Environmental Flowsin the

Guadalupe River Basin

Edwards AquiferRecovery Implementation Program,

Science Subcommittee

Environmental Flowsin the

Guadalupe River Basin

Edwards AquiferRecovery Implementation Program,

Science Subcommittee

Sam Vaugh, P.E.October 26, 2009Sam Vaugh, P.E.October 26, 2009

2

Topics of DiscussionTopics of Discussion

� Legislative Guidance

� Hydrologic Setting

� Environmental Flow Studies & Example Numerical Information

� Example Downstream Species of Interest

� Legislative Guidance

� Hydrologic Setting

� Environmental Flow Studies & Example Numerical Information

� Example Downstream Species of Interest

Legislative GuidanceLegislative Guidance

The “J” charge. . . Based on that analysis and the elements

required to be considered by the authority under Section 1.14 of this article, the expert science subcommittee shall . . .

Section 1.14. . . Authorizations to withdraw water from the

aquifer . . . shall be limited in accordance with this section to: . . . (2) protect the water quality of the surface streams to which the aquifer provides springflow; . . . (8) provide for instream uses, bays, and estuaries.

The “J” charge. . . Based on that analysis and the elements

required to be considered by the authority under Section 1.14 of this article, the expert science subcommittee shall . . .

Section 1.14. . . Authorizations to withdraw water from the

aquifer . . . shall be limited in accordance with this section to: . . . (2) protect the water quality of the surface streams to which the aquifer provides springflow; . . . (8) provide for instream uses, bays, and estuaries.

3

4

Average Annual Precipitation in the Guadalupe – San Antonio River Basin

(1961 – 1990)

Average Annual Precipitation in the Guadalupe – San Antonio River Basin

(1961 – 1990)

5

Major Aquifers and ReservoirsMajor Aquifers and Reservoirs

6

Storm Runoff and Spring Flows Satisfy Water Rights and Contribute to Instream Flows and Freshwater Inflows to the Guadalupe Estuary

Storm Runoff and Spring Flows Satisfy Water Rights and Contribute to Instream Flows and Freshwater Inflows to the Guadalupe Estuary

ComalSprings

ComalSprings

GuadalupeEstuaryGuadalupeEstuary

San MarcosSprings

San MarcosSprings

GuadalupeRiverGuadalupeRiver

7

0

100,000

200,000

300,000

400,000

500,000

600,000

700,00019

34

1936

1938

1940

1942

1944

1946

1948

1950

1952

1954

1956

1958

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

Year

Sp

rin

gfl

ow

(ac

ft/y

r)

Includes discharges from Comal, San Marcos, San Antonio, and San Pedro Springs.

Long-term Average = 337,113 acft/yr

Historical Springflow in the Guadalupe-San Antonio River Basin

Historical Springflow in the Guadalupe-San Antonio River Basin

8

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,00019

41

1943

1945

1947

1949

1951

1953

1955

1957

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

Year

Fre

shw

ater

Infl

ow

(ac

ft/y

r)

Average = 2,366,148 acft/yr (1941-1999)

Guadalupe Estuary — TWDB Historical Freshwater Inflow

Guadalupe Estuary — TWDB Historical Freshwater Inflow

9

Guadalupe Estuary —Freshwater Inflow ComponentsExample Average Year = 1994

Guadalupe Estuary —Freshwater Inflow ComponentsExample Average Year = 1994

10

Guadalupe Estuary —Freshwater Inflow Components

Example Dry Year = 1996

Guadalupe Estuary —Freshwater Inflow Components

Example Dry Year = 1996

Springflow Contribution to Guadalupe River During Drought (August 2006)

Springflow Contribution to Guadalupe River During Drought (August 2006)

� As reported in USGS Scientific Investigations Report 2008-5165, springflow accounts for:� 78% of Guadalupe River flow at Gonzales.� 70% of Guadalupe River flow at Victoria.

� Simplified calculations by HDR accounting for channel loss rates used in the Guadalupe – San Antonio River Basin Water Availability Model (GSA WAM) provide similar results.

� As reported in USGS Scientific Investigations Report 2008-5165, springflow accounts for:� 78% of Guadalupe River flow at Gonzales.� 70% of Guadalupe River flow at Victoria.

� Simplified calculations by HDR accounting for channel loss rates used in the Guadalupe – San Antonio River Basin Water Availability Model (GSA WAM) provide similar results.

11

12

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,00019

5619

5419

5519

6319

9619

8919

8419

5019

8819

5119

6419

4819

6219

9019

4319

9919

8019

5319

8319

5219

9519

8219

4719

6619

9419

7119

7819

5919

4919

7019

4519

6919

8619

4419

8519

6519

7219

7419

6119

4219

9119

9319

7519

4619

7719

9719

5819

6819

6719

6019

5719

7919

7619

8119

4119

7319

9819

8719

92

Year

Fre

shw

ater

Infl

ow

(ac

ft/y

r)

The three years with the lowest freshwater inflow occurred consecutively.

Six of the twelve years with the lowest freshwater inflow occurred during the 1947-1956 drought.

Guadalupe Estuary — TWDB Historical Freshwater Inflows

Guadalupe Estuary — TWDB Historical Freshwater Inflows

13

0

50,000

100,000

150,000

200,000

250,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Fre

shw

ater

Infl

ow

(ac

ft/m

o)

Medians computed for 1941 - 1999 historical period.

Guadalupe Estuary — TWDB Median Historical Freshwater Inflows

Guadalupe Estuary — TWDB Median Historical Freshwater Inflows

Environmental Flow StudiesEnvironmental Flow Studies

� San Marcos River near Leisure Camp (water rights permitting)

� Guadalupe River below Gonzales (TPWD & GBRA)

� Guadalupe River near Victoria (water rights permitting)

� Guadalupe Estuary (TPWD & TWDB, TAMU, UT Austin)

� San Marcos River near Leisure Camp (water rights permitting)

� Guadalupe River below Gonzales (TPWD & GBRA)

� Guadalupe River near Victoria (water rights permitting)

� Guadalupe Estuary (TPWD & TWDB, TAMU, UT Austin)

14

Environmental Flow Regime ElementsEnvironmental Flow Regime Elements

1) Subsistence Flowsa) Infrequent low flows.b) Provide restricted aquatic habitat.c) Maintain adequate levels of dissolved oxygen.

2) Base Flowsa) Average flow conditions, including variability.b) Provide suitable aquatic habitat.

3) High Pulse Flows4) Overbanks Flows

1) Subsistence Flowsa) Infrequent low flows.b) Provide restricted aquatic habitat.c) Maintain adequate levels of dissolved oxygen.

2) Base Flowsa) Average flow conditions, including variability.b) Provide suitable aquatic habitat.

3) High Pulse Flows4) Overbanks Flows

15

Guadalupe River @ Gonzales,Base Flows

Guadalupe River @ Gonzales,Base Flows

16

17

Guadalupe River @ Victoria,Base Flows

Water Quality ModelingWater Quality Modeling

18

Modeling to ensure maintenance of DO standard during summer stress period.

19

Water Quality Modeling

DO can be maintained during summer stress periods at flows well below the published 7Q2.

Guadalupe River @ Victoria, Subsistence Flows

Guadalupe River @ Victoria, Subsistence Flows

20

Example Endangered, Threatened, or Rare Species Known to Occur in

Downstream Counties

Example Endangered, Threatened, or Rare Species Known to Occur in

Downstream Counties

� American Eel – Calhoun, DeWitt, Refugio, � Blue Sucker – Caldwell, DeWitt, Gonzales� Cagle’s Map Turtle – DeWitt, Gonzales,

Guadalupe, Victoria� Guadalupe Bass – Caldwell, DeWitt, Gonzales,

Guadalupe, Victoria� Guadalupe Darter – Caldwell, DeWitt, Gonzales,

Guadalupe� Whooping Crane – Calhoun, Refugio

� American Eel – Calhoun, DeWitt, Refugio, � Blue Sucker – Caldwell, DeWitt, Gonzales� Cagle’s Map Turtle – DeWitt, Gonzales,

Guadalupe, Victoria� Guadalupe Bass – Caldwell, DeWitt, Gonzales,

Guadalupe, Victoria� Guadalupe Darter – Caldwell, DeWitt, Gonzales,

Guadalupe� Whooping Crane – Calhoun, Refugio

21

* 247 Adults & 22 Chicks Reportedly Migrating in 2009

* 247 Adults & 22 Chicks Reportedly Migrating in 2009

22

23

Questions & DiscussionQuestions & Discussion