1. StreamStats Web Application streamstats.usgs.gov
Audrey Ishii, P.E.
Illinois Water Science Center

2. Overview—Streamflow Statistics
What—Estimate of streamflow under some condition, such as the 100-year flood flow, flow durations, etc.
Used in engineering design flows for bridges, culverts, mapping floodplains, setting water allocations, determining allowable waste discharges.
How Computed—
At stream gages--statistical analysis of historic flows, the flood-frequency or flow duration curve
Ungaged sites: Regression equations relating the characteristics of the curve to basin characteristics.
Q100 = a(TDA)b(MCS)c(PermAvg)d(Rf)

3. Streamflow gaging stations are not distributed evenly.
The density impacts the quality of regional analyses.
Selected discharge gages with more than 25 years of record for analysis.

4. Percentage changes in the 100-year peak flow estimate between 1987 and 2004
Max. = 35
Avg. = 6
Max. = 50
Avg. = 27
Max. = 29
Avg. = 4
Max. = 81
Avg. = 9
Max. = 24
Avg. = 7
Max. = 95
Avg. = 15
Max. = - 2
Avg. = - 8

5. Traditional Methods for Measuring Basin Characteristics
Very labor intensive and costly
Not completely reproducible
Error-prone
Often not documented well in reports
Users need source materials and expertise
Some BC not easily reproduced by GIS methods

6. GIS Methods for Basin Characteristics
Several custom software packages developed,
GIS Weasel, BasinSoft, BASINS, WMS, mostly developed for watershed modeling, often ESRI.
Needed GIS datasets not always readily available
No documented national standard methods
Several methods used for some characteristics
Users need source data and expertise
Often not documented well in reports
Some measurements are scale-dependent

7. StreamStats GIS computations
Create hydro networks of rivers and streams
Process DEM and stream network for watershed analysis
Delineate drainage basins and measure basin characteristics
Represent channel shape using three-dimensional models
Connect geospatial features to time series measurements recorded at gaging sites
Runs within ESRI Arc 8/9 software
Public domain utilities developed jointly by U. Texas at Austin and ESRI

8. StreamStats Web Application
Provides published streamflow statistics and basin characteristics for gages
Computes basin characteristics for ungaged sites
Provides regression-based estimates of streamflow statistics for ungaged sites
User Interface
ArcIMS
Streamflow Statistics Database
NSS Calculation Program
GIS Database
ArcHydro
At a
streamgage
At an ungaged location

12. Application Examples
Engineering Design—Bridges, culverts, flood-plain management
Water and Land Management—Water rights adjudication, in-stream flows, fish passage/habitat studies
Water Quality Regulation—Low flows, perennial vs. intermittent streams (TMDL’s, NPDES Permits)
Sampling Network Design—Cover a range of desired flows

13. Variation in Slope with Drainage Area

14. StreamStats Benefits
Cost—Time to delineate and compute basin characteristics reduced from hours to minutes
Accuracy—As good or better than manual methods
Consistency—Important for statistical validity
Accessibility—User does not need GIS expertise or software

16. National StreamStats Status
15 states up and running
National gages web site
18 additional states underway
Data upgrades on 3 states (PA, ID, WA)
Each state is developed (and funded) separately
Additional states for FY07
MN, MS, NJ, NY, RI, UT
CA – basin delineation and possibly basin characteristics in southern CA

19. Evaluation of Illinois StreamStats
Basin characteristics at 283 USGS rural gaging stations
Sensitivity of basin characteristics on estimated flood quantiles
Flood quantiles at 169 USGS rural gaging stations (random sampling)
Reliability testing

20. Arithmetic Scale
Log-Log Scale
Scatter plots of preliminary
Q100 estimates using
BasinSoft and manual
drainage basin delineation
with StreamStats
All regions, n = 164

21. Distribution of differences by Region
The UNIVARIATE Procedure
Variable: PERDIFFIL_Q100
Schematic Plots |
1 +
| *
0.5 +
| | *
| | | |
| |
0 + *--+--* *-----* *--+--* *--+--* *--+--* *--+--* *--+--*
| | | + | | |
| |
| | |
| |
REGION
Distribution of differences by Region
Differences are found not statistically
significant by paired t-test and
Wilcoxon Signed Rank test
(p-value < 0.05), except for
Region 1: Q2, Q5, Q10 percent
differences.
Variable: DIFFBSIL_Q100
Schematic Plots |
4000 +
| *
* *
| *
| | *
| | | | |
0 + *--+--* *-----* *--+--* *--+--* *--+--* *--+--* *--+--*
| | |
| * * * |
| * *
* * *
| * *
REGION
Mean
*----* Median
Interquartile Range
| x Interquartile Range
0 < 3.0 x Interquartile Range
* > 3.0 x Interquartile Range

22. Average absolute maximum deviation from the mode = 1.31 percent
Reliability Testing 1 2 3 4 5 6 7 8 9 10 11 12 13 14
5150
2050
1120
3010
2500
2280
4630
3870
4930
2800
3700
1160
575
7310
6120
2820
1180
583
2040
1760
2510
4940
11800
574
1980
1110
2490
319
1190
573
2830
580
6110
1150
4950
1170
2.94
0.89
0.4
0.2
0.71
2.54
0.09
1.39 15 16 17 18 19 20 21 22 23 24 25 26 27 28
6780
2050
1800
8440
4400
6420
5260
10100
14500
2230
2650
14300
5090
1700
6770
6430
2060
1790
17600
15300
7720
6860
14400
2220
2680
5100
1720
2040
4410
4810
0.15
0.49
0.56
0.23
0.16
0.69
0.45
1.13
5.5
1.18
Average absolute maximum deviation from the mode = 1.31 percent

23. Q100 = 1760
Q100 = 6110

24. StreamStats Development
Past
Massachusetts ArcViewIMS application
First prototype ArcHydro based Dec 2002
Development/Testing throughout
Idaho public release Oct 2004
Porting to ArcGIS Server
Web services
NHD Navigation/Reach indexing
Drainage-area ratio for ungaged sites
Weighted estimates for ungaged basins that cross state lines
Present

25. N

26. Flood frequencies estimated by regional equations and continuous simulation modeling in ungaged areas of the Blackberry Creek watershed, Kane County, Ill.

27. Actual rainfall and climatologic data
Overview approach for estimating the flood quantiles at sub-basins of the Blackberry Creek watershed
Flood frequency analysis
100
10000
1000
DISCHARGE, IN CUBIC FEET PER SECOND
0.01
0.10
1.00
10.00
30.00
50.00
70.00
99.00
99.90
99.99
90.00
PROBABILITY OF EXCEEDANCE, IN PERCENT
Actual rainfall and climatologic data
Flood quantiles QTs
Continuous simulation of rainfall-runoff using the HSPF Blackberry Creek watershed model
Simulated flow series at specified locations
Plot Title 50
100
150
200
250
300
350 20 40 60 80
120
140

28. To channels Precipitation Interception ET Depression Infiltration
Overland
flow
Land Use & Management
HSPF Sediment Module
HSPF PEST Module
Interflow
To channels

29. Blackberry Creek HSPF model
49 sub-basins with drainage area varying around 1 mi2 at the headwater, flows are routed through each basin
6 pervious land (PERLND): cropland, grassland, forested and wooded land, pervious residential, wetland, and barren and exposed land
3 impervious land (IMPLND): high density urban, impervious residential, and transportation

30. ¯ Thiessen Method for July 1996 Storm 24-hr rainfall = 6.59 in! #
THIESSEN
Yorkville
Montgomery
St. Charles (ISWS)
Aurora (NWS)
2.4
Miles
Blackberry
Watershed
Explanation
Stream Gage
Rain Gage
24-hr rainfall = in
24-hr rainfall = 6.59 in

31. Simulated July 1996 Flow (using Thiessen method) versus Observed Hourly Flow at Yorkville

32. NEXRAD Totals NWS Stage III July 17-18, 1996 EXPLANATION
48 hour Rainfall
(inches)
>
>
>
>
>
>
>
>
>

33. NEXRAD Totals Averaged to Watershed
July 17-18, 1996
EXPLANATION
48 hour Rainfall
(inches)
>
>
>
>
>
>
>
>
>

34. Simulated Flow (using NEXRAD) and Observed Hourly Flow at Yorkville

35. Comparison of Flow Duration Curves
Blackberry Creek at Yorkville
using Thiessen approach

36. Uses of the inundation map of the July 18, 1996, event for verifying flows in ungaged areas
Aerial video and pictures provided by Kane County and IDNR
Flood inundation mapping done by:
-Paul Schuch of Kane County
-Phil Gaebler of USGS

37. Verification with 1996 inundation map generated from video imagery—after routing with
HEC-RAS

38. Watershed Model Calibration and Verification
500
1000
1500
OBSERVED MONTHLY PEAK FLOW IN CFS
SIMULATED MONTHLY PEAK FLOW IN
CFS
y = 1.00 x R 2
= 0.80
Line of perfect agreement
and regression line
Calibration period
Coefficient of Model Fit Efficiency
Correlation Coefficient
Verification period
Coefficient of Model Fit Efficiency
Correlation Coefficient

39. Actual rainfall and climatologic data
Approach for estimating the flood quantiles at sub-basins of the Blackberry Creek watershed
Flood frequency analysis
100
10000
1000
DISCHARGE, IN CUBIC FEET PER SECOND
0.01
0.10
1.00
10.00
30.00
50.00
70.00
99.00
99.90
99.99
90.00
PROBABILITY OF EXCEEDANCE, IN PERCENT
Actual rainfall and climatologic data
Flood quantiles QTs
Continuous simulation of rainfall-runoff using the HSPF Blackberry Creek watershed model
Simulated flow series at specified locations
Plot Title 50
100
150
200
250
300
350 20 40 60 80
120
140

40. Five long-term precipitation records were evaluated for their representativeness of the watershed ( )
Exceedance probability in percent
0.1
1.0
10.0
30.0
50.0
Discharge in cfs
1000
10000
Regional flood-frequency curve
Lower95% of regional estimates
Upper95% or regional estimates
Argonne record
Aurora record
O'Hare record
Wheaton record
Elgin record
Blackberry Creek at Yorkville

41. Comparison of flood-frequency curves
between simulated and observed data ( )
Exceedence probability
0.1
1.0
10.0
30.0
50.0
70.0
90.0
99.0
99.9
Discharge, cfs 10
100
1000
10000
Legend
Observed Data 61-99
Lower95%
Upper95%
Observed Annual Peak-Data
Simulated with Argonne Data
Blackberry Creek at Yorkville

42. Thomas, (1986) — (~60 years flood series generated from lumped unit hydrograph model; Observed streamflow has at least 20 or more years of records)
Simulated AMS series underpredicted Q100 by 12% but overpredicted Q2 by 13% on average. The synthetic flood-frequency curves are flatter than observed flood-frequency curves
The model tended to underpredict flood peaks for small watersheds (1 mi2) and overpredict flood peaks for large watersheds (10 mi2)

43. Exceedance probability
0.1
1.0
10.0
30.0
50.0
70.0
90.0
Discharge, cfs
100
1000
214
12.5 km2
Exceedance probability
0.1
1.0
10.0
30.0
50.0
70.0
90.0
Discharge, cfs
100
1000
10000
280
177.7 km2
Exceedance probability
0.1
1.0
10.0
30.0
50.0
70.0
90.0
Discharge, cfs
100
1000
10000 51
32.5 km2
Exceedance probability
0.1
1.0
10.0
30.0
50.0
70.0
90.0
Discharge, cfs 10
100
1000
208
2.6 km2

44. Estimate of QTs in Ungaged Areas
Design storms
Event model
Event model
Synthetic frequency curves
Frequency analysis
Continuous simulation model
Regional
equations
streamstats.usgs.gov