HomeMy WebLinkAboutTNC_Final_RecommendationKimberly Meitzen, Ph.D.
A presentation to the NC Ecological Flows Science Advisory Board,
July 16th, 2013
TNC Environmental Flow Project Outline
1. Conduct literature review to develop flow-ecology relationships
for NC riverine biota and physical stream processes
2. Analyze changes
in (a.) flow patterns
and (b.) biota over
recent history of
flow impacts
5. Identify areas of conservation priority relative to freshwater
ecosystem resilience and vulnerability
6. Provide information and resources to the EFSAB for TNC
environmental flow recommendations
3b. Identify spatial
and temporal
patterns of flow
changes
4. Develop flow-ecology
criteria and flow
recommendations to protect
riverine ecosystem integrity
characteristic of NC’s biotic
and physiographic diversity
(Decision Support System for
Environmental Flows
DSSEF)
3a. Identify
patterns of biotic
changes
Biological Data Evaluation
What are the prevailing patterns of fish communities?
How have fish diversity and abundance at-a-site changed over time?
How has water-use affected fish diversity and abundance ?
Can we define a flow-ecology response relationship?
NC DWQ wadeable streams
Fish > 2 survey dates per site, 1992 - 2009
Biological Data Evaluation
River Basin Fish Sites Fish Diversity Fish Density
% of fish
represented
for each basin
Roanoke 27 58 1,218 50 %
Cape Fear 69 68 2,650 63%
Tar Pamlico 33 59 1,740 66%
Little
Tennessee 12 36 415 50%
NC DWQ wadeable streams fish survey data
Fish data: sites with > 2 survey samples
Species distribution by ecoregion
Wadeable stream sample sites only include sub-set
of all potential species present in a basin
Blue Ridge
Piedmont
Coastal Plain
Descriptive Info on Fish Survey Data
Diversity:
Avg.: 17
Range: 4-31
Abundance:
Avg.: 328
Range: 7 – 1670
Fish Distribution by Guilds
De
p
t
h
Velocity
Pool
Pool-Run
Riffle-Run
Margin
Riffle
Backwater
Guilds developed by
WRC for NC
Adult/Juvenile Count Total % Spawn Count Total %
backwater 14
17
backwater 20
22 13 backwater; pool 2 10 backwater; pool 2
backwater; pool-margin 1
pool 50
64 37
pool 29
36 21 pool; backwater 5 pool; backwater 4
pool; pool-margin 3 pool; margin 2
pool; pool-run 6 pool; pool-run 1
pool-margin 2 2 1 pool-margin 3 5 3 pool-margin; pool-run 2
pool-run 41
50 29
pool-run 32
42 24 pool-run; backwater 1 pool-run; backwater 1
pool-run; pool 2 pool-run; margin 2
pool-run; riffle-run 6 pool-run; riffle-run 7
riffle 12
15 9 riffle 13 21 12 riffle; riffle-run 3 riffle; riffle-run 8
riffle-run 19
25 14
riffle-run 41
47 27 riffle-run; pool-run 2 riffle-run; pool-run 2
riffle-run; riffle 3 riffle-run; riffle 4
riffle-run; riffle; pool-run 1
Calculated from fish presence data for Little Tennessee, Cape Fear, Tar-Pamlico, and Little Tennessee
Influence of Environmental Variables on Fish
Community Patterns
What influence do these 14 environmental factors have the on fish
community patterns in wadeable streams?
Physiographic (2):
drainage basin area, stream gradient,
Hydro-climatic variables (4):
precipitation, temperature, mean annual flow, mean annual flow velocity
Land use variables (2):
departure from natural conditions in the active river area and HUC 12
Habitat condition (3):
Statewide condition, ecoregional condition, Conservation Planning Tool condition
Biogeographic (3):
river basin, ecoregion, Ecological Drainage Units (EDUs)
Environmental Variables used in NMS
Environmental Variables
Range or
Categories Description/Source
Drainage Basin Area 0.82 - 872 Cumulative Drainage Basin (sq. km)
Stream Gradient 0.00001 - 0.03 Local NHD catchment slope calculated from USGS 30m DEM
Precipitation 1088 - 1785 USGS PRISM mean annual precip (mm)
Temperature 122 - 165 USGS PRISM AIR TEMP Model (area weighted mean annual temp in degree C * 1)
Mean Annual Flow 0.35 - 312 Mean annual flow (cfs) computed from unit runoff method
Mean Annual Flow Velocity 0.650 - 1.42 Mean annual velocity (fps) computed from unit runoff method
HUC 12 Land cover 0.85 - 3.66 % departure from natural land cover, z-scores (low = excellent, high = poor)
ARA Land cover 0.67 - 4.85 % departure from natural land cover in Active River Area (ARA), z-scores (low =
poor, high = excellent)
Statewide Condition 1.11 - 3.82 Summation of habitat condition from Burns et al. 2012, z-scores (low = poor, high =
excellent)
Ecoregional Condition 0.43 - 4.18 Habitat conditions relative to ecoregion from Burns et al. 2012, z-scores (low = poor,
high = excellent)
Freshwater Conservation
Targets 0.18 - 3.56 Natural Heritage Program Conservation Planning Tool results, z-scores (low = poor,
high = excellent)
River Basin 4 groups (1) Little Tennessee, (2) Cape Fear, (3) Tar-Pamlico, (4) Roanoke
Ecoregion 3 groups (1) Coastal Plain, (2) Piedmont, (3) Appalachian Blue Ridge
Ecological Drainage Units 6 groups
(1) Tennessee River-Blue Ridge, (2) Cape Fear River - Piedmont, (3)
Albemarle/Pamlico-Piedmont/Fall Zone, (4) Cape Fear River - Coastal Plain, (5)
Albemarle/Pamlico-Coastal Plain, (6) Upper Roanoke River
NMS Ordination of
Community Patterns
Variables r – Axis 1 r – Axis 2
Mean Flow 0.253 0.293
Mean Velocity 0.336 0.343
Stream Gradient 0.285
Precipitation 0.296 0.737
Temperature -0.875
ARA Land Cover -0.320
HUC Land Cover -0.624
Statewide Habitat Condition -0.423
Ecoregional Habitat Condition -0.332
CPT Habitat Condition -0.419
Variables p A
Ecoregion 0.000 0.128
Ecological Drainage Unit 0.000 0.227
River Basin 0.000 0.168
Pearson’s results for quantitative variables
MRPP results for categorical variables
77% of the variance explained
Axis 1 = 55%, Axis 2= 22%
Temperature, Precipitation, HUC 12 departure
from natural conditions, and Ecological
Drainage Units strongest control on
community patterns
Mean annual flow velocity and drainage basin
area were only variables without significance
Fish Diversity and Abundance Patterns and
Changes Over Time
Fish diversity and abundance changes over time
Plotted graphs for 141 fish sites, number of events
and dates vary between 1992-2009
Calculated Coefficient of Variation
(CV = st.dev. /mean)
Calculated direction of change:
1. Positive: values increased > 10%
2. Negative: values decreased > 10%
3. Minimal: < 10% change either direction
4. No Pattern: >10% changed, values fluctuated
R² = 0.6867
R² = 0.1636
0
200
400
600
800
1000
1200
0
5
10
15
20
25
30
Co
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Di
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Diversity
CountCape
Fear
Patterns of Fish Diversity Changes Overtime
1. Positive: species diversity increased > 10% (green)
2. Negative: species diversity decreased > 10% (red)
3. Minimal: < 10% change overtime (turquoise)
4. No Pattern: >10% changed, values fluctuated positive and negative (orange)
Patterns of Fish Abundance Changes Overtime
1. Positive: species diversity increased > 10% (green)
2. Negative: species diversity decreased > 10% (red)
3. Minimal: < 10% change overtime (turquoise)
4. No Pattern: >10% changed, values fluctuated positive and negative (orange)
Water Use and Fish Survey Sites
Only 10% (14 sites) of the 141 fish sites occurred downstream of a withdrawal
source, the other 90% occurred upstream of withdrawal source
Calculated relationship between withdrawals and fish diversity and
abundance for sites downstream of water use source
Cumulative withdrawal and return discharges: Catchment level flow alteration data (withdrawals and returns)
accumulated difference downstream through NHD+ catchment. Catchement level data courtesy of RTI, post-
processing of cumulative downstream calculations by TNC
Fish response to withdrawals
Fish response to withdrawals
5-10% species diversity decline relative to 10% mean annual flow withdrawal
25-30% species diversity decline with 50% mean annual flow withdrawal
Considerations: only 14 data points, mean annual flow calculated by unit-area-
runoff method, not controlling for other factors, inconsistent pattern with at-a-site
diversity responses
Recommend more fish survey points and accounting for LULC and water quality
0
5
10
15
20
25
30
0.06 0.25 1.00 4.00 16.00 64.00
Sp
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c
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s
D
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s
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y
Withdrawal as % Mean Annual Flow (log scale)
Fish Community Analysis
Strengths:
Useful for characterizing fish ecology of wadeable streams
Community analysis showed importance of hydro-climatic variables, EDU classification, and land use impacts
Supports the need and importance for protecting naturally variable flow regimes indicative of different hydro-climatic areas and EDU’s
Diversity and abundance response patterns help identify areas of concern and show potential for monitoring fish impacts from flow alteration
Need to better quantify land use effects on aquatic ecology to separate them from water –use (withdrawal and return) related effects
Fish diversity and withdrawal plots shows negative relationship
5-10% diversity decline with withdrawal > 10% of the mean annual flow
25-30% diversity decline with withdrawal >50% of mean annual flow
Weaknesses:
Only applicable to wadeable streams (50-34% of other fish species from each basin absent from the analysis, ex. anadromous fish)
Data limitation prevented including water quality and water use-related effects
Only fraction of the sites had these data associated with them
Few wadeable stream sites occur in proximity to monitored stream flow gages making it challenging to develop flow-ecology relationships
Stream Flow Changes Over Time
What are the changes in flow patterns over recent history?
How do they vary spatially (among gaging sites) and temporally (months) and
by flow magnitude (percentiles) ?
How can changes in flow patterns inform environmental flows?
63 USGS gages with 57 years of record, 1955 - 2012
Period 1 (recent historic conditions): 1955 – 1980 (25 years)
Period 2 (current contemporary conditions) : 1980 – 2012 (28 years)
USGS Stream Flow
Gages
Mean Daily Flow
IHA for calculating monthly
percentiles for both periods:
90th, 75th, 50th, 25th, 10th
% change between time periods
calculated post-processing
Mapped % change across the
state for each percentile
IHA Monthly Flow Duration Curves
Exceedance Probabilities for the 90th, 75th, 50th, 25th, 10th %tile Flows
CapeFear_02105769
Monthly Flow Duration Curves
Exceedance Probability
9590858075706560555045403530252015105
Fl
o
w
r
a
t
e
(
c
f
s
)
1,000
10,000
Annual (1976-2011)
October (1976-2011)
November (1976-2011)
December (1976-2011)
January (1976-2011)
February (1976-2011)
March (1976-2011)
April (1976-2011)
May (1976-2011)
June (1976-2011)
July (1976-2011)
August (1976-2011)
September (1976-2011)
10th 75th 25th 50th 90th
Mid-Range Flows
Wet
Conditions
High
Flows
Dry
Conditions Low
Flows
Change among percentiles between periods
10
100
1000
10000
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Di
s
c
h
a
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g
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(
c
f
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)
Contentnea Creek at Hookerton, 02091500, 733 mi2 (Map ID 47)
90%
75%
50%
25%
10%
90%
75%
50%
25%
10%
Hi
s
t
o
r
i
c
Cu
r
r
e
n
t
Understanding contemporary conditions and spatial and temporal patterns of
flow changes will inform management of sustainable water use and
environmental flow protection.
Plotting scheme for % change to percentile
0%
+ 25%
- 25%
months
O N D J F M A M J J A S
Example: % change to one percentile for one gage
Calculated % change for the 5 percentiles for each month
Grouped % change into 4 categories: 1) 0-25% drier, 2.) > 25% drier, 3.) 0-25%
wetter, 4.) >25% wetter (all 5 percentiles for every month – 60 metrics)
>25% drier or wetter is significant change (Kennard et al., 2010)
50% of months are drier
17% are wetter
33% are normal
Changes to the 90th percentile: highest flows
90th percentile flow magnitudes are increasing more than decreasing
Blue Ridge region most stable relative to high flow changes
Dam regulated high flow increases: Cape Fear below Lake Jordan, Neuse below
Falls, and Roanoke below Roanoke Rapids
Coastal Plain increased intensity of precipitation events?
Changes to the 75th percentile: wet conditions
Percentile with overall least amount of change
Blue Ridge region most stable relative to high flow changes
Coastal Plain increased intensity of precipitation events?
Dam regulated high flow increases: Cape Fear below Lake Jordan, Neuse below
Falls, and Roanoke below Roanoke Rapids
Changes to the 50th percentile: moderate flows
Median flows are indicative of central tendency and most prevalent flows
32% of gages have significantly drier conditions for more than half the year
Changes greatest in Piedmont and Coastal Plain, upper Roanoke an exception
Blue Ridge tending toward drier 50th percentile flows but still within range of
normal variability
Changes to the 25th percentile: low flows
Statewide decreases in 25th percentile flow magnitudes, 51% of gages showed
significant flow decreases with conditions being much drier >50% of the time
Most emphasized in Piedmont and Coastal Plain with exception of Roanoke Basin
Climate change and increased pressure on water resources
Changes to the 10th percentile: lowest flows
Statewide decreases in 10th percentile flow magnitudes, 57% of gages showed
significant flow decreases with conditions being much drier >50% of the time
Most emphasized in Piedmont and Coastal Plain with exception of Roanoke Basin
Climate change and increased pressure on water resources
The 10th percentile low flows need better protection from water users
10th 75th
25th
50th
90th
Statewide changes to flow conditions
10th 25th 50th 75th 90th
% of gages drier 57 51 32 3 2
% of gages wetter 2 0 2 3 10
Combo of drier and
wetter 10 5 6 14 11
% of gages out of range
of normal variability 68 56 40 21 22
Context for Environmental Flow
Recommendations
1. Protect flows from withdrawals > 10% of MAF
2. Preserve seasonal and inter-annual variability of
flow patterns
3. Protect ecoregional and river basin related
variability of flow patterns
4. Prevent further water use related impacts to 10th
percentile low flows
5. Protect headwaters
1. Protect the natural flow regime and specifically the seasonal and
ecoregional patterns of flow variability
Daily average allocation using presumptive standard Percent-of-Flow (POF)
Separate criteria for: 1.) normal and wet years, and 2.) drought years
2. Prevent further water use-related decreases to 10th percentile flows
Pass-by flow flow criteria for minimum flows based off of a P-O-F
3. Restrict withdrawals in drainages <25 sq.mi. and limit withdrawals to
drainages 25-50 sq. miles to set limit (e.g. 1 MGD avg. per day)
Statewide rule, protects headwaters and flow accumulation
All flow criteria should be established using the same period of record
Prevent climate, land use, and pre dam-related biases
Our study uses 1984-2012, 28 year contemporary record
Reasonable length record most indicative of “current prevailing conditions”
Decision Support System for Environmental
Flows (DSSEF): 3 Parts
Protect Natural Flow Regime
Allocate a percent of the monthly median flow to net water use
5% allowable in drought conditions
10% allowable in normal to wet conditions
Protects range of natural variability and normal periods of drought stress
Calculated from monthly medians, protects seasonal flow patterns
Amount available varies geographically
More indicative of prevalent conditions and central flow tendency
Consistently lower impacts than allocating 10% Mean Annual Flow
Following example show this recommendation relative to the 63 gages used in the
stream flow change analysis
Available MGD calculated from current statewide flow conditions from the
current period (1984-2012) and grouped by eco-region and compared to 10% of
Mean Annual Flow
Water available in million gallons per day (MGD)
Blue Ridge normal and wet years
10 % of median flow
Blue Ridge drought years
5 % of median flow
triangles = withdrawals exceed returns
circles = returns exceed withdrawals
triangles = withdrawals exceed returns
circles = returns exceed withdrawals
Calculated relative to 5 and 10% of the monthly median flow average
Compared to 10% of the Mean annual flow for reference
Water available in million gallons per day (MGD)
Piedmont normal and wet years
10 % of median flow
Piedmont drought years
5 % of median flow
triangles = withdrawals exceed returns
circles = returns exceed withdrawals
triangles = withdrawals exceed returns
circles = returns exceed withdrawals
Calculated relative to 5 and 10% of the monthly median flow average
Compared to 10% of the Mean annual flow for reference
Water available in million gallons per day (MGD)
Coastal Plain normal and wet years
10 % of median flow
Coastal Plain drought years
5 % of median flow
triangles = withdrawals exceed returns
circles = returns exceed withdrawals
triangles = withdrawals exceeds returns
circles = returns exceed withdrawals
Calculated relative to 5 and 10% of the monthly median flow average
Compared to 10% of the Mean annual flow for reference
Protect Natural Flow Regime
Allocate a percent of the monthly median flow to net water use
10% allowable in normal to wet conditions
5% allowable in drought conditions
Protects range of natural variability
Calculated from monthly means, protects seasonal flow patterns
Water available for use varies by month, basin area, river basin and eco-region
Limits additional water use effects in areas of existing use
Limits new water use effects in areas not currently altered
Calculated from median flow from the current altered record
More indicative of prevalent conditions and central flow tendency
Consistently results in less impact than 10% of Mean Annual Flow allocation
Defines allowable daily net water use
Amenable to management because it involves a set-amount that does not vary with daily flow, only monthly and annual flow patterns
Net of old and “new” allowances on top of existing users
Identifies area where no new use is available
Pass-by flows when flows decrease below a percent of the median
monthly flow
60% of median Jan-April (50% in drought years)
50% of median May-Dec (40% in drought years)
These flows correspond to the range between the 10-25th percentile flow
averages for the period of record and provide protection when flows
decrease below this range
Calculated with same flow record as the P-O-F daily avg. water allocations
Varies by month, drainage basin area, and ecoregion
Only implemented during infrequent low-flow episodes and droughts
Requires daily monitoring of flow conditions
Prevent water use related decreases to the
10th percentile flows
Protecting the 10th percentile low flows
Ceasing withdrawals when flows decrease below:
50% of the median monthly flow May-Dec (40% in drought years)
60% of the median monthly flow Jan-April (50% in drought years)
Graph is plotted relative to average 10th, 25th, 50th, 75th, and 90th for each month
Example is from the French Broad River
Environmental Flow Rules
1. Protect Natural Flow Regime
5-10% of median flow as net use, variable dependent on drought regimes
2. Prevent further water use-related impacts to the 10th percentile flow by using pass-
by flow in times of extreme drought and/or periodic low flow periods. Passby when
flow reach:
Normal years 50% of monthly medians May-Dec, 60% of the monthly
medians Jan-April
Drought years: 40% of monthly medians May- Dec, 50% Jan-April of
monthly medians
3. Drainage basin area withdrawal cut-off:
< 25 sq. mi. no withdrawals, 25-50 sq. mi. limit to 1-5 MGD
3. Manage use relative to climate conditions
Variable rules for normal/wet years and droughts
Flow Recommendations Derived from P-O-F
Approach Defined by Monthly Flows for a Given
Stream Reach of a River Basin Will Protect:
Blue Ridge
Coastal Plain
Piedmont
Ecological Variability among Eco-
regions, Basins, and Drainage Basin Sizes
De
p
t
h
Velocity
Pool
Pool-Run
Riffle-Run
Margin
Riffle
Backwater
Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug Sept
Life-history, biological cues,
behavior strategy, and/or
ecological functions of different
species, guilds, and other
biological and physical processes
Seasonal variability (inter and intra-annual)
Acknowledgements:
Rebecca Benner, Cat Burns, Analie Barnett, Eloise Kendy, Kat Hoenke, and Alex Cohn, TNC
Martin Doyle and Amy Pickle, Duke
Chris Goudreau, NCWRC
Tom Cuffney, USGS
Michele Eddy, RTI
Mary Davis, SARP
EFSAB Members and DWR