Marine Biology Fall 2005. Oceans Bays Estuaries Tidal Salt Marshes.
Approaches to Establish Minimum Flows to Bays and Estuaries
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Approaches to Establish Minimum Flows to Bays and Estuaries Paul Montagna Marine Science Institute University of Texas at Austin Port Aransas, Texas
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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. Nueces Estuary, Texas, USA - PowerPoint PPT Presentation
Transcript of Approaches to Establish Minimum Flows to Bays and Estuaries
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 studiesLessons learnedA Generic Methodology
emerging?
Case Studies
Nueces Estuary, Texas, USA San Francisco Bay, California, USA Caloosahatchie Estuary, Florida, USA Mtata Estuary, South Africa National Program, Australia
Nueces Estuary, Texas USA-Issues
Second dam built 1982.
151,000 acre-ft/y required.
No releases due to drought and impoundment.
Salinity increased 3 fold.
Month
1 2 3 4 5 6 7 8 9 10 11 12
Inflo
w B
alan
ce (
Acr
e-ft
mon
th-1
)
-100000
-50000
0
50000
100000
150000
Post-DamPre-Dam
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 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
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• Identified resource salinity ranges
• Relates inflow with salinity
Rule adopted in 1994 to ensure sufficient inflow to locate the 2 psu isohaline downstream to enhance estuarine resources.
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. Delineate geographical boundaries.2. Ecoregional typing.3. Assess present state and reference condition.4. Determine present ecological status and
importance using ecological health and importance indices.
5. Determine ecological management class6. Set the quantity of the reserve and resource
quality objectives.7. Design resource monitoring program.
Mtata Estuary, South Africa-Approach
Mtata had high scores because it was an Ecological Reserve so it has a high inflow requirement.
Australian National Program -Issues
Laws requiring environmental flows to maintain health and biodiversity.
Primarily state laws. Attempt to provide a consistent national
approach.
Australian National Program -Approach
Basis:• Check list of major ecological processes
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. Define environmental flow issue.2. Assess estuary value.3. Assess flow changes.4. Assess estuary vulnerability.
• Detailed Investigative Phase:1. Model project impact on transport, mixing, quality, and
geomorphology.2. Define environmental flow scenarios.3. Use models to assess impacts of scenarios.4. Assess biota risk.5. License and development approval.6. Adaptive Management.
Lessons Learned
Have to consider environmental needs prior to construction of water projects:• 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?
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
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
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
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
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
“Character-ization”
-Ecological Services
“Effects”
-Agency Actions
“Management”
Application of PSR Model
PRESSURE STATE RESPONSE
-Stressors
“Character-ization”
-Ecological Services
“Effects”
-Agency Actions
“Management”
Human Health Mercury Neurotoxicity Reduce consumption
Application of PSR Model
PRESSURE STATE RESPONSE
-Stressors
“Character-ization”
-Ecological Services
“Effects”
-Agency Actions
“Management”
Human Health Mercury Neurotoxicity Reduce consumption
Ecological Health
High salinity Productivity or species loss
Set minimum flow levels
