Norman D. Johns, PhD, National Wildlife FederationWarren Pulich, PhD, Texas State University

Bays in Peril:A Natural Inflow

Approach for Texas Estuaries

The Natural Flow Paradigm

“managing an ecosystem within its range of natural variability is an appropriate path to maintaining diverse, resilient, productive, and healthy systems” (Swanson et al. 1993)

general

Maintain “full natural range of variation of hydrologic regimes...”measured by – timing, frequency, duration, and rate of change of key biologically significant hydro events (Richter et al. 1997)

flows

3 step

Corpus Christi Caller-Times, Sept. 24, 2003

3 step

Galveston Bay Measured (Historical) Yearly Freshwater Inflows

-

5

10

15

20

25

30

1941

1944

1947

1950

1953

1956

1959

1962

1965

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

Inflo

w, M

illio

n ac

-ft/m

o

High Variability is Inherent

Galveston Bay Measured Freshwater Inflows

Galveston Bay - Historical Inflows, 1979-80

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

JAN-197

9FEB

MARAPR

MAYJU

NJU

LAUG

SEPOCT

NOVDEC

JAN-198

0FEB

MARAPR

MAYJU

NJU

LAUG

SEPOCT

NOVDEC

Mon

thly

Inflo

w, m

illio

n ac

-ft/m

o

Shrimp & Freshwater Inflows

NWF’s Ecologically Relevant Inflow Criteria

productivity maintenance- 4 month spring/early summer freshwater inflow pulse (a.k.a. “Freshete”)

1.

Oysters & Freshwater Inflows

NWF’s Ecologically Relevant Inflow Criteria

productivity maintenance- 4 month spring/early summer freshwater inflow pulse (a.k.a. “Freshete”)

1.

drought analysis – 6 consecutive months very low-inflows, between Mar. – Oct.

2.

WAM = Hydrology Tool

- predict inflows

- differing scenarios: Natural ConditionsCurrent UseFull Water RightsLevels of reuse

- monthly results

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

JAN-197

9FEB

MARAPR

MAYJU

NJU

LAUG

SEPOCT

NOVDEC

JAN-198

0FEB

MARAPR

MAYJU

NJU

LAUG

SEPOCT

NOVDEC

Mon

thly

Inflo

w, m

illio

n ac

-ft/m

o Natural

Full Permits, 50% Reuse

Assessing Springtime Freshwater Pulse

Years with low Spring Freshete - Galveston Bay

0

2

4

6

8

10

12

14

16

18

Natural Future, full permits, 50%reuse

year

s w

ith lo

w F

resh

ete

Degree of Alteration = 60%

0

5

10

15

20

1 20

5

10

15

20

1 20

5

10

15

20

1 2

productivity maintenance- spring Freshete

drought analysis - population survival

National Wildlife Federation Analysis of Estuary Inflows

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

JAN-19

64 FEBMAR

APRMAY

JUN

JUL

AUGSEP

OCTNOV

DEC

Fres

hwat

er In

flow

, mill

ion

ac-ft

/mo

Naturalized

WAM - Future, Full Permits, 50% reuse

Drought Tolerance Inflow

NWF’s Low Flow Assessment

[ MinQsal ]

Degree of Alteration > 500%(high)

No. of Extreme 6 mo. Droughts - Galveston Bay

0

1

2

3

4

5

6

Natural Future, full permits, 50%reuse

No.

of E

xtre

me

Dro

ught

s

Next StepsApplication to Regional Planning Process

Refinement of Criteria (time window, benchmark volumes based on natural stats.)

Further examine ecological relevance ofcriteria

Guadalupe Estuary - Worst of Drought Conditions

-

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

110,000JA

N-19

56

FEB-

1956

MAR

-195

6

APR-

1956

MAY

-195

6

JUN-

1956

JUL-

1956

AUG-

1956

SEP-

1956

OCT-

1956

NOV-

1956

DEC-

1956

Inflo

w (a

c-ft/

mo)

NaturalHistoricalFuture - Full Water Rights Use, 50% ReuseState of Texas' MinQsal Criteria