hydrologic change in the lower flint river basin and responses of freshwater mussels to drought s.w....
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Hydrologic Change in the Lower Flint River Basin and Responses of Freshwater Mussels to Drought
S.W. Golladay and D.W. Hicks
J. W. Jones Ecological Research Center, Newton GA
Study Area
Spring
Ichawaynochaway Lower Flint
Kinchafoonee andMuckalee Recharge Area
Upper FloridanAquifer
Rainfall = 52 inches/year
i
Runoff = 7 inches/year
Recharge = 10 inches/year
SW Georgia Hydrologic Cycle
Flint
ET = 35 inches/year
Upper Floridan Aquifer
Why Mussels?Number of Species
0 10 20 30 40
Total Species Endemic Species
Suwannee
Ochlockonee
Apalachicola
Choctawhatchee
Escambia
River Basin
- High diversity and endemism long recognized (Clench and Turner 1950’s)- Important to stream function- Sensitive indicators of stream degradation-Long term population declines and extinctions occurring- Named in litigation concerning water allocation and ESA
Jones Center Studies1999
- 46 sites on 12 tributaries- 14,873 mussels- 19 species found (of 29 historical)
- 3 endangered species
Shiny-rayedPocketbook
GulfMoccasinshell
Oval pigtoe
2001 Post Drought Survey
Objectives:
1) Determine the extent of regional changes in mussel assemblages due to the drought
2) Determine stream reaches likely to be adversely affected by drought
Site Selection
Criteria for Selection
- 20 sites surveyed
- Previously surveyed in 1999
- Previously supported diverse or abundant mussel populations
- Represent a range of stream size
Muckalee Ck
Kinchafoonee Ck
Chickasawhatchee Ck
Spring Ck
Results
Hydrologic and Geologic Classification
Fall Line Hills
Dougherty Plain
Fall Line Hills
Muckalee Ck
Kinchafoonee Ck
Chickasawhatchee Ck
Spring Ck
Box Plot of Mussel Abundance
Mann-Whitney Rank Sum Test p=0.05
Changes in Mussel Abundance
1999 to 2001
Muckalee Ck
Kinchafoonee Ck
Chickasawhatchee Ck
Spring Ck
Status of Mussels 1999 to 2001Common Species
Elliptio complanata
Elliptio crassidens
Toxolasma paulus
Uniomerus carolinianusVillosa lienosa
Villosa vibex
1999 (#/site) 2001 (#/site)
Flowing 226 314 p=0.02
Non-Flowing 181 71 p=0.01
Status of Mussels 1999 to 2001Endangered Species
Hamotia subangulataSites 11/7 Medionidus pencillatus
Sites 2/1
Pleurobema pyriformeSites 5/6
1999 (#/site) 2001 (#/site)
Flowing 3 6 p=0.2
Non-Flowing 27 2 p=0.1
Status of Mussels 1999 to 2001Special Concern Species
Elliptio purpurella
Lampsilis claibornensisQuadrula infucata
Strophitus subvexusVillosa villosa
1999 (#/site) 2001 (#/site)
Flowing 20 22 p=0.6
Non-Flowing 3 1 p=0.7
Conclusions
• Mussel mortality occurs during periods of low flow• Many mussel species are uncommon• Remaining populations are isolated
Questions
• Water use is high in the lower Flint, are we contributing to stream drying? • Was the 2000 drought unusual?• Is climate (rainfall) changing?• What is the extent of water use?• Are stream flows changing and associated with water use?
Expansion of Irrigation
Data from: Harrison, K.A. and A.W. Tyson. 2001. Irrigation survey for Georgia. Proceedings of Georgia Water Resource Conference.
Climate Analysis
- Monthly drought and rainfall data from NCDC region 7
- Historical drought frequency
- Compared pre- and post irrigation annual and seasonal rainfall
- 10 yr running averages for seasonal
Hydrologic Analysis
conserveonline.org
- Compared pre- and post irrigation flows (using 1975 as the beginning of irrigation)
- 1, 7, 30 day minimum flows
- 50 percentile flows
Long Term Gauging Stations
Rainfall Trends
Palmer Drought Severity1940 - 2008
Drought of Record
Lowest flow of record??
Regional Rainfall -- Annual
Region 7 Rainfall
Year
1940 1960 1980 2000
An
nu
al T
ota
l (c
m)
20
30
40
50
60
70
80
Pre-IrrigationPost Irrigation
Least annual rainfall
- Little annual change- Least annual rainfall during 1950’s drought
Regional Rainfall -- Seasonal
Spring -- Apr - Jun
1940 1950 1960 1970 1980 1990 2000
7
8
9
10
11
12
13
14
15
16
17
18
Summer -- Jul - Sep
Year
1940 1950 1960 1970 1980 1990 2000
Ra
infa
ll (i
nch
es)
7
8
9
10
11
12
13
14
15
16
17
18 Fall -- Oct - Dec
Year
1940 1950 1960 1970 1980 1990 2000
6
7
8
9
10
11
12
13
14
15
16
17
18
Region 7 Seasonal Rainfall
Winter -- Jan - Mar
1940 1950 1960 1970 1980 1990 2000
Ra
infa
ll (i
nch
es)
8
10
12
14
16
18
20
10 year averageaverage
10 year running average
Potential Human Impacts
Regional land-use 50-60% agriculture and mostly irrigated
Spring Creek Watershed
Ichawaynochaway Creek Watershed
GroundwaterPermits
Permitted 413 Mgal/dActual ~ 90 Mgal/d
Permitted 1.34 Bgal/dActual ~ 177 Mgal/d
Spring Creek Watershed
Ichawaynochaway Creek Watershed
Surface WaterPermits
Permitted 368 Mgal/dActual ~ 48 Mgal/d
Minimal
Streamflow Trends
1 Day Minimum Flows
Year1940 1960 1980 2000
CF
S
0
20
40
60
80
100
120
140
160
180
200
Median
75%
25%
Pre-IrrigationPost Irrigation
Spring Creek
- 46% decline in 1 day minimum flows
- 39% decline in 7 day minimum flows
- 42% decline in 30 day minimum flows
1 Day Minimum Flows
Year
1940 1960 1980 2000
CF
S
0
100
200
300
400
500
Median
75%
25%
Pre-IrrigationPost Irrigation
Ichawaynochaway Creek
- 40% decline in 1 day minimum flows
- 31% decline in 7 day minimum flows
- 9% decline in 30 day minimum flows
Ichawaynochaway at Milford
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Flo
w (
CF
S)
200
400
600
800
1000
1200
pre-50-percentile post-50-percentile
Spring Creek at Iron City
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Flo
w (
CF
S)
0
200
400
600
800
1000
1200
pre-50-percentile post-50-percentile
50 Percentile Flows
Loss of Storage?
Erosion and Runoff
Erosion and accelerated runoff
Excessive sediment
Spring Creek Watershed
Changes in the lower Flint River Basin
- Declining mussel populations
- Increasing isolation of mussel populations
- Declining minimum daily flows
- Altered seasonality of flows
Water use contributes to declining stream flows
Derivative indices (e.g. 7Q10) are changing.
Questions?
Freshwater Musselmigrating during drought