Download The Perennial, Intermittent, and Ephemeral Selwyn River, New

The Perennial, Intermittent, and Ephemeral
Selwyn River, New Zealand
Scott Larned, Mike Scarsbrook, Dave Kelly,
Graham Fenwick, Thibault Datry
National Institute of Water & Atmospheric Research
The Selwyn River
catchment
New
New
Zealand
New
Zealand
Zealand
North
Isl.
South
Isl.
Canterbury Plains & Southern Alps
Irrigation Trends in New Zealand
Irrigation demand predicted to increase 28% by 2010
Source: Growing for Good, Parliamentary Commissioner for the Environment 2004
Drought Predictions in New Zealand
30 mm Potential Evapotranspiration Deficit (PED) ≅ 1 month water deficit
(Mullen et al. 2005. NIWA report for MfE)
Aquifer-controlled alluvial plain rivers
Losing reach
Coastal mountains
Alluvial plain
Gaining reach
Modern sea stand
Sea level
Unconfined aquifer
Fluvio-glacial
gravel
Confined aquifers
Marine clay & sand
aquicludes
Ma’akua Stream, O’ahu, Hawai’i
Major aquifers of New Zealand
TASMAN
N
MARLBOROUGH
N
NORTHLAND
WEST COAST
AUCKLAND
CANTERBURY
BAY OF PLENTY
WAIKATO
GISBORNE
TARANAKI
OTAGO
HAWKES BAY
MANAWATU/
WANGANUI
SOUTHLAND
WELLINGTON
40
0
40
80 km
Region Boundaries
Lakes
Aquifers
Reproduced with permission of IGNS
50
0
50
100 km
Region Boundaries
Lakes
Aquifers
Losing reach
Quaternary gravels
- 300 m
+ 250 m
Selwyn River longitudinal cross-section
Gaining reach
Lake Ellesmere
Kaitorete
Spit
Mean sea level
Aquitards
Unconfined aquifer
Confined aquifers
Pacific
Ocean
Selwyn RiverSelwyn
reaches
& mainstem
sampling sites
River
Sampling site
Flow recorder
Perennial
Ep
he
m
er
Tributary springhead
Confluence
al
Unconfined Confined
aquifers
aquifer
N
0
5
10km
Inte
rmit
tent
Pere
nnia
l
July 2004
March 2005
River km 12
November 2003
River km 26
January 2004
Aims of study
• Compile baseline hydrologic, biologic, and
chemistry data
• Relate biological and chemical conditions
to hydrologic controls (e.g., flow permanence,
groundwater level)
• Conduct experiments to identify mechanisms
• Predict effects of future changes in water availability
on aquatic ecosystems
Hydrologic data collection
• River flow
–Continuous flow recorders
–Spot gauging
• Surface water presence/absence
–Airphotos
–Site visits
–Temperature loggers
• Groundwater & hyporheic water level
–Well network
–Mini-wells
Flow monitoring
NZ Hydrometric Network: high frequency,
long-duration, low spatial resolution
Flow monitoring
Pressure & velocity loggers:
high frequency, medium duration,
low spatial resolution
Flow monitoring
Spot gauging: low frequency, medium
duration, medium spatial resolution
Losing Gaining
Median Flows
Q50 (L/s)
2028
1199
High Flows
Relative Q10 (Q10/Q50)
3.1
4.9
30000
FRE 3 (per yr)
14
5
25000
DUR 3 (days)
3
11
50000
Losing
Whitecliffs AugReach
93-Oct 03
45000
40000
Q (L/s)
35000
20000
15000
10000
5000
0
Aug-93
Dec-94
May-96
Sep-97
Jan-99
Jun-00
Oct-01
Mar-03
50000
Coes Ford Aug 93-Aug 03
Gaining Reach
45000
40000
35000
Q (L/s)
30000
25000
20000
15000
10000
5000
0
Aug-93
Dec-94
May-96
Sep-97
Jan-99
Jun-00
Oct-01
Mar-03
Surface water presence
Airphotos: high spatial
resolution, low frequency
Surface water presence
Temperature loggers: low spatial
resolution, high frequency
iButton data 13 July – 10 Sept05
25
214.646 m ASL
20
214.861 m ASL
Temperature (C)
15
10
5
0
-200
50
300
550
800
1050
-5
Hours after 13July05, 1600 hrs
1300
1550
iButton data 15 – 27July05
18
16
214.646 m ASL
214.861 m ASL
Temperature (C)
14
12
10
8
6
4
2
0
0
50
100
150
200
250
Hours after 15July05, 0100 hrs
300
350
Surface water presence
Site visits: medium spatial
resolution, medium frequency
Longitudinal flow permanence
n = 40-51
Valley-plains
transition
Flow permanence (frequency)
1
Hororata R
confluence
0.8
Selwyn R
mouth
0.6
0.4
0.2
0
0
10
20
30
40
Distance downstream (km)
50
60
70
Groundwater level
Monitoring wells: high frequency,
low spatial resolution
700
14000
600
12000
500
10000
400
8000
300
6000
200
4000
100
2000
0
20/09/04
09/11/04
29/12/04
Date
17/02/05
0
08/04/05
Groundwater level (mm)
River flow (L/s)
Groundwater level data
Hyporheic water monitoring:
high frequency, med. spatial resolution
Hyporheic flow path monitoring
Ephemeral side
channel
Piezometers
+ iButtons
Wells
Selwyn River
main channel
Hyporheic flow path monitoring
• Subsurface water level and penetration
• Longitudinal changes in solutes, bacteria, and
invertebrates
• Relationships between water level, surface water, and
solutes, bacteria and invertebrates
July 2005
October 2005
Subsurface flow
in gravel bars
Losing reach
(river km 10)
Gaining reach
(river km 51)
Relating biological & chemical
processes to hydrologic controls
• Dissolved N in losing & gaining reaches
• Benthic invertebrates vs. flow permanence
• Bacterial activity & solute concentrations
along hyporheic flow paths
Nitrogen & conservative tracers in the mainstem
7
Mean
6
Outlier
5
95% CI
DON (mg N/L)
DIN (mg N/L)
0.32
4
3
2
0.24
0.16
0.08
1
0.00
16
12
Silicate (mg/L)
Sodium (mg/L)
0
14
10
8
6
4
losing
Losing
gaining
Gaining
12
8
4
0
Losing Gaining
Gaining
Losing
Invertebrate density & diversity
vs. flow permanence
30
15000
Riffles
Riffles
12000
Runs
25
Runs
Remnant Channels
Remnant Channels
20
R2 = 0.78
R2 = 0.49
9000
R2 = 0.77
R2 = 0.42
15
6000
10
R2 = 0.72
3000
0
5
0
20
40
60
Flow Permanence
80
100
0
0
Flow permanence (%)
20
40
60
80
100
Hyporheic carbon & bacteria
r2=0.77
0.006
r2=0.37
0.003
0
213.5
214.5
215.5
216.5
water surface elevation (m a.s.l.)
River
DOC (mg/L)
2
0.5
FDA (µmol/g/h)
Groundwater
3.5
Hyporheic processes in
experimental gravel bars
Summary
Hydrological Information
Precipitation
Relations with
ecological processes
Mechanistic
explanations
Runoff
Groundwater
Recharge
Abstraction
River
Recharge
Integration
Predictive modeling
Acknowledgements
• NIWA Field Team
• NIWA Analytical Labs
• Lincoln Ventures, Ltd
• Foundation for Research,
Science & Technology
• Cathy Kilroy, Kathy Walter,
Matt Dale, Glenn Cooper,
Karen Robinson (NIWA)
Tagliamento River, Italy
Hyporheic
water
surface
heights
in gravel
bars
Subsurface
water
levels
in gravel
bars