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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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Presentation on theme: "Approaches to Establish Minimum Flows to Bays and Estuaries Paul Montagna Marine Science Institute University of Texas at Austin Port Aransas, Texas."— Presentation transcript:

1 Approaches to Establish Minimum Flows to Bays and Estuaries Paul Montagna Marine Science Institute University of Texas at Austin Port Aransas, Texas

2 Presentation Outline Case studies Lessons learned A Generic Methodology emerging?

3 Case Studies Nueces Estuary, Texas, USA San Francisco Bay, California, USA Caloosahatchie Estuary, Florida, USA Mtata Estuary, South Africa National Program, Australia

4 Nueces Estuary, Texas USA -Issues Second dam built ,000 acre-ft/y required. No releases due to drought and impoundment. Salinity increased 3 fold.

5 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.

6 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

7 Florida, USA -Water Management Districts Northwest Florida WMD St. Johns River WMD South Florida WMD * Suwannee River WMD Southwest Florida WMD

8 Caloosahatchie, FL USA -Issues Modifications (channels, canals, dams), diversions and withdrawals led to: Decreased sediment transport, biodiversity, and habitat. Increased eutrophication and hypoxia.

9 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

10 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.

11 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.

12 Mtata Estuary, South Africa -Issues 1998 National Water Act requires a r eserve 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.

13 Mtata Estuary, South Africa -Issues Storage capacity is 50% of mean runoff and only 8% reaches the sea.

14 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.

15 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 class 6. Set the quantity of the reserve and resource quality objectives. 7. Design resource monitoring program.

16 Mtata Estuary, South Africa -Approach Mtata had high scores because it was an Ecological Reserve so it has a high inflow requirement.

17 Australian National Program -Issues Laws requiring environmental flows to maintain health and biodiversity. Primarily state laws. Attempt to provide a consistent national approach.

18 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.

19 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.

20 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.

21 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).

22 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.

23 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.

24 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

25 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.

26 Generic Methodology -Adaptive Management Monitor appropriate ecosystem indicators. Reassess at appropriate intervals. (5 years?). Adjust management actions.

27 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?

28 Application of PSR Model PRESSURESTATERESPONSE -Stressors “Character- ization” -Ecological Services “Effects” -Agency Actions “Management”

29 Application of PSR Model PRESSURESTATERESPONSE -Stressors “Character- ization” -Ecological Services “Effects” -Agency Actions “Management” Human HealthMercuryNeurotoxicityReduce consumption

30 Application of PSR Model PRESSURESTATERESPONSE -Stressors “Character- ization” -Ecological Services “Effects” -Agency Actions “Management” Human HealthMercuryNeurotoxicityReduce consumption Ecological Health High salinityProductivity or species loss Set minimum flow levels


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