HYDROLOGIC AND WATER QUALITY MODELING OF SIMS BAYOU WATERSHED
USING HSPF
Norma E. MorenoCivil and Environmental Engineering
University of Houston
SETAWWA CONFERENCEHouston, TX
March 08 2010
OUTLINE
Background
Objectives
Area of Study
HSPF Model
Methodology
Results
Development implications on E. Coli concentrations
Conclusions
BACKGROUND
•E. coli concentrations in Sims Bayou frequently exceed Texas standards forboth geometric mean (126 MPN/dL) and single sample standard (394MPN/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 theresponse of the water body to natural and anthropogenic changes.
•Several studies have been used to simulate flows and bacteriaconcentrations, however very few studies have been performed to assesswater quality conditions under different development scenarios.
•The evaluation of different scenarios in the watershed will help indetermining effective alternatives in the reduction of E. coli and meetingrequired standards.
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.
•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
SIMS BAYOU WATERSHED
HYDRO-METEOROLOGICAL NETWORK
1
10
100
1000
10000
100000
1000000
16656 11135 15876 16655 11133 15877 15878 11132
E. c
oli
(M
PN
/dL)
WQMS ID
SIMS BAYOU E. coli PROFILE (Jan 2001 - Aug 2009)
STATION ID
WQM
INDICATOR
Bacteria
Geometric
Mean Criteria
(MPN/dL)
Geometric Mean
concentration
(MPN/dL)
Single Sample
Criteria
(MPN/dL)
Number of
Samples
Number of Samples
Exceeding Single Simple
Criteria
% of Samples
Exceeding
(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%
SIMS BAYOU AMBIENT WATER QUALITY
Maximum
Geometric Mean
Minimum
Standard Geomean
(126 MPN/dL)
Downstream
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)
METHODOLOGY
2. PREPARATION AND INPUT DATA SERIES
1. SPATIAL DIVISON WATERSHED
Physical:• Land use distribution •Streams Characteristics•WWTPs flows
•Meteorological: Rainfall •Evaporation•Evapotranspiration
Point Sources of Bacteria: •WWTPs, •Sanitary Sewer Overflows
•Septic Tanks
Non-Point Sources: •Build up and wash off algorithm
•Event Mean Concentrations (EMC) required
METHODOLOGY
4. HYDROLOGY CALIBRATIONSub-watershed 2Jan 1999 to Dec 2007Model outputs compared to observed data under different scenarios:•Total Volume•Annual•Seasonal•Rainfall Events•High Flows (>70th percentile)•Low flows (<30th percentile)
5. HYDROLOGY VALIDATION Sub-watershed 2Jan 2008 to Jul 2008
3. RUN MODELAll sub-watersheds Jan 1999 to Dec 2007
Calibration Parameters:•AGWRC: Basic Ground Water
Recession Rate•RETSC: Retention Storage Capacity•UZNS: Upper Zone Nominal Storage
Statistics used:
METHODOLOGY BACTERIA CALIBRATION
1. RUN MODELAll sub-watersheds Jan 2001 to Dec 2007
2. BACTERIA CALIBRATIONAll Sub-watershedsJan 2001 to Dec 2007Model outputs compared to observed data under different scenarios:•High Flows (>70th percentile)•Flows above median•Low flows (<30th percentile)•Flows below median
Calibration Parameters:Delivery Ratio:Set at 80%
Statistics used:
HYDROLOGY CALIBRATION
OVERALL (1/1/1999 - 12/31/2007)
Data SourceTotal Volume
(ac-ft)
Summer Volume
(ac-ft)
Winter Volume
(ac-ft)
Storm Volume
(ac-ft)
90th Perc.
(ac-ft/hr)
30th Perc.
(ac-ft/hr)
10th Perc.
(ac-ft/hr)
< 30th Per.
(ac-ft)
>70th Per.
(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%
0.1
1
10
100
1000
10000
Jan-99 May-00 Sep-01 Feb-03 Jun-04 Nov-05 Mar-07
Flo
w (
ac-
ft)
Date
SIMS BAYOU CALIBRATED FLOWS
Observed Flows at USGS flow gage 08075400
Modeled Flows at Sub-watershed 2
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%
HYDROLOGY VALIDATION
VALIDATION RESULTS (01/01/2008 - 07/31/2008)
Data SourceTotal Volume
(ac-ft)
Summer Volume
(ac-ft)
Winter
Volume (ac-ft)
Storm Volume
(ac-ft)
90th Perc.
(ac-ft/hr)
30th Perc.
(ac-ft/hr)
10th Perc.
(ac-ft/hr)
< 30th Per.
(ac-ft)
>70th Per.
(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%
BACTERIA CALIBRATION
BACTERIA CALIBRATION
BACTERIA CALIBRATION
SUB_W. 2
WQS 11135
SUB_W. 3
WQS 15876
SUB_W 4
WQS 11133
SUB_W. 5
WQS 11135
SUB_W 6
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
0 2 41 Miles
Upstream
Midstream
Downstream
Tidal Affected Sub-watersheds
EVALUATION OF E. coli CONCENTRATIONS UNDER DIFFERENT DEVELOPMENT SCENARIOS
EVALUATION OF E. coli CONCENTRATIONS UNDER DIFFERENT DEVELOPMENT SCENARIOS
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
Dr. Hanadi Rifai
The Ivanhoe Foundation
My husband E.J.
My friends: Divo, Anu, Nathan, Maria, Emil, Steve,Bora, JJ, Daniel, and Megan
ACKNOWLEDGMENTS