Water Resources Engineering

by David R. Maidment

• The challenges – floods, droughts, poor water quality

• What we are doing about them– engineering structures, better planning,

management• What we study

– Academic Program at UT

Flooding Manawatu, New Zealand

http://www.ourregion.co.nz/home.php

Bridges that Work

http://www.ourregion.co.nz/home.php

Bridges that don’t work

http://www.ourregion.co.nz/home.php

Small bridge on a country road is washed away

http://www.tsarp.com/

Most costly urban flood disaster in the history of the United States

Major Highways during Tropical Storm Allison

I-45 SouthI-10 West

http://www.chron.com/content/chronicle/special/01/flood/

Kayaking on US 59, Houston(Tropical Storm Allison)

http://www.chron.com/content/chronicle/special/01/flood/

Residential Flooding in Tropical Storm Allison

http://www.chron.com/content/chronicle/special/01/flood/

The Human Cost

Saving the wedding photos Cleaning out the car

http://www.chron.com/content/chronicle/special/01/flood/

5-day rain total (Tropical Storm Allison)

Harris CountyCity of Houston

12-hour rain total (Tropical Storm Allison)

Extreme Rainfall Statistics (Tropical Storm Allison)

73,000 houses and apartment buildings flooded

Watersheds

Watershed = area that drains to a particular river or stream network

Stream gaging station

Floodplain maps(White Oak Bayou, Houston)

What can we do about floods?

• Engineering structures– Dams and detention ponds to hold back flood

waters– Increase capacity of streams to carry floods

• Better flood planning– Create floodplain maps to define at-risk areas– Restrict building foundations are at least 1 foot

above 100-year flood elevation– Develop flood forecasting and warning systems

Regional Storm Water Regional Storm Water Modeling Program and Modeling Program and

Master Plan for San Master Plan for San AntonioAntonio

City ofSan Antonio

Modeling System

Rainfall Data:Rain gagesNexrad

Calibration Data:FlowsWater Quality

Geospatial Data:City, CountySARA, other

FloodplainManagement

IntegratedRegional Water

Resources planning

CapitalImprovemen

tPlanning

FloodForecasting

Water qualityplanning

San Antonio Regional Watershed Modeling System

“Bring the models together”

Nexrad Map to Flood Map in Arc 9 Model Builder FLO

ODPLAIN MAP

Flood map as output

Model for flood flow

Model for flood

depth

HMS

Nexrad rainfall map as input

3D Terrain Modeling

Floodplain Mapping: 3-D View

Water Supply and Droughts

http://agnews.tamu.edu/drought/pics.html

http://agnews.tamu.edu/graphics/drought98/TXrainAprJun98BG.html

Streamflow Conditions

http://tx.waterdata.usgs.gov/nwis/rt

What can we do about droughts and water supply issues?

• Water resource development– Reservoirs and well fields to supply water

• Better water resources planning– Senate Bill 1 (1997 Legislature) established 14

water planning regions in Texas– Water Availability Modeling– Drought forecasting (El Nino – Southern

Oscillation)

Improvements from Senate Bill 1:Water Modeling and Planning

• Before Senate Bill 1, water planning was done state-wide by TWDB

• SB1 established 14 water planning regional groups, who are now responsible for planning water supply in their area

Water Availability Modeling (TNRCC)

Improvements from Senate Bill 1: Water Availability Modeling

Rio Grande

Colorado

Brazos SulphurTrinity

Nueces

City of Austin

8000 water right

locations

23 main river basins

Inform every permit holder of thedegree of reliability of their withdrawalduring drought conditions (TCEQ)

CRWR Mission for Senate Bill 1

• CRWR (UT Austin) aids in the response to Senate Bill 1 by providing to TCEQ watershed parameters defined from geospatial data for each water right location

• These data are input by TCEQ contractors to a Water Rights Assessment Package (developed at TAMU) which determines the % chance that the water will actually be available at that location

• TCEQ sends the owner of the water right a letter specifying the availability of water

Water Rights in the Sulphur BasinWater right locationStream gage location

Drainage areas delineated fromDigital Elevation Models are used to estimate flow at water right locations based on flow at stream gage locations

Water Quality

Background of Clean Water Act• 1972 Clean Water Act prohibits any

discharge of pollutants without NPDES permit - (fishable and swimmable)

• 1987 Clean Water Act amended to require NPDES permits for stormwater discharges

• Permits require implementation of Best Management Practices (BMPs) to reduce pollutant discharges to “Maximum Extent Practicable”

Location of Impaired Waters

Austin Area Impaired Water Segments

• Bull Creek – Impaired macrobenthic community• Onion Creek – Depressed dissolved oxygen• Slaughter Creek – Impaired macrobenthic community• Waller Creek – Impaired macrobenthic community• Eanes Creek – Bacteria • Gilleland Creek – Bacteria• Taylor Slough – Bacteria• Spicewood Creek - Bacteria

What can we do about water quality?

• Water quality enhancement structures– Sand filters, wet ponds– Screening inlets to storm sewers

• Total maximum daily load (TMDL)– Comes from Clean Water Act– Pollution load that a water body can accept and

still maintain its beneficial uses (aquatic life support, recreation, water supply)

Requirements for Structural Best Management Practices (BMP’s)

• City of Austin – Required since 1981, mainly sand filters

• TCEQ – Requires removal of 80% of sediment in stormwater for Edwards Aquifer

• LCRA – Requires 70-75% removal of sediment, phosphorus, and oil & grease for Highland Lakes

TxDOT Sand Filter

Central Park Wet Pond (Austin)

Extended Detention Basin

Nueces Bay Zinc in Oyster Tissue TMDL Project

Corpus Christi

3,000Meters

Imane Mrini

Center for Research in Water Resources

The University of Texas at Austin

Total zinc in water-Inner Harbor

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

12/1/80 8/28/83 5/24/86 2/17/89 11/14/91

8/10/94 5/6/97 1/31/00

Date

Con

c (µ

g/L)

13430 13429 13432 13439

Mean = 37µg/L

Zinc loads to Nueces Bay

Outflow

Atmospheric deposition Wat = 18.67 kg/dNPS watershed loadings

Qwsh = 1.83 m3/sWwsh = 3.69 kg/d

Lake Corpus Christi loadQNR = 2.47 m3/sWNR = 4.27 kg/d

Nueces Bay

Permitted dischargesQpd = 16.55 m3/sWpd = 0.71 kg/d CP&L plant

WCP&L = 52.75 kg/d

Inner Harbor

Average Conc. (1982-2001) = 37µg/L

Q = flow of waterW = load of zinc

Physicochemical Reactions

Sediment-Water Exchange

Photochemical Reactions Inorganic Reactions

Organic/Biological Reactions

Atmospheric Deposition

Flux Flux

sunlight

Bioconcentration of Zinc

Total Zinc in water( ~ 47 g/L) 0.047 ppm

Zinc in sediment( ~ 100 mg/kg)

100 ppm

Zinc in Oyster tissue(~ 1100 mg/kg)

1100 ppm

Ratio = 23,400

Ratio = 11

Ratio = 2127

Academic Program at UT

• Required courses– CE 319F Elementary Fluid Mechanics – CE 356 Hydraulics

• Electives– CE 358 Ocean Engineering– CE 370K Water Chemistry – CE 374K Hydrology – CE 365K Hydraulic Design (Level II)

CE Faculty in Water Resources

• Randall Charbeneau (groundwater, hydraulic design

• Ben Hodges (hydraulics, hydrodynamics)• Lynn Katz (water chemistry)• Spyros Kinnas (fluid mechanics, ocean

engineering)• Daene McKinney (water resources planning)• David Maidment (hydrology, geographic

information systems)