Transcript www.tceq.state.tx.us

Approaches to Establish
Minimum Flows to Bays and
Estuaries
Paul Montagna
Marine Science Institute
University of Texas at Austin
Port Aransas, Texas
Presentation Outline
Case studies
 Lessons learned
 A Generic Methodology
emerging?

Case Studies
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

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Nueces Estuary, Texas, USA
San Francisco Bay, California, USA
Caloosahatchie Estuary, Florida, USA
Mtata Estuary, South Africa
National Program, Australia
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
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Second dam built
1982.
151,000 acre-ft/y
required.
No releases due
to drought and
impoundment.
Salinity increased
3 fold.
150000
-1

Inflow Balance (Acre-ft month )
Nueces Estuary, Texas USA
-Issues
Post-Dam
Pre-Dam
100000
50000
0
-50000
-100000
1
2
3
4
5
6
7
Month
8
9
10 11 12
Nueces Estuary, Texas USA
-Approaches



Flow related to harvest with models to
choose minimal flow rate to sustain fishery
(i.e., the State methodology).
Minimum flow rules changed 3 times since
1990 (Adaptive Management).
Currently seeking mitigation strategies to
gain relief credit.
Nueces Estuary, Texas USA
-Restoration Efforts

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Nueces River bank lowered to
increase flooding of Rincon
Bayou and marsh.
Salinities reduced from 150
ppt to 25 ppt, productivity and
diversity increased.
City received inflow credit for
marsh restoration (Adaptive
Management).
Channel
Florida, USA
-Water Management Districts
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Northwest Florida WMD
St. Johns River WMD
South Florida WMD *
Suwannee River WMD
Southwest Florida WMD
Caloosahatchie, FL USA
-Issues

Modifications (channels,
canals, dams),
diversions and
withdrawals led to:
• Decreased sediment
•
transport, biodiversity, and
habitat.
Increased eutrophication
and hypoxia.
Caloosahatchie, FL USA
-Approach


Water Management
agency determined a
minimum flow to protect
habitat would protect
valued resources.
Recommended a minimum
flow level to protect salinity
sensitive seagrass species.
Shell Point
San Francisco Bay, CA USA
-Issues

Decreased
Sacramento-San
Joaquin River system
inflow led to
decreased
abundances of many
biotic components,
particularly five
threatened or
endangered fish
species.
San Francisco Bay, CA USA
-Approach

Workshop convened in 1991

Rule adopted in 1994 to ensure sufficient
inflow to locate the 2 psu isohaline
downstream to enhance estuarine
resources.
• Identified resource salinity ranges
• Relates inflow with salinity
Mtata Estuary, South Africa
-Issues

1998 National Water Act requires a
reserve to satisfy basic human needs
and to protect aquatic ecosystems.
• Basic human needs reserve: right of every
•
person to 25 litres of water of adequate
quality per day.
The ecological reserve: To protect rivers,
wetlands, estuaries and groundwater.
Mtata Estuary, South Africa
-Issues

Storage capacity
is 50% of mean
runoff and only
8% reaches the
sea.
Mtata Estuary, South Africa
-Approach

Developed a 7-step process relying on
value assessments (i.e., expert opinion)
to set a minimum flow.
• Geography, state, health, Reserve category,
hydrology, monitoring.
Mtata Estuary, South Africa
-7 Step Approach
1.
2.
3.
4.
5.
6.
7.
Delineate geographical boundaries.
Ecoregional typing.
Assess present state and reference condition.
Determine present ecological status and
importance using ecological health and
importance indices.
Determine ecological management class
Set the quantity of the reserve and resource
quality objectives.
Design resource monitoring program.
Mtata Estuary, South Africa
-Approach
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Mtata had high scores because it was an
Ecological Reserve so it has a high inflow
requirement.
Australian National Program
-Issues
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Laws requiring environmental flows to
maintain health and biodiversity.
Primarily state laws.
Attempt to provide a consistent national
approach.
Australian National Program
-Approach
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Basis:
• Check list of major ecological processes
•
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affected by flow to estuaries.
Adaptive management to assess risk
associated with reduced flows.
Two step methodology:
• Preliminary Evaluation Phase.
• Detailed Investigative Phase.
Australian National Program
-Approach

•
Preliminary Evaluation Phase:
1.
2.
3.
4.
Define environmental flow issue.
Assess estuary value.
Assess flow changes.
Assess estuary vulnerability.
Detailed Investigative Phase:
1.
2.
3.
4.
5.
6.
Model project impact on transport, mixing, quality, and
geomorphology.
Define environmental flow scenarios.
Use models to assess impacts of scenarios.
Assess biota risk.
License and development approval.
Adaptive Management.
Lessons Learned

Have to consider environmental needs prior to
construction of water projects:
•
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Preventing problems much cheaper than fixing problems.
Different approaches used everywhere:
•
•
Range from highly technical to highly value laden.
Valuing ecological services are the limiting factor, not
technology.
Restoration or minimum flow levels will never
approach natural conditions.
Emerging Generic Methodology?
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Have legal authority.
Have management goals based on
ecological services (i.e., ecosystem
management).
Monitor effects and reassess ecosystem
health (i.e., adaptive management).
Generic Methodology
-How To Start
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Identify your estuarine
typology and
geomorphology, climate
regime, and other physical
characteristics.
Identify your charismatic or
economically important
resources at risk.
Identify legal or
management frameworks.
Generic Methodology
-Starting Accomplishment
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Created the framework for justifying
environmental flows.
Created the approach for determining
environmental fresh water needs.
Identified the means to implementing a
minimum flow plan.
Generic Methodology
-Approach

Collect data:
• Long-term flow rates
• Size of rivers, streams, estuaries, bays
• Climate (rainfall and temperature) in
•

watershed
Long-term state of biological resources
Data not there?
• Don’t worry, you can start collecting now
Generic Methodology
-Approach Accomplishments
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Related inflow with fisheries.
Defined desired salinity regimes.
Related salinity regimes with valued
ecosystem components (VEC’s).
Identified minimum flow or elevation
levels related to something you want to
conserve.
Generic Methodology
-Adaptive Management
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Monitor appropriate ecosystem
indicators.
Reassess at appropriate intervals. (5
years?).
Adjust management actions.
Emerging Conceptualization


Use the risk assessment paradigm to set
environmental flows.
The Pressure-State-Response (PSR)
conceptual model is:
• Result of consensus building
• Long history
• Successful in regulation of environmental
health (i.e., water quality)

Can it be used for regulating water
quantity?
Application of PSR Model
PRESSURE
STATE
RESPONSE
-Stressors
“Characterization”
-Ecological
Services
“Effects”
-Agency
Actions
“Management”
Application of PSR Model
Human Health
PRESSURE
STATE
RESPONSE
-Stressors
“Characterization”
-Ecological
Services
“Effects”
-Agency
Actions
“Management”
Mercury
Neurotoxicity
Reduce
consumption
Application of PSR Model
Human Health
Ecological
Health
PRESSURE
STATE
RESPONSE
-Stressors
“Characterization”
-Ecological
Services
“Effects”
-Agency
Actions
“Management”
Mercury
Neurotoxicity
Reduce
consumption
High salinity
Productivity or
species loss
Set minimum
flow levels