Precipitation-Runoff and Streamflow-Routing Models for the ...

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diffusion at selected grid intervals (Jobson, 1989).Low-end values of area were primarily defined fromtime-of-travel studies, and high-end values were determinedfrom flood-study cross sections. Widths weredetermined from streamflow measurements, 1:24,000-scale topographic maps, and flood-study cross sections.Diffusion coefficients were computed fromassociated width and discharge data.Area ParameterAverage area (A) of a natural channel wasapproximated by an equation of the form (Jobson,1989):A = A 1 Q A 2 + A 0 (1)AREA (A), IN SQUARE FEET2,0001,5001,00050000 10,00020,000where,A 1 is the hydraulic area geometry coefficient,Q is the stream discharge of interest,A 2 is the hydraulic area geometry exponent, andA 0 is the area at zero flow (intercept or offset).The equation constant, exponent, and offsetdescribe the relation of area to discharge for a givenstream reach in the DAFLOW model and are listed inAppendix 1 for approximately 760 miles of streams.Figure 12 shows a typical area relation at a USGSstream-gaging-station location where area data werealso available from discharge measurements. The lowend of the relation was defined by time-of-travelmeasurements between the stream-gaging station andsome distance downstream. Data points in the middleof the relation were from discharge measurementsmade at the stream-gaging station. The highest pointon the rating was defined by a measured cross sectionfrom a flood-frequency report for a 100-year frequencyflood of estimated discharge (U.S. Army Corpsof Engineers, 1968–72).Only a few channels did not have time-of-travelinformation available for use in determining area relations.The time-of-travel data reflect the geometry andwater-storage characteristics of a reach and are a reliablemeans of estimating average low-flow geometry.For the few channels without time-of-travel measurements,streamflow measurements made at streamgagingstations and miscellaneous locations were usedto estimate the geometry. High-flow-area values camefrom flood-study cross sections, which were availablefor most channels at approximately 10-mile intervals.Intermediate values were usually interpolated on astraight-line basis. Area relation coefficients, exponents,and intercept values for all channels are listed inAppendix 1.Because equation 1 represents an average crosssectionalarea for a specific stream reach that is longcompared to its width, changes in stream geometrycaused by floods or other events are moderated. Forexample, during a flood, one part of the reach may bescoured while another part is subjected to sedimentation.The net result is little change to the averagegeometry. Dye-tracer studies to define travel timeswere made on sections of the Willamette and SantiamRivers in 1968 and in 1992. Travel times determinedfor the same magnitude of stream discharge were notsignificantly different when computed with either the1968 or 1992 data.Width ParameterA = 3.3Q 0.62 + 25DISCHARGE (Q), IN CUBIC FEET PER SECONDFigure 12. Typical area-discharge relationdeveloped from time-of-travel data, stream-gagingstationmeasurements, and flood-study crosssectiondata. (This relation is for the reach of theCalapooia River between river miles 40.4 and 45.5near the U.S. Geological Survey stream-gagingstation at Holley [14172000].)Average stream width (Wfs) of a natural channelwas also approximated by an equation (Jobson, 1989)that has the form:Wfs = W 1 Q W 2 (2)where,W 1 is the hydraulic width geometry coefficient,Q is stream discharge, andW 2 is the hydraulic width geometry exponent.32
Low-flow width was primarily scaled from1:24,000 topographic maps or higher resolution arealphotography. Both map and photographic informationwere tagged with a date of flight, and the correspondingstream discharge was obtained from USGSstreamflow records. All high-flow widths came fromflood-study cross sections. Missing data were approximatedby interpolation and extrapolation. Width-relationcoefficients and exponents for all channels are inAppendix 1.Diffusion CoefficientsValues for the diffusion coefficient (D f ) wereobtained from the channel slope (S 0 ), discharge (Q)ofinterest, and average width (equation 2) by using thefollowing equation by Doyle and others (1983):D f = Q/2S 0 W (3)Time-of-Travel StudiesDiffusion coefficients for specified high and lowflows are in Appendix 1. Slope as shown in Appendix1 was determined from either topographic maps orfrom U.S. Army Corps of Engineers (1968–72) floodplaininformation.Special Studies to Document Low FlowLow-streamflow data were needed at criticallocations to calibrate low-flow model parameters andto relate streamflow to physical properties of the basin.Time-of-travel studies using dye tracers and low-flowmeasurements to define ground-water gains and losseswere made during the study to identify model lowflowparameters and to better understand the low-flowsystem (fig. 13).Time-of-Travel StudiesIn the time-of-travel studies, rhodamine WT dyewas injected at a selected location in a stream, andGain-Loss Studies1992-93 studies(Lee, 1995)1968 studies(Harris, 1968)Figure 13. Location of time-of-travel and gain-loss studies, Willamette River Basin, Oregon.33
Page 1: Precipitation-Runoff and Streamflow
Page 4 and 5: U.S. DEPARTMENT OF THE INTERIORBRUC
Page 6 and 7: Determining Travel Time and Dilutio
Page 8 and 9: 2. Stream-gaging stations used to c
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Page 12 and 13: network-routing models where availa
Page 14 and 15: made on the main stem at base-flow
Page 16 and 17: Figure 1. Willamette River Basin, O
Page 18 and 19: EvapotranspirationINPUTSAirtemperat
Page 20 and 21: Table 1. Climate stations used to c
Page 22 and 23: Table 2. Stream-gaging stations use
Page 24 and 25: Figure 4. Mean annual precipitation
Page 26 and 27: Major Land Use MapHydrologic Soil G
Page 28 and 29: 0.5 mi 2 , created in the merge of
Page 30 and 31: Table 6. Geology and soils matrix o
Page 32 and 33: tion value of the HRU class by the
Page 34 and 35: Table 8. Selected monthly basinwide
Page 36 and 37: Figure 9. Location of Precipitation
Page 38 and 39: Table 11. Statistical analyses of P
Page 40 and 41: flow can become a significant compo
Page 44 and 45: samples were collected at various d
Page 46 and 47: 3,0002,500June 21-30, 1993September
Page 48 and 49: stream network is shown on figure 1
Page 50 and 51: 122˚30´ 15´122˚00´121˚45´Roc
Page 52 and 53: 123˚22´30´´ 123˚15´ 123˚00´
Page 54 and 55: 123˚00´´ 45´30´122˚15´45˚15
Page 56 and 57: YamhillRiver123˚45´ 30´ 15´123
Page 58 and 59: 123˚07´30´´ 123˚00´ 45´ 30´
Page 60 and 61: 123˚07´30´´ 123˚00´ 45´ 30´
Page 62 and 63: 44˚15´14166000122˚07´30´´Will
Page 64 and 65: 122˚15´ 122˚00´121˚52´30´´4
Page 66 and 67: 44˚52´30´´45´122˚15´ 122˚00
Page 68 and 69: observed flow at the Willamette Riv
Page 70 and 71: DAFLOW model, and peak amplitude is
Page 72 and 73: 20DYE CONCENTRATION, IN MICROGRAMS
Page 74 and 75: ARC-INFO and Geographic Information
Page 76 and 77: WILL.WDMData-base file(Observed pre
Page 78 and 79: WILL.WDMData-base fileSWSTATSFreque
Page 80 and 81: Jobson, H.E., 1980, Comment on A ne
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Page 84 and 85: APPENDIX 1. STREAM GEOMETRY FOR MAI
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APPENDIX 1. STREAM GEOMETRY FOR MAI
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APPENDIX 2. ARC MACRO LANGUAGE (AML
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APPENDIX 3. DEFINITIONS OF PARAMETE
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APPENDIX 3. DEFINITIONS OF PARAMETE
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APPENDIX 4. MEASUREMENTS USED TO DE
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APPENDIX 5. EXAMPLE PRECIPITATION-R
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APPENDIX 5. EXAMPLE PRECIPITATION-R
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APPENDIX 6. DIFFUSION ANALOGY FLOW
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APPENDIX 7. PROGRAMMING STEPS TO IN
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APPENDIX 8. PROGRAMMING STEPS TO DE
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150Climatemaxtempmintempprecipitati
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APPENDIX 10. DIRECTORY TREE AND DES
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APPENDIX 11. DIRECTORY TREES AND DE
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APPENDIX 11. DIRECTORY TREES AND DE
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APPENDIX 12. DIRECTORY FOR will.wdm
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APPENDIX 13. PROGRAMMING STEPS FOR
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APPENDIX 14. INPUT FILES FOR BRANCH
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