January 27, 2011 Summary Background on Delta Flow and Habitat Relationships Delta Stewardship Council Presentation by the Independent Consultant.

January 27, 2011

Summary Background on Delta Flow and Habitat Relationships

Delta Stewardship CouncilPresentation by the Independent Consultant

Influence of Flow on Ecosystem Processes

Flow recognized as critical driver in estuary systems

Native organisms adapted to range of habitat conditions

created/maintained by natural flow regimes

Range of flows support sufficient habitat area, diversity

and connectivity

Alterations to seasonal flows influence fish survival by

controlling extent, quality and continuity of rearing and

spawning habitat

Decreased flow volumes can impact aquatic habitats (i.e.

loss of available habitat area/volume, migration

obstructions, increased temperature)

Flows-Volume/magnitude-Seasonal/daily timing-Frequency-Ramping (rate of change)-Floodplain activation

Physical habitat-Functional wetted area-Food supply-Rearing/spawning -Depth and velocity-Access to functional riparian/floodplain areas-Substrate quality-Water quality

Biological Resources-Fish distribution and abundance

-Growth

-Survival

-Reproductive success

-Biodiversity

Direct effects

-Stranding-Inundation or dewatering of spawning areas-Displacement of fish and other organisms-Fish passage barriers/flows-Increased risk of predation

Other Factors -Harvest -Land Use -Climate -Predation -Contaminants

(Lewis et al. 2004)

• Key estuary processes/functions tied to freshwater flows

• Recent Delta environmental flows appear insufficient to support native Delta fishes and have encouraged non-native species

• Alterations of flows affect fish directly and indirectly:

o Fish are relocated by changes in flow, salinity, turbidity or temperature beyond physiological tolerances

o Fish are impacted by changes in habitat distribution or quality

o Distribution, species composition, and landscape features (patchy versus continuous habitat) are a function of salinity, depth (light attenuation), and hydrodynamics

Influence of Flow on the Delta Ecosystem

• Quantity, timing and quality of flows are linked directly to physical estuarine conditions – salinity, sediment (turbidity), dissolved and particulate material, aquatic plant communities, and nutrients

• Processes linked to estuarine conditions strongly influence species composition, abundance, distribution, and production (Peirson et al. 2002)

(Alber 2002)

Influence of Flow on the Delta Ecosystem

Freshwater Flow to the Estuary

Quantity

Timing

(variability)

Quality

Estuarine Conditions

Salinity Sediment Dissolved

material Particulate

material Temperature

Estuarine Resources

Species composition, abundance, distribution

Primary and secondary production

Ecological Processes in the Delta- Flow Driven Processes

• Flows affect the physical environment (solid arrows), which then influences the biotic environment (dotted and dashed lines).

(Kimmerer 2002)(Kimmerer 2002)

Ecological Importance of Delta Flows

• Numerous components of the Delta ecosystem respond positively to increased freshwater flow (Delta outflow/X2)

Mechanisms for Effects of Flow on Estuarine Biota

• Powerful impact on multiple species because flow controls numerous physical drivers

• Delta outflow and abundance relationships may be influenced by the following processes:

Mechanism/Process Foodweb Influence

Nutrient loading stimulating primary production

Bottom-up

Loading of organic matter Bottom-up

Location and compression of salinity gradient

Bottom-up

Benthic community shift Bottom-up

Migration cues Direct

Increased turbidity Indirect

Dilution of contaminants Direct or Indirect

Transport to rearing areas Direct

Decreased influence of export pumping

Direct

Increased area/access to suitable spawning or rearing habitat (spatial distribution)

Indirect

(Kimmerer 2002)

Historical Hydrology of Through-Delta Flows

• Delta outflows have been significantly reduced <50% of unimpaired flow has made it through the Delta as

outflow, in 14 of the last 22 years

75% unimpaired flow

• A single minimum flow level at all times of year does not provide adequate protection– Seasonally adjusted flow regime needed for ecological function

• Current D-1641 X2 Estuarine Standard inadequate • SWRCB recommended flow criteria (i.e. 75% unimpaired

flow for Sacramento River)• DFG Development of Estuarine Habitat Suitability Indicator

– Outflow, sediment concentration, food supply, and habitat area

• Other approaches include variable export to inflow (E/I) ratio objectives adjusted to seasonal needs and changing upstream hydrology

• Flow can be modified to benefit native fishes and is one of the few immediate actions available

• Criteria should include capacity to adjust/adapt to changing conditions and improved understanding

Prescribed Flows for Ecosystem Health

An Example of Prescribed Flows to Support Ecosystem Health

(Richter et al. 2006)

(shift from minimum flow to flow regime mimicking natural hydrograph)

Hierarchy of Recommended Approaches Linking Flows to Viability Criteria for Public Trust Species (Fleenor et al. 2010; TBI 2010)

1. Known flow-dependent mechanism

• floodplain inundation and growth of salmon or reproduction of splittail • dissolved oxygen in Stockton DWSC and salmon distribution

2. Statistically significant correlations

• abundance of numerous fish and invertebrate species associated with winter-spring outflow/X2

3. Flows associated with more productive historical periods

• higher outflows in the 1967-1984 period correspond to more abundant populations of public trust species

4. Unimpaired flows should be used to guide the development of flow criteria

• unimpaired flows and a less modified Delta geometry support native species