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