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HomeMy WebLinkAboutRecommendations_of_the_NC_EFSABInstitute for Emerging Issues March 21, 2014 Chris Goudreau N.C. Wildlife Resources Commission Background Session Law 2010-143 Requires DENR to develop basinwide hydrologic models for each of the 17 major river basins in NC Simulate flows to determine if adequate water is available to meet all needs, including essential water uses and ecological flows Does not: replace site-specific studies vary existing permits/licenses 2 What are Ecological Flows? The Session Law defines ecological flow as “the stream flow necessary to protect ecological integrity.” Ecological integrity is defined (in S.L.) as “the ability of an aquatic system to support and maintain a balanced, integrated, adaptive community of organisms having a species composition, diversity, and functional organization comparable to prevailing ecological conditions and, when subject to disruption, to recover and continue to provide the natural goods and services that normally accrue from the system.” “prevailing” not in original def. (Karr and Dudley 1981) 3 Ecological Flows Science Advisory Board SL 2010-143 directs DENR to “create a Science Advisory Board to assist the Department in characterizing the natural ecology and identifying the flow requirements.” Role: water resource planning recommend scientifically-based methods or approaches and ecological flow requirements Not a role: water-use permitting recommending how DENR responds to a water-availability issue advising DENR on how to use the EFSAB recommendations 4 Makeup of the EFSAB 1.Academic Research – Duke University 2.Agriculture – NC State University; NC Division of Soil and Water Conservation 3.Electric Public Utilities – Duke Energy Carolinas 4.Environmental NGOs – Environmental Defense Fund; The Nature Conservancy 5.Local Governments – Hazen & Sawyer; Mecklenburg County 6.NC American Water Works Association – CH2M HILL 7.NC Division of Water Resources 8.NC Division of Water Quality 9.NC Environmental Management Commission 10.NC Forestry Association – NC Forest Service; USDA Forest Service 11.NC Natural Heritage Program 12.NC Marine Fisheries Commission – East Carolina University; NC Division of Coastal Management 13.NC Wildlife Resources Commission 14.US Geological Survey 15.US Fish and Wildlife Service 16.US National Marine Fisheries Service Facilitation provided by N.C. State University’s Natural Resources Leadership Institute and NCSU Cooperative Extension Met 28 times between November 2010 and October 2013 5 Importance of Flow “Master variable” of riverine systems Determines water quality, biology, physical habitat, and energy transfer All components of the flow regime (magnitude, duration, frequency, timing, and rate of change), including natural variability, are important to maintaining ecological integrity Natural variability of flows includes intra-annual and inter-annual variability and consists of extreme low flows, low flows, high flow pulses, small floods, and large floods Collectively, these concepts are known as the “natural flow paradigm” 6 Flow Regime Tied to Ecology Base Flows Subsistence Flows Overbank Flows High Flow Pulses Conserve biological function Conserve biological diversity, habitat diversity and water quality Provide for life history and geomorphic processes Maintain floodplain Moisture and nutrients to floodplain Riparian recruitment Water quality tolerances Key habitat thresholds Flow-dependent habitat Bank storage/moisture Suitable temperatures & DO Fish spawning cues Maintain channel Sediment/nutrient transport Sound Ecological Environment 7 Flow Components Many studies have shown that altering one or more flow regime components can significantly impact biota 8 ELOHA (Ecological Limits of Hydrologic Alteration) Start with regional hydrologic models Identify stream types expected to respond differently to flow alteration Model ecological responses to flow alteration for each stream type Use ecological models with socially-determined objectives to decide on flow requirements Monitor outcomes, improve models, repeat 9 ELOHA 10 Advancing the Science: Stream Classification DWR worked with a consultant to characterize and classify North Carolina streams based on flow characteristics from USGS gage data Resulted in a classification scheme comprised of seven stream classes that generally reflected stream size and flow stability 11 Class Characteristics – Hydrologic 12 Advancing the Science: Stream Classification Problems Classes generated from hydrology derived from USGS gages often differed from hydrology created from the WaterFALL rain-runoff model Stream hydrology classification approach should not be extrapolated beyond the USGS gages to ungaged sites Dropped this approach 13 Characterizing Stream Ecology Covered in DENR basin water quality plans In light of other findings, EFSAB report gives summary descriptions based on eco-region and stream size 14 Basic Streams in NC Mountain •Less altered •Steep •Cold-Cool Piedmont •More altered •Moderate •Cool-Warm Coast •Less altered •Flat •Warm •Tidal / non-tidal Headwater •Drainage area <10 km2 •All parts of the state •Comprise majority of mileage •Limited hydrologic and biologic data 15 Types of Eco-flow Recommendations Minimum Flow Threshold Statistically-based Standard Percent of Flow Standard 16 Minimum Flow Threshold May be a single value or seasonally adjusted (e.g., South Carolina) Can be based on low-flow statistic (e.g., 7Q10) or a percentage of mean annual flow (MAF) Reduces inter- and intra-annual variability Can “flat-line” the hydrograph if withdrawal is large 17 Statistically-Based Standard Flow components include: Critical low, low, high flow pulses, small floods, high floods Wet, normal, dry years For each component, includes magnitude, duration, frequency, season Tied to ecologically significant events e.g., spawning, floodplain rejuvenation, fry/juvenile growth, migration, sediment movement, channel maintenance Hard to implement in a model 18 Percent of Flow Standard Remove X% of water flowing by for a given time step X generally 6 – 20% Time step can be daily, weekly, etc. X can differ by season Percent-of-flow is easiest way to maintain all five flow components and variability aka “flow-by” 19 Strategies to Determine Ecological Flows Reviewed many other states and regions Habitat response models Habitat quantity and quality are measured relative to flow Indirect and intermediate measure of expected biological response Biological response models Composition and structure of the biological community is measured relative to flow 20 Strategies to Determine Ecological Flows Coastal systems Low gradient and tidally-influenced streams function differently from other inland streams Flow may play a secondary role to other factors including tides, salt concentration, and community structure and function Approaches Inflow-based – keep flow within prescribed bounds Condition-based – set flow to maintain a specified condition (e.g., salinity) at a given point in the estuary Resource-based – sets flow based on the requirements of specific resources (e.g., shrimp) 21 Advancing the Science: Flow-Habitat Relationships Habitat response models Uses a suite of biota habitat preference curves to ensure that all types of habitat are represented PHABSIM Common habitat model Used in NC for hydro relicensing and water withdrawal studies 22 Flow-Habitat Studies in NC 23 Advancing the Science: Flow-Habitat Relationships 24 Advancing the Science: Flow-Habitat Relationships 25 Percent of Piedmont Sites not Protecting 80% of Habitat for Deep Guild 26 Percent of Mountain Sites not Protecting 80% of Habitat for Shallow Guild 27 Generally, flow scenarios that deviate most from the unaltered condition were least protective of habitat (i.e., more water is better) Less clear, which flow scenarios were consistently best when considering all permutations of region, season, guild group More could be done to expand the number of sites, but these are intensive efforts; the easiest sites have been done Advancing the Science: Flow-Habitat Relationships 28 Advancing the Science: Flow-Ecology Relationships Ecological integrity inferred from fish or benthic macroinvertebrate community structure metrics Two basic approaches Relate biological conditions to flow across a range of flow conditions (space for time) Relate changes in biological condition to flow at a site over time Organizations outside of the EFSAB tried both approaches and reported their results to the Board RTI International (RTI) and USGS – used space for time The Nature Conservancy – used both approaches 29 Advancing the Science: Flow-Ecology Relationships 649 fish and 1,227 benthos “wadeable” sites across NC RTI/USGS conducted numerous statistical analyses to find meaningful relationships between fish/benthos and flow metrics Significant relationships were found between six flow metrics and: Shannon-Weaver Diversity Index of the riffle-run fish guild EPT taxa richness Flow metrics – annual and seasonal ecodeficits and reductions in the average 30-day minimum flow Attempted to include other explanatory factors (e.g., stream size and basin characteristics), but these were unsuccessful 30 Fish Dataset NCDWQ wadeable streams data; not trout 31 32 Fish Benthos Advancing the Science: Flow-Ecology Relationships Ecodeficit – sum of reductions in flow between altered and unaltered flow duration curves Auto-correlation among 100+ flow metrics 33 Advancing the Science: Flow-Ecology Relationships The Nature Conservancy Fish diversity and abundance 141 wadeable sites in Roanoke, Cape Fear, Tar, and Little Tennessee basins Compared to flow for the period of 1992 – 2009 Many sites saw little change in fish diversity/abundance over time However, fish abundance and diversity declined in portions of the Cape Fear and Tar basins To understand the direct influence of water withdrawals, only sites located downstream of known water withdrawals were analyzed further (N=14) Negative relationship between fish diversity and the relative size of the water withdrawal; statistically significant, but low explanatory power 10% ↓in MAF → 5-10% ↓ in species diversity 50% ↓in MAF → 25- 30% ↓ in species diversity 34 Advancing the Science: Flow-Ecology Relationships 35 Advancing the Science: Coastal Considerations 36 Advancing the Science: Coastal Considerations EFSAB Recommendations: Ecological Flow Standard Percentage of Flow (1) Default statewide approach 80-90% of the instantaneous modeled baseline flow Why a range? No apparent threshold from habitat response analyses Flow-by percentages >80% were most consistently protective No consensus on a single flow-by percentage by the EFSAB Similar to values from other jurisdictions DENR discretion to select the most appropriate value for planning purposes 37 EFSAB Recommendations: Ecological Flow Standard Percentage of Flow (2) 38 EFSAB Recommendations: Ecological Flow Standard Percentage of Flow (3) “Instantaneous” = normal time step of the model (typically daily) Model cumulative effects to avoid impacts of a series of withdrawals 39 EFSAB Recommendations: Ecological Flow Standard Percentage of Flow (4) Combine with a critical low-flow component Protect the aquatic ecosystem during periods of drought Prevent increasing the frequency or duration of extreme low flows that are damaging to ecosystem health Use 20th percentile flow as a critical low flow (by month) Ecological flow threshold is the larger of the flow-by and critical low-flow values 40 EFSAB Recommendations: Ecological Flow Standard Percentage of Flow (5) Model should include following flow regimes natural (without any withdrawals or returns) baseline (with current withdrawals and returns) projected (with current and future withdrawals and returns) Comparisons baseline:natural = how much hydrology has already been altered baseline:future = effects of future withdrawals and returns Model updates should keep baseline as 2010 conditions to avoid comparisons to a continually shifting “current” condition 41 EFSAB Recommendations: Ecological Flow Standard Percentage of Flow (6) Run basin model with 2 hydrology datasets – full and trimmed (10-90%) 42 # times threshold exceeded Condition DENR Action Full Trimmed 0 0 Green None 1+ 0 Yellow Begin review of water usage that may be contributing to the deviations. Management tools, including water shortage and drought response plans, should be evaluated for the purpose of maintaining ecological integrity. 1+ 1+ Red Additional review could include actions such as conducting site-specific evaluations or review and modeling of any biological data that are available EFSAB Recommendations: Ecological Flow Standard Biological Response DENR should evaluate the use of these models to assess changes in biological conditions associated with projected changes in flow A 5-10% change in biological condition suggested as an initial criterion for further review Based on average range of EPT richness within the invertebrate condition classes (Excellent, Good, Good-Fair, Fair, and Poor) as defined by DENR The 5-10% criterion represents a change of one-quarter to one-half of the width of a condition class 43 EFSAB Recommendations: Ecological Flow Standard Biological Response 44 19% ∆ 7% ∆ Exceeds 10% “flag” EFSAB Recommendations: Ecological Flow Standard Exceptions – Coastal No numerical standards proposed Consider the following 45 Origin Gradient Ecological Flow Approach Statewide Recommendation Habitat Relationship Downstream Salinity Overbank Flow Piedmont Medium X X X Coastal Plain Medium X X X Coastal Plain Low X X X Coastal Plain Wind or tidally driven flow X X EFSAB Recommendations: Ecological Flow Standard Exceptions – Headwaters Streams with drainage basins <10 km2, DENR should conduct additional analyses to determine the potential for impact Limited biological and hydrologic data Higher vulnerability to disturbance Statewide approach may not adequately protect 46 EFSAB Recommendations: Other Listed Species For planning purposes, portions of basins (e.g., nodes) that include listed species should be treated by DENR as needing additional analysis in consultation with WRC, NMFS and USFWS Adaptive Management Emphasize new data (hydrologic and biological) collection and evaluation in headwaters, in the coastal plain, and in large rivers Validate ecological thresholds Track impact of flow changes Modify characterizations, target flows, and thresholds based on new data, changing conditions and lessons learned 47 Thanks! DWR Website of EFSAB: http://ncwater.org /?page=366 Chris Goudreau Special Projects Coordinator NC Wildlife Resources Commission 828-652-4360 chris.goudreau@ncwildlife.org 48