Jim_Mead_WARS_6-29-10_ver_2

Determining Ecological
Flows for River Basin
Planning in North Carolina
Water Allocation Research Seminar
Raleigh - June 29, 2010
Jim Mead, NC Division of Water Resources
919/715-5428 [e-mail]
Presentation Overview
•Background – Instream & Offstream Uses
•Minimum Flows & Flow Regimes
•Site Specific Habitat Studies & Instream
Flow Requirements – what we do now
•Target Ecological Flows for River Basin
Planning
•NC Hydrologic Stream Classification
•Eno River Pilot Study
Instream Flow Needs
•What For?-to maintain instream uses
•Amount (cfs = 1.546 x mgd)
•Location – habitat type, species of interest,
drainage area, tributary inflow
•Time – monthly / seasonal / inter-annual
variation in water availability, critical life
stages, recreation season
Instream Uses
Water needs to remain in the channel for:
•Aquatic Habitat
•Water Quality
•Recreation
•Other – e.g. channel morphology,
temperature regime, salinity,
wetlands maintenance, aesthetics
Instream Flows Provide Habitat for a Diversity of Organisms
Roanoke River
Cheoah River
Flow Makes
a Difference
Offstream Uses
Require water to be removed
from the channel
•Consumptive – permanent
removal
•Bypass - temporary removal
Water Supply
Agriculture
Hydropower diversion
Thermoelectric Energy
As population increases, so
do offstream uses
Pressures on instream flows
and instream uses also
increase
SOME TERMINOLOGY
•Minimum flow
•Flow regime
•Ecological flow
•Instream flow requirement
•Target planning flow
Minimum Flows
•Minimum flows are just that – a minimal
threshold intended to maintain aquatic life for
relatively short periods of time
•The lower the minimum flow – the more it is
suited only to allow survival for brief periods
•Ecosystems suffer when the minimum flow
becomes THE flow for extended periods.
Flow Regime
•Incorporates the following components:
•magnitude
•timing
•frequency
•duration
•rate of change
•retains some degree of natural stream
flow variability
Ecological Flows
•Federal Clean Water Act – Declaration of Goals and Policy SEC. 101. (a) “The objective of this Act is to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.”
•Maintain ecological integrity – biological, chemical &
physical - “the ability to support and maintain a
balanced, integrated, adaptive community of
organisms having a species composition, diversity,
and functional organization comparable to that of the
natural habitat.”¹
¹Karr, J.R. and D.R. Dudley. (1981). Ecological Perspectives on Water Quality Goals.
Environ. Manage. 5:55-68
Instream Flow Requirement
•A site-specific, project-specific
determination
•Developed during preparation of
environmental documents and permit
reviews
•Incorporated in permits for water
resource projects – FERC, 401/404,
Dam Safety, EA/FONSI or EIS, CUA
ROCKY RIVER - REDBREAST SUNFISH HABITAT vs. DISCHARGE
0
5,000
10,000
15,000
20,000
25,000
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Discharge (cfs)
WU
A

(
s
q
.
f
t
.

p
e
r

1
0
0
0

f
t
)
Adult Juvenile Fry Spawning
HABITAT SUITABILITY INDICES - DEPTH
0.0
0.2
0.4
0.6
0.8
1.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
DEPTH (ft)
HS
I
GUILD=SHALLOW-SLOW with WOOD COVER
HABITAT SUITABILITY INDICES - VELOCITY
0.0
0.2
0.4
0.6
0.8
1.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
VELOCITY (fps)
HS
I
GUILD=SHALLOW-SLOW with WOOD COVER
Field Study
Physical Modeling
Habitat Modeling
Habitat vs. Flow
for each organism
Hydrologic Modeling
•Time Series Analysis
•Flow Alternatives
•Recommendations
Requires time and $
Site- and Project–specific Evaluations
Target Flows Used for
River Basin Planning
•If not included in the basin model, the
underlying assumption would be that all
flow in the stream – aside from any existing,
specific project-related flow requirements –
is available for withdrawal.
•Ecological planning flows are NOT intended
to replace in-depth, site-specific studies for
particular water project proposals –
especially those larger projects with more
complex environmental concerns.
River Basin Approach for
Long-range Planning
•Numerous locations throughout a basin
•Wide variety of streams – sizes, types
•One-size fits all approach to ecological
flows for the entire state is not
appropriate for North Carolina’s
diversity of rivers and streams
•Field studies at every location are not
practical
River Basin Approach for
Long-range Planning
•The offstream component is already
quantified in the model, using existing
water use data and projected increases
•For planning purposes, how do we
quantify the instream component? – to
evaluate water availability now and in
the future – instream and offstream
The First Step:
Developing a Hydrologic Stream
Classification System
•Hydrologic differences result in
ecological differences
•Sorting streams by hydrology also
sorts into ecologically distinct types
•DWR, WRC and EDF worked with
EFS to develop a hydrologic stream
classification system for NC
Hydrologic Stream Classification
System for NC
•Based on 231 USGS gages with at least 18
years of record
•Distinguished between relatively unaltered
and significantly altered gage records
•Examined 108 hydrologic variables,
identified 22 critical
•Can analyze USGS records or model output
NC Hydrologic Stream Classification
Workshop – December 2009
•Aquatic ecology and hydrology experts
from DWR, WRC, DWQ, NHP, USGS,
USFWS, NRCS, EDF, and EFS
•Introduction to classification analysis
and software
•Review of classes – sub-dividing, naming
•Future demonstration project
Stream Classes for NC
A. Coastal Streams
B. Small Stable Streams – cool & cold water
C. Large Stable Streams
D. Small Flashy Streams –
natural & accidental
E. Large Piedmont Rivers
F. Medium Stable Streams – cool & warm water
G. Small Seasonal Streams –
natural & accidental
A. Coastal Streams
B. Small Stable Streams
Cool & Cold Water
Ivy River
South River
C. Large Stable Streams
D. Small Flashy Streams
Natural & Accidental
Eno River
French Broad River
E. Large Piedmont Rivers
F. Medium Stable Streams
Cool & Warm Water
Cape Fear River
Tuckasegee River
Natural & Accidental
G. Small Seasonal Streams
Big Bear Creek0 cfs 32 cfs
But what does this have to do with Ecological Flows?
Why Classify?
•Different types = different habitat = different
ecological communities = different flow needs
•Ultimately – develop a specific technical
approach for determining ecological planning
flows for each of the 11 stream classifications
•Where USGS stream flow data is lacking, river
basin hydrologic models will be used to simulate
a record of daily stream flows that can then be
analyzed with the stream classification software
to determine the hydrologic classification
The Next Step: Eno River Demonstration Project
Eno River Demo
•A pilot project
•Eno River – Hillsborough and State Park sites
•Neuse River Basin Hydrologic Model
•Existing Habitat Models (updated)
•Evaluate the effects of different flow
management approaches on aquatic habitat
•Is this technique viable for developing
approaches for other stream classifications
and other basins?
Some Potential Alternate
Flow Management Approaches
•Minimum flows
•Setting a flow target that varies seasonally
or monthly, and allowing some variation
within bounds above and below this target.
•Setting the threshold for allowable
hypothetical withdrawals as the amount that
results in a change in the hydrologic stream
classification
•Percentage of inflow available for withdrawal
– may vary by season, include drought
protocol with higher percentage withdrawal
•Other approaches suggested by the analysis
Rivanna River - Charlottesville, VA ²
•Case study: meeting 50-yr water supply
demands and ecosystem needs
•56% increase in demand by 2055
•Three-pronged strategy
–Enlarge reservoir
–3-stage drought management plan
–Probalistic forecasting triggers
conservation
Rivanna River Example
•Under the new water supply plan, environmental
flow releases from South Fork Reservoir will:
–Range from 70–100% of natural inflow at least
90% of the time,
–Dropping to 30–50% of natural inflow only
during extreme droughts.
–These environmental flow releases will
substantially restore natural flow variability, as
compared to the static environmental flow
releases provided historically.
²Richter, B. D., and G. A. Thomas. 2007. Restoring environmental flows
by modifying dam operations. Ecology and Society 12(1): 12. [online]
URL: http://www.ecologyandsociety.org/vol12/iss1/art12/
Scientific-Technical
Workgroup
Policy-Implementation
Workgroup
Advisory Group
³
³ From Charlottesville City Council Work Session: Community Water Supply Plan 5/6/08
Ridge Schuyler, Director, Piedmont Program, The Nature Conservancy
Questions?
The new DWR ecological flows web page
is up and running at:
http://www.ncwater.org/Data_and_Modeling/eflows/