Interpretation of Interpretation of Flow at Un-gaged Flow at Un-gaged Stations Stations May 1, 2007 May 1, 2007 CE 394K.2 Hydrology CE 394K.2 Hydrology Semester Project Semester Project Spring 2007 - Dr. Maidment Spring 2007 - Dr. Maidment Submitted by: Stephanie L. Johnson Submitted by: Stephanie L. Johnson
Interpretation of Flow at Un-gaged Stations May 1, 2007 CE 394K.2 Hydrology Semester Project Spring 2007 - Dr. Maidment. Submitted by: Stephanie L. Johnson. Outline. “The Big Picture” What do we have? What do we want? Methods to get what we want Assessment of one method Conclusion - PowerPoint PPT Presentation
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Interpretation of Flow Interpretation of Flow at Un-gaged Stationsat Un-gaged Stations
May 1, 2007May 1, 2007
CE 394K.2 HydrologyCE 394K.2 HydrologySemester ProjectSemester Project
Spring 2007 - Dr. MaidmentSpring 2007 - Dr. Maidment
Submitted by: Stephanie L. JohnsonSubmitted by: Stephanie L. Johnson
OutlineOutline
““The Big Picture”The Big Picture” What do we have?What do we have? What do we want?What do we want? Methods to get what we wantMethods to get what we want Assessment of one methodAssessment of one method ConclusionConclusion ““Side project”Side project”
““The Big Picture”The Big Picture”
Tres Palacios Bay
Matagorda Bay
/0 10 205 Miles
Tres Palacios BayPalacios, Texas
Data Collection in the Data Collection in the WatershedsWatersheds
Have USGS Have USGS flow dataflow data at 15-minute at 15-minute intervals for intervals for continuouscontinuous time periods time periods
Have Have random water qualityrandom water quality information at SWQM stationsinformation at SWQM stations SometimesSometimes this includes this includes flowflow (not very (not very
often)often) Copano Bay watershed:Copano Bay watershed:
7 SWQM stations with 32 years of data7 SWQM stations with 32 years of data 1900 total sampling events1900 total sampling events Flow recorded at 182 (Flow recorded at 182 (<10%<10%) of those events) of those events
Load Duration CurveLoad Duration Curve Derived from a flow duration curveDerived from a flow duration curve
Basically a cumulative frequency distributionBasically a cumulative frequency distribution Load = flow x concentration x conversion factorLoad = flow x concentration x conversion factor Calculate regulatory curve (flow x max Calculate regulatory curve (flow x max
concentration)concentration) Add monitoring data as pointsAdd monitoring data as points
Position tells if it’s in compliancePosition tells if it’s in compliance
E. Coli Load Duration Curve
1.0E+07
1.0E+08
1.0E+09
1.0E+10
1.0E+11
1.0E+12
1.0E+13
1.0E+14
1.0E+15
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Percent Exceedance
Lo
ad
(#/
da
y)
Target SS Load Target Mean Load Data
ChallengeChallenge
Need Need flow and water qualityflow and water quality information at the information at the same sitesame site In some cases this is already doneIn some cases this is already done In others we need to estimate flowsIn others we need to estimate flows
HowHow to estimate it? to estimate it? ModelModel with rainfall-runoff model or with rainfall-runoff model or
regression equations from historic dataregression equations from historic data EstimateEstimate from gaged stations from gaged stations
Previous StudiesPrevious Studies Wurbs and Sisson, 1999 (TA&MU)Wurbs and Sisson, 1999 (TA&MU)
Performed to analyze options for use in Water Rights Performed to analyze options for use in Water Rights Analysis Package (WRAP) model Analysis Package (WRAP) model
Explored: rainfall-runoff modeling, regression Explored: rainfall-runoff modeling, regression equations, and estimating from gaged stations from equations, and estimating from gaged stations from historic datahistoric data
Recommended estimatingRecommended estimating from gaged stations from gaged stations
NRCS Curve Number Adaptation MethodNRCS Curve Number Adaptation Method
Drainage Area Ratio MethodDrainage Area Ratio Method
Recommend using Recommend using N values equal to 1.0N values equal to 1.0
321 N
gaged
ungagedN
gaged
ungagedN
gaged
ungaged
M
M
CN
CN
A
AC
1N
gaged
ungaged
A
AC
gagedungaged QCQ *
Now Used Widely
Previous Studies (Cont.)Previous Studies (Cont.)
Asquith et. al, 2006Asquith et. al, 2006 Follow-up on Wurbs studyFollow-up on Wurbs study Explores N1 (Φ) valueExplores N1 (Φ) value in the Drainage Area in the Drainage Area
Important to admit your failures …Important to admit your failures … Method Method not accuratenot accurate for stations with ephemeral flows for stations with ephemeral flows Potential that Potential that highly dynamic weather conditionshighly dynamic weather conditions on on
the coast make the Drainage Area Ratio Method the coast make the Drainage Area Ratio Method less less accurateaccurate
Asquith Asquith Φ values more accurateΦ values more accurate than Wurbs’ than Wurbs’ suggestion of N1=1.0suggestion of N1=1.0
Use Asquith flow regime specific Φ values to Use Asquith flow regime specific Φ values to calculate flows at un-gaged stationscalculate flows at un-gaged stations
But……
Flow Duration Curve
SWQM Station 12948 (9/23/1968 to Present)
0.01
0.1
1
10
100
1000
10000
100000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Probability of Exceedance
Flo
w (
cfs)
Flow Duration Curve
SWQM Station 12930 (10/9/1968 to 11/5/1972)
0.01
0.1
1
10
100
1000
10000
100000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Probability of Exceedance
Flo
w (
cfs)
Flow Duration Curve
SWQM Station 12943 (10/30/1975 to Present)
0.01
0.1
1
10
100
1000
10000
100000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Probability of Exceedance
Flo
w (
cfs)
Flow Duration Curve
SWQM Station 12932 (12/18/1972 to 8/28/2002)
0.01
0.1
1
10
100
1000
10000
100000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Probability of Exceedance
Flo
w (
cfs)
Flow Duration Curve
SWQM Station 17592 (2/18/1998 to 4/9/2002)
0.1
1
10
100
1000
10000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Probability of Exceedance
Flo
w (
cfs)
ReferencesReferences
Asquith, W. H., Roussel, M.C., and Vrabel, J. 2006. Statewide Analysis of the Drainage-Area Method for 34-Streamflow Percentile Ranges in Texas. US Geological Survey Scientific Investigations Report 2006-____.
Wurbs, R., and Sisson, E. 1999. Comparative Evaluation of Methods for Distributing Naturalized Streamflows from Gaged to Ungaged Sites. Texas Water Resources Institute Technical Report No. 179.
Questions?Questions?
Weather StationsWeather StationsNational Climatic Data Center (www.ncdc.noaa.gov)National Climatic Data Center (www.ncdc.noaa.gov)
Where: Q0 = Average daily flow at the USGS gage station on the day to be forecast (cfs)Q-n = Average daily flow at the USGS gage station n days before the day modeled
(cfs)P0 = Total precipitation at the weather station on the day to be forecast (inches)
P-n = Total precipitation at the weather station n days before the day modeled (cfs)
an = Calculated constant
Beeville 5 NE vs. USGS Station Beeville 5 NE vs. USGS Station 0818970008189700