1. HYDROLOGIC AND WATER QUALITY
MODELING OF SIMS BAYOU WATERSHED
USING HSPF
Norma E. Moreno
Civil and Environmental Engineering
University of Houston
SETAWWA CONFERENCE
Houston, TX
March 08 2010

2. OUTLINE
 Background
 Objectives
 Area of Study
 HSPF Model
 Methodology
 Results
 Development implications on E. Coli concentrations
 Conclusions

3. BACKGROUND
•E. coli concentrations in Sims Bayou frequently exceed Texas standards for
both geometric mean (126 MPN/dL) and single sample standard (394
MPN/dL)
•Sims Bayou is listed on the United States Environmental Protection Agency
(US EPA) 303(d) list as impaired stream for contact recreation.
•Upon implementation of the TMDL, it would be beneficial to foresee the
response of the water body to natural and anthropogenic changes.
•Several studies have been used to simulate flows and bacteria
concentrations, however very few studies have been performed to assess
water quality conditions under different development scenarios.
•The evaluation of different scenarios in the watershed will help in
determining effective alternatives in the reduction of E. coli and meeting
required standards.

4. OBJECTIVES
 Application of HSPF to Sims Bayou Watershed to
evaluate hydrology and water quality.
 Evaluation of the capabilities of the model in the
prediction of E. coli concentrations under different
development scenarios.

5. SIMS BAYOU WATERSHED
•Approximately 33 % of the area is tidally influenced
•Sims Bayou is developed with an average of 45% impervious areas (above tidal).
•Development of the watershed will affect both water quality and quantity

6. HYDRO-METEOROLOGICAL NETWORK

7. SIMS BAYOU AMBIENT WATER QUALITY
SIMS BAYOU E. coli PROFILE (Jan 2001 - Aug 2009)
1000000
100000
E. coli (MPN/dL)
Maximum
10000
Geometric Mean
Minimum
1000
Standard Geomean
(126 MPN/dL)
100
10
Downstream
1
16656 11135 15876 16655 11133 15877 15878 11132
WQMS ID
WQM Geometric Geometric Mean Single Sample Number of Samples % of Samples
Number of
STATION ID INDICATOR Mean Criteria concentration Criteria Exceeding Single Simple Exceeding
Samples
Bacteria (MPN/dL) (MPN/dL) (MPN/dL) Criteria (25%)
16656 EC 126 420 394 84 36 42.9%
11135 EC 126 953 394 82 59 72.0%
15876 EC 126 1547 394 75 63 84.0%
16655 EC 126 888 394 88 58 65.9%
11133 EC 126 1129 394 113 91 80.5%
15877 EC 126 880 394 84 59 70.2%
15878 EC 126 1216 394 84 63 75.0%
11132 EC 126 1666 394 103 95 92.2%

8. HSPF MODEL
 HSPF (Hydrological Simulation Program – Fortran) simulates for
extended periods of time the hydrologic, water quality, and
associated processes on pervious, impervious land, streams and well
mixed impoundments
 It is considered one of the first comprehensive watershed models and
it is distributed from EPA through BASINS or as a stand alone
module.
 Limitations:
 Complicated operation of the model
 1D Model - no suited for complex hydraulic systems
 Heavily parameterized (sensitive to many inputs)

9. METHODOLOGY
Point Sources of
1. SPATIAL DIVISON WATERSHED Bacteria:
•WWTPs,
2. PREPARATION AND INPUT DATA SERIES •Sanitary Sewer Overflows
Physical: •Septic Tanks
• Land use distribution
•Streams Characteristics
•WWTPs flows
•Meteorological: Non-Point Sources:
Rainfall •Build up and wash off algorithm
•Evaporation •Event Mean Concentrations (EMC) required
•Evapotranspiration

10. METHODOLOGY
3. RUN MODEL
All sub-watersheds
Jan 1999 to Dec 2007
4. HYDROLOGY CALIBRATION Statistics used:
Sub-watershed 2
Jan 1999 to Dec 2007
Model outputs compared to
observed data under different
scenarios:
•Total Volume
•Annual Calibration Parameters:
•Seasonal •AGWRC: Basic Ground Water
•Rainfall Events Recession Rate
•High Flows (>70th percentile) •RETSC: Retention Storage Capacity
•Low flows (<30th percentile) •UZNS: Upper Zone Nominal Storage
5. HYDROLOGY VALIDATION Sub-watershed 2
Jan 2008 to Jul 2008

11. METHODOLOGY BACTERIA CALIBRATION
1. RUN MODEL
All sub-watersheds
Jan 2001 to Dec 2007
Statistics used:
2. BACTERIA CALIBRATION
All Sub-watersheds
Jan 2001 to Dec 2007
Model outputs compared to
observed data under different
scenarios:
•High Flows (>70th percentile)
•Flows above median Calibration Parameters:
•Low flows (<30th percentile) Delivery Ratio:
•Flows below median Set at 80%

12. HYDROLOGY CALIBRATION
SIMS BAYOU CALIBRATED FLOWS
10000
Observed Flows at USGS flow gage 08075400
Modeled Flows at Sub-watershed 2
1000
Flow (ac-ft)
100
10
1
0.1
Jan-99 May-00 Sep-01 Feb-03 Jun-04 Nov-05 Mar-07
Date
OVERALL (1/1/1999 - 12/31/2007)
Total Volume Summer Volume Winter Volume Storm Volume 90th Perc. 30th Perc. 10th Perc. < 30th Per. >70th Per.
Data Source
(ac-ft) (ac-ft) (ac-ft) (ac-ft) (ac-ft/hr) (ac-ft/hr) (ac-ft/hr) (ac-ft) (ac-ft)
Observed 288442.8 95732.6 51312.3 22309830.2 4.3 0.7 0.6 5358.1 159105.6
Modeled 281835.0 84654.3 57350.1 23614168.9 5.1 0.7 0.5 8509.8 156812.3
Error 2.3% 11.6% -11.8% -5.8% -19.1% -2.6% 16.2% -58.8% 1.4%
ANNUAL BEHAVIOR (1999 - 2007)
Data Source 1999 (ac-ft) 2000 (ac-ft) 2001 (ac-ft) 2002 (ac-ft) 2003 (ac-ft) 2004 (ac-ft) 2005 (ac-ft) 2006 (ac-ft) 2007 (ac-ft)
Observed 17835.3 21877.4 50327.7 34125.8 30684.5 37997.6 15066.7 22883.4 58051.4
Modeled 15966.3 24611.5 55631.6 30179.3 29703.2 37203.8 13361.2 32342.9 43047.0
Error 10.5% -12.5% -10.5% 11.6% 3.2% 2.1% 11.3% -41.3% 25.8%

13. HYDROLOGY VALIDATION
VALIDATION RESULTS (01/01/2008 - 07/31/2008)
Total Volume Summer Volume Winter Storm Volume 90th Perc. 30th Perc. 10th Perc. < 30th Per. >70th Per.
Data Source
(ac-ft) (ac-ft) Volume (ac-ft) (ac-ft) (ac-ft/hr) (ac-ft/hr) (ac-ft/hr) (ac-ft) (ac-ft)
Observed 1.14E+04 1.75E+03 7.29E+03 2.28E+07 1.60 0.60 0.40 5.94E+02 9.11E+03
Modeled 8.54E+03 1.85E+03 4.35E+03 2.41E+07 0.96 0.48 0.44 6.85E+02 6.64E+03
Error 25.2% -5.9% 40.3% -5.5% 40.3% 19.3% -10.8% -15.3% 27.1%

14. BACTERIA CALIBRATION

15. BACTERIA CALIBRATION

16. BACTERIA CALIBRATION
SUB_W. 2 SUB_W. 3 SUB_W 4 SUB_W. 5 SUB_W 6
WQS 11135 WQS 15876 WQS 11133 WQS 11135 WQS 11132
Obs.5 Pred.5 Error Obs.6 Pred.6 Error Obs.5 Pred.5 Error Obs.5 Pred.5 Error Obs.5 Pred.5 Error
Overall GM1 1031.6 1183.7 -15% 1830.5 1161.2 37% 1277.4 1111.1 13% 1260.3 1130.1 10% 1760.1 1255.8 29%
High Flow GM 2 1587.3 1366.0 14% 3250.8 1380.7 58% 3448.6 1102.3 68% 3039.4 1244.0 59% 3119.9 1499.3 52%
Low Flow GM3 714.6 1428.5 -100% 824.4 1480.8 -80% 466.0 1448.9 -211% 473.8 1314.9 -178% 1305.4 1313.9 -1%
Flow > median GM 1149.0 1181.8 -3% 2479.3 1160.6 53% 1893.8 1076.2 43% 2038.9 1116.0 45% 2383.0 1389.9 42%
Flow < median GM 714.6 1428.5 -100% 824.4 1480.8 -80% 466.0 1448.9 -211% 473.8 1314.9 -178% 1305.4 1313.9 -1%
Log RMSE4 0.72 0.73 0.75 0.74 0.60
Low Flow RMSE3,4 0.83 0.65 0.80 0.66 0.57
High Flow RMSE2,4 0.60 0.77 0.79 0.79 0.64

17. EVALUATION OF E. coli CONCENTRATIONS UNDER
DIFFERENT DEVELOPMENT SCENARIOS
Upstream
Midstream
Downstream
Tidal Affected Sub-watersheds
0 1 2 4 Miles

18. EVALUATION OF E. coli CONCENTRATIONS UNDER
DIFFERENT DEVELOPMENT SCENARIOS

19. CONCLUSIONS
 Overall hydrologic and E. coli calibration errors were acceptable but the
obtained for low flow regimes were relatively high
 The limitations of the model when simulating E. coli under low flow regimes
could be caused by an overestimation of the load from sources that are
controlling in this condition
 The simulation of increased development on the watershed showed that the
concentration of E. coli show a significant increment compared to current values
until the watershed reaches a development (impervious levels) of 87% average
 Comprehensive hydrological models like HSPF allow the user to get a better
understanding about the watershed and can be used for evaluating strategies in
the reduction of E. coli

20. ACKNOWLEDGMENTS
 Dr. Hanadi Rifai
 The Ivanhoe Foundation
 My husband E.J.
 My friends: Divo, Anu, Nathan, Maria, Emil, Steve,
Bora, JJ, Daniel, and Megan