the selwyn river/waikirikiri
TRANSCRIPT
The Selwyn River/Waikirikiri
Living Lake Symposium
Scott Larned &
NIWA research team
Waikirikiri
Waikirikiri
Overarching question:
What are the ecological effects of flow variability?
•Perennial, intermittent, ephemeral reaches
•Run-off dominated, groundwater-dominated reaches
•Floods & droughts
•Effects of long-term water use
Complex hydrology:
Intermittence
Mid-range flow pulses
Longitudinal flow variability
Bed-moving floods
Flow variability:
Groundwater-surface exchange
Connection & disconnection
Historical trends
Variable aquifer & runoff input
Gaining river
GW discharge
Losing river
GW recharge
Hydrogeology framework
~ Neutral
Foothills Central Plains
- 4
00
m
+ 3
00
m
Mean sea level
Poorly-confined aquifers Confined aquifers
Waihora Kaitorete
Spit
Aquitards
Pacific Ocean
Coes Ford (since 1984)
Whitecliffs(since 1964)
Spot gauging sites
19 sites, 132 dates
2003 - 2008
Scott’s Rd (2005-2009)
Hydrological framework based on flow time series &
spot gauging
Well L36/0092
Well M36/0599
Flow permanence
0 10 20 30 40 50 60 70 0
20
40
60
80
100
Flo
w p
erm
an
en
ce
(%
)
Distance downstream (km)
Losing section Runoff & trib dominated
Gaining section Groundwater dominated
Hororata R confluence Selwyn R mouth
Hydrological framework – ELFMOD
ELFMOD for predicting flow time series at all points on rivers
Albarine River,
France
Orari River,
New Zealand
Methow River,
USA
ELFMOD
Longitudinal flow frequency profile
Longitudinal flow variability
Temporal variation in intermittence
Date
Flow-ecology relationships:
hydrological variables
Flow-ecology relationships:
ecological variables
Flow ecology relationships
Total Richness
0
5
10
15
20
EPT Richness
Taxa +
/- 1
SE
0
2
4
6
8
10
12
Diptera
Flow Permanence
0.0 0.2 0.4 0.6 0.8 1.0
0
2
4
6
8
10
12
Flow - ecology relationships
0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 1 . 2
0 . 0
0 . 1
0 . 2
0 . 3
0 . 4
0 . 5
0 . 6
0 . 7 M
ean tota
l fish d
ensity (
m-2
)
Flow permanence
Rarely used
by fish
R2 = 0.744
P < 0.001
Flow-ecology relationships (a sample)
Hydrological variable Ecological response Reference
Dry duration (d)
Dry duration (d)
Dry duration (d)
Dry duration (d)
Flow permanence (%)
Flow permanence (%)
Flow permanence (%)
Flow duration (d)
Flow permanence (%)
Flow permanence (%)
Dry reach length (m)
Flow rate (m3s-1)
Flow duration (d)
Flow duration (d)
Flow permanence (%)
Flow permanence (%)
Aquatic invertebrate richness
Aquatic invertebrate density
Sediment respiration
Esterase activity
Hyporheic invertebrate density
Hyporheic taxon richness
% Hypogean taxa
Fish species densities
Fish species richness
Total fish density
N & P retention
N & P retention
Aquatic invertebrate richness
Aquatic invertebrate density
Aquatic invertebrate richness
Aquatic invertebrate density
Larned et al. 2007.
Aq Sci 69: 554.
Datry et al. 2007.
Freshwat Bio 52:1452.
Davey & Kelly 2007.
Freshwat Bio 52:1719.
Datry & Larned 2008
CJFAS 65:1532.
Arscott et al. 2010
JNABS 29:530
Surface-groundwater interactions
Surface-subsurface interactions
Roles of shallow groundwater systems in water purification and other ecosystem services
Effects of river flow and river management on groundwater ecosystems and their services
Flow requirements for groundwater ecosystems and their services
Experimental river ecology
Nutrient additions to experimental gravel bars
Experimental river ecology
Invertebrate & fish responses to river drying
Water quality & periphyton
0 10 20 30 40 50 60 70
Nit
rate
(m
g/L
)
0
2
4
6
8
10
Distance downstream (km)0 10 20 30 40 50 60 70
DR
P (
mg
/L)
0.00
0.01
0.02
0.03
0.04
0.05
0 10 20 30 40 50 60 70
DS
iR (
mg
/L)
0
5
10
15
20
25
Distance downstream (km)0 10 20 30 40 50 60 70
Ele
ctr
ical co
nd
uciv
ity (
mS
/m)
0.0
0.1
0.2
0.3
0.4
Water quality changes with distance downstream
Losing
Losing Losing
Losing Gaining
Gaining Gaining
Gaining
Nitrate = 0.04(Dist) – 0.12 R2 = 0.76
Differences betw. Selwyn sections & flow states
DisC-L = disconnected, losing (u/s)
DisC-G = disconnected, gaining (d/s)
C-L = connected, losing (u/s)
C-G = connected, gaining (d/s)
Median
Outlier
95% CI
DisC-L DisC-G C - L C-G
Nit
rate
(m
g/L
)
0
2
4
6
8
10
ANZECC
DisC-L DisC-G C - L C-G
DR
P (
mg/L
)
0.00
0.01
0.02
0.03
ANZECC
Differences betw. Selwyn sections & flow states
DisC-L = disconnected, losing (u/s)
DisC-G = disconnected, gaining (d/s)
C-L = connected, losing (u/s)
C-G = connected, gaining (d/s)
DisC-L DisC-G C - L C-G
Inorg
an
ic N
:P
0
500
1000
1500
2000
29503000
Periphyton biomass
MfE guideline:
for biodiversity
MfE guideline
for trout fishing
Nutrient-limited periphyton
Sites
Flagpole Whitecliffs Scotts Rd Chamberlains Upper Huts
Peri
phyto
n b
iom
ass (
mg c
hl a
/m2)
0
100
200
300
Control
N
P
N&P
Intermittence trends
0
10
20
30
40
50
60
19
85
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
Year
Le
ng
th o
f w
ette
d r
ive
r (k
m)
Mean Minimum Series3 Series4
slope = -0.55 km yr-1
slope = -0.32 km yr-1
Experimental river ecology
Invertebrate dispersal and colonisation