use several examples to frame the problem

Duration CurvesBackgroundBackground

Higher flows and NPS issues

Proper "design“ storms or recurrence intervals

One of the perpetual TMDL questions ---How to address design flow conditions …

Continually looking at workable approaches

Growing interest in use of “Load Duration Curves”

Duration CurvesSome Basic ConceptsSome Basic Concepts

Seasonal Patterns

FrequencyDistributions

Annual Variation

Daily Average Flows

0.01

0.1

1

10

100

Jan-98 Mar-98 May-98 Jul-98 Sep-98

Month

Flow

(m

m)

Daily

Elk River near Tiff City, MODaily Flow PatternsUSGS Gage: 07189000

USGS Flow Data

0

1

2

3

4

5

O D M J S

Month

Flow

(m

m)

90th

75th

50th

25th

10th

Median

Elk River near Tiff City, MOSeasonal Variation --- Flow

USGS Gage: 07189000

USGS Flow Data

0

20

40

60

80

100

120

140

160

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

YearPe

ak F

low

(mm)

Annual Peak

2-yr Peak

Elk River near Tiff City, MOPeak Flow History

USGS Gage: 07189000

USGS Flow Data

2yr Peak

Duration CurvesBasics Basics ---- Flow DurationFlow Duration

Historic hydrologic record -- daily average flows[e.g. download from USGS NWIS-Web]

Based on Cumulative Frequency Distribution

Can also look at other key recurrence intervals[e.g. median flow, 2-year peak, 7Q10]

Developed with statistical software or spreadsheet[e.g. =PERCENTILE(a1:a3650,0.5) in Excel]

Duration CurvesBasics Basics ---- Flow DurationFlow Duration

Duration CurvesBasics Basics ---- Load DurationLoad Duration

Y-axis becomes water quality parameter value[e.g. load or concentration]

Again, use Cumulative Frequency Distribution

Curve determined by target concentration andflow associated with recurrence interval

X-axis position matches flow recurrence interval

Duration CurvesBasics Basics ---- Load DurationLoad Duration

Duration CurvesBasicsBasics

Targeting focus – framework to evaluate options

Moves away from single point estimate

Easier to explain – fairly simple graphic display

Method offers a number of advantages

Being evaluated as a tool in more & more States

Context for looking at monitoring / modeling data

Duration CurvesAdvantagesAdvantages

- Targeted Programs

Help guide implementation

- Targeted Areas

- Targeted Activities

- Targeted Participants

Context to interpret monitoring & modeling data

Duration CurvesLatest Kansas ApplicationsLatest Kansas Applications

Significant Loss of Water and Chloride Load into Freshwater Aquifer

Hutchinson - Upstream Site, Salt Plants

Maize - Downstream Site, Historic Loss of Flow at Lower Flows

Arkansas River Chlorides

TMDL to set Cap on Upstream Load to Reduce Load Lost to Aquifer

No Significant Difference in Chlorides

Load Duration CurvesArkansas River ChloridesArkansas River Chlorides

10

100

1000

10000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Pct of Days Load Exceeded

Hutch (600 ppm) Maize (560 ppm)

Ark River Chloride LoadsBetween Hutch and Maize

Duration CurvesLatest Kansas ApplicationsLatest Kansas Applications

Spring River Zinc

Observed Loads Exceed Accumulated Sum of Loads at Higher Flows

Historic Mining Area in Tri-State Region

Baxter Springs Represents the Total Contribution from Drainage

Hints at Deposition of Load at Lower Flows, Resuspension of Zinc Load at Higher Flows

In-Stream Impoundment Located above Baxter Springs on the River; Silt Trap

Accumulations from Upstream Tribs Greater Than Observed Zinc Loads at Lower Flows

Load Duration CurvesSpring River ZincSpring River Zinc

Z i n c L o a d a t B a x t e r S p r i n g s

0 .1

1 .0

10 .0

100 .0

0 1 0 20 3 0 40 5 0 6 0 7 0 8 0 90 1 0 0

P c t o f t i m e l o a d e x c e e d e d

Load

in T

ons

per

Day

O b s e r v e d A c c u m u l a t e d S u m

Duration CurvesExtended UsesExtended Uses

Support watershed planning by …

Enhanced description of water quality concerns

Improved basic understanding of key processes

Focus on solution development

Duration CurvesEnhanced AssessmentEnhanced Assessment

Load Duration CurvesEnhanced AssessmentEnhanced Assessment

Connect WQ concerns to potential solutions …

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

0 10 20 30 40 50 60 70 80 90 100

Percent of Time > Load (y)

E.Co

li (#

/day

)

TargetMedian

E.Coli

Pipe Creek below ElftonSample Load Duration Curve

Median

DroughtFlood

TARGETED Participants: Point Sources

Watershed Condition -- Hydrologic

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

0 10 20 30 40 50 60 70 80 90 100

Percent of Time > Load (y)

E.Co

li (#

/day

)Target

MedianE.Coli

Willow Creek near Turkey GapSample Load Duration Curve

Median

DroughtFlood

TARGETED Programs: Riparian Buffers (e.g. CRP, CREP)

Load Duration CurvesEnhanced AssessmentEnhanced Assessment

Connect WQ concerns to potential solutions …Contributing Areas

0

0

0

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100

Percent of Time > Load (y)

TSS (lb

s/ac

re/d

ay)

Target

TSS

Chicken Run above Mt. PleasantSample Yield Duration Curve

DroughtFlood

TARGETED Activities: Contour Strips, Conservation Tillage

0

0

0

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100

Percent of Time > Load (y)

TSS (lb

s/ac

re/d

ay)

Target

TSS

Rock Creek near Moose JunctionSample Yield Duration Curve

DroughtFlood

TARGETED Areas: Streambank Erosion, Bank Stability

Duration CurvesEnhanced AssessmentEnhanced Assessment

Other potential opportunities …

Linkage to other analytical methods(e.g. models, Bacteria Source Tracking)

Provides view beyond “Status & Trends”

Expanded watershed characterization

Use with volunteer monitoring efforts

Duration CurvesBeyond “Status & Trends”Beyond “Status & Trends”

At first glance, a large gap …

1

10

100

1000

10000

Jan-67 Jan-77 Jan-87 Jan-97

Month

TSS

(mg/

L)

ObsWQS (Upper)

WQS (CWF)

Conodoguinet Creek near HogestownTime Series

Site ID: 01570000

USGS Water Quality Data

Duration CurvesBeyond “Status & Trends”Beyond “Status & Trends”

LDCs put focus on continuum of flows …

Duration CurvesExpanded CharacterizationExpanded Characterization

Importance of watershed size …Smaller ==> flashier at high flows; drier at low flows

Duration CurvesExpanded CharacterizationExpanded Characterization

Importance of wetlands & lakes …

Duration CurvesUse with Volunteer Monitoring DataUse with Volunteer Monitoring DataReference watershed

Duration CurvesUse with Volunteer Monitoring DataUse with Volunteer Monitoring DataProvides feedback opportunities …

Duration CurvesComparing WQ Data to Model OutputComparing WQ Data to Model Output

Duration CurvesComparing WQ Data to Model OutputComparing WQ Data to Model Output

Duration CurvesLook at Bacteria Source Tracking DataLook at Bacteria Source Tracking Data

Load Duration CurvesLinking to Implementation EffortsLinking to Implementation Efforts

Focus: Source Areas & Delivery Mechanisms

Source Area High Moist Mid-Range Dry Low

Point source M HSeptic systems M HRiparian areas H H MStormwater: Impervious H H HCSO's H H MStormwater: Upland H H M

EXAMPLE Duration Curve Zone

Potential for source area contribution under given hydrologic condition

Load Duration CurvesLinking to Implementation EffortsLinking to Implementation Efforts

Focus: Potential Management Practices

Source Area High Moist Mid-Range Dry Low

Point source controls L L M H HSeptic system inspection L M H H MCSO repair / abatement H H HSSO repair / abatement M H HRiparian buffers H H HPasture management H H MPet waste education & ordinances M H HHobby farm livestock education & ordinances

H H M

EXAMPLE Duration Curve Zone

Potential for effective load reductions under given hydrologic condition

Load Duration CurvesLinking to Implementation EffortsLinking to Implementation Efforts

Example: Agricultural Erosion Control

Focus: Source Areas & Delivery Mechanisms

Agricultural Fields (e.g. residue management, contour cropping)

Filter Strips

Bank Stabilization (e.g. channel stabilization, bank protection)

Gully Stabilization (e.g. grade stabilization, grassed waterways)

Duration CurvesLinking to Implementation EffortsLinking to Implementation EffortsExample: Agricultural erosion control …

Duration CurvesVirginia & Bacteria TMDLsVirginia & Bacteria TMDLs

Duration CurvesVirginia & Bacteria TMDLsVirginia & Bacteria TMDLs

Connecting the PiecesCombined Sewer OverflowsCombined Sewer Overflows

Targeted Activities

Calculation

SWMM Modeling

Treatment Basins

Tunnels

Storage Basins

Separation

Connecting the PiecesCSOs CSOs –– One ApproachOne Approach

TMDL SummaryCrooked RiverCrooked River

Components plus Opportunities

High Moist Mid-Range Dry Low

Reduction 92% 90% 79% 41% 0%

TMDL 1.39E+14 5.09E+13 2.37E+13 1.15E+13 5.09E+12Load Allocations 9.32E+12 2.73E+12 2.26E+13 1.05E+13 4.22E+12Wasteload Allocations 4.68E+11 4.68E+11 4.68E+11 4.68E+11 4.68E+11

CSO 1.25E+14 4.58E+13 0.00E+00 0.00E+00 0.00E+00Margin of Safety 4.11E+12 1.89E+12 6.20E+11 4.99E+11 4.06E+11

ImplementationOpportunities

TMDL SUMMARY Loads expressed as (cfu/day)

Stormwater Mgt.

Long Term CSO Plan Municipal NPDESRiparian ProtectionPet Waste Ordinance

Load Duration CurvesContactsContacts

Bruce Cleland America’s Clean Water Foundation(206) 463-2596 b.cleland@acwf.org

Tom Stiles Kansas Dept. of Health & Environment(785) 296-6170 tstiles@kdhe.state.ks.us