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, Feb 17, 2004 http://www.ourregion.co.nz/home.php

Bridges that Work

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

Bridges that don’t work

Small bridge on a country road is washed away http://www.ourregion.co.nz/home.php

http://www.tsarp.com/ Most costly urban flood disaster in the history of the United States

Major Highways during Tropical I-10 West Storm Allison I-45 South 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 County City of Houston

12-hour rain total (Tropical Storm Allison)

Extreme Rainfall Statistics (Tropical Storm Allison)

73,000 houses and apartment buildings flooded

Watersheds

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

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 Modeling Program and Master Plan for San Antonio

City of San Antonio

San Antonio Regional Watershed Modeling System “Bring the models together”

Geospatial Data:

City, County SARA, other

Rainfall Data:

Rain gages Nexrad Modeling System

Calibration Data:

Flows Water Quality Floodplain Management Capital Improvement Integrated Regional Water Resources planning Planning Flood Forecasting Water quality planning

Nexrad Map to Flood Map in Arc 9 Model Builder

Flood map as output

FLO ODP LAIN MAP

Model for flood flow HMS Model for flood depth 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 8000 water right locations 23 main river basins Brazos Colorado Rio Grande Nueces Inform every permit holder of the degree of reliability of their withdrawal during drought conditions (TCEQ) Trinity Sulphur City of Austin

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 E C N TE R F OR RESE AR H C IN W ATE R RESOU RC E S • 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 Basin Water right location Stream gage location Drainage areas delineated from Digital 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 • 1987 Clean Water Act prohibits any discharge of pollutants without NPDES permit - (fishable and swimmable) amended to require NPDES permits for stormwater discharges • Permits require implementation of Best Management Practices pollutant discharges to “Maximum Extent Practicable” (BMPs) to reduce

Location of Impaired Waters

Austin Area Impaired Water Segments • Bull Creek – Impaired macrobenthic community • Onion Creek – Depressed dissolved oxygen • Slaughter Creek • Waller Creek – Impaired macrobenthic community – 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

-

Imane Mrini

Center for Research in Water Resources The University of Texas at Austin

Nueces Bay 3,000 Meters Corpus Christi U 18 1

Zinc loads to Nueces Bay Q = flow of water W = load of zinc NPS watershed loadings Q wsh W wsh =

1.83 m 3 /s

=

3.69 kg/d

Atmospheric deposition W at =

18.67 kg/d Total zinc in water-Inner Harbor

Lake Corpus Christi load Q NR W NR =

2.47 m 3 /s

=

4.27 kg/d

70.0

60.0

50.0

40.0

30.0

20.0

10.0

Mean = 37µg/L

0.0

12/1/80 8/28/83 5/24/86 2/17/89 11/14/9 8/10/94 5/6/97 1/31/00 13430 13429 13432 13439 Permitted discharges Q pd W pd =

16.55 m 3 /s

=

0.71 kg/d

Nueces Bay

Inner Harbor

CP&L plant W CP&L =

52.75 kg/d Average Conc. (1982-2001) = 37µg/L Outflow

Flux

Physicochemical Reactions

sunlight Atmospheric Deposition Photochemical Reactions Inorganic Reactions Organic/Biological Reactions Flux Sediment-Water Exchange

Bioconcentration of Zinc Ratio = 2127 Total Zinc in water ( ~ 47 m g/L) 0.047 ppm Ratio = 23,400 Zinc in sediment ( ~ 100 mg/kg) 100 ppm Ratio = 11 Zinc in Oyster tissue (~ 1100 mg/kg) 1100 ppm

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 engineering) (fluid mechanics, ocean • Daene McKinney (water resources planning) • David Maidment (hydrology, geographic information systems)