11 Feb 2013 ... Can LU intensification be N/P neutral or better? ... Runoff – quick flow ... Tukituki
at Tapairu Rd. TRIM observed. 0. 20. 40. 60. 80. 100. 1960.
Solution to Pollution – 11th February 2013, Massey University
Land use, nutrients and periphyton in the Tukituki River – the TRIM model Kit Rutherford NIWA, 82 Ford Rd, Napier
Acknowledgements NIWA: John Quinn, Bob Wilcock, Niall Broekhuizen HBRC: Adam Uytendaal, Husam Baalousha, Dougal Gordon, Ian Millner, Barry Lynch , Rob Waldron, Monique Benson Cawthron: Roger Young GNS-Science: Mike Toews, Maksym Gusyev …and uncle Tom Cobbley
Management questions Can LU intensification be N/P neutral or better? Can on-farm mitigation be done cost-effectively? Can WWTP upgrades be done cost-effectively? Are there other mitigations (eg dam releases)? Do we need to control N or P, or both? Etc…….
Scientific challenge – quantify the links between • on-farm & in-city practices • river nutrients, plants and health?
Catchment BNZ, GLEAMS E2 INCA SWAT CLUES
Farms OVERSEER (annual) SPASMO & APSIM (daily)
ROTAN
Streams Groundwater Tritium ageing MODFLOW (flow) FEM-WATER (flow, nitrogen)
QUAL2e, RIVMOD Periphyton Guidelines SPASM, SAL (daily)
TRIM_CATCHMENT • •
AGRIBASE (land use) OVERSEER (annual N/P losses) • Drainage – slow flow • Runoff – quick flow
Enter the TRIM model… TRIM_CATCHMENT Slow flow • MODFLOW groundwater catchments, lags • Groundwater attenuation Quick flow • Nearest stream – no lags • Attenuation Annual N and P stream inflows
Daily inflows statistical estimates based on monthly monitoring 1994-2012
TRIM_STREAM (daily) • • •
Dilution, scour, advection Nutrient spiraling Periphyton growth
𝑃𝑃𝑃𝑃𝑃𝑃 = 𝑎𝑎𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 −𝑏𝑏 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 2
y = 2240x-1.155 R² = 0.94
PET/Rainfall
1.5
Penman PET Priestley Taylor PET
1 y = 2130x-1.164 R² = 0.93
0.5
𝑃𝑃𝑃𝑃𝑃𝑃 𝐴𝐴𝐴𝐴𝐴𝐴 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 1 + 𝑤𝑤 𝑃𝑃𝑃𝑃𝑃𝑃 + 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝑃𝑃𝑃𝑃𝑃𝑃 1 + 𝑤𝑤
0 0
500
1000 Rainfall (mm/y)
1500
𝑃𝑃𝑃𝑃𝑃𝑃 𝑤𝑤 1 + 𝐴𝐴𝐴𝐴𝐴𝐴 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 1 + 𝑤𝑤 𝑃𝑃𝑃𝑃𝑃𝑃 + 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝑃𝑃𝑃𝑃𝑃𝑃
30 100
25
25 80
20
20 60
TRIM
15
observed
10 5 0 1960
1970
1980
1990
2000
2010
2020
Flow (m3/s) Flow (m3/s)
Flow (m3/s)
Tukituki at Tapairu Rd 30
Tukituki at at Red Bridge Waipawa RDS w=2
TRIM TRIMobserved observed
15 40 10 20 5 0 1960 0 1960
1970 1970
1980 1980
1990 1990
2000 2000
2010 2010
2020 2020
Max >400 years
Mean 12.5 years
Quick flow Quick flow attenuation /km MODFLOW MRT Slow flow Slow flow attenuation /year
Stream attenuation /km
OVERSEER kgN/y, kgP/y
Tukituki at SH50
Tukituki at SH50
1.2
0.2
SOE
0.6
TRIM
0.4
TP (gP/m3)
0.8
SOE
0.02
TRIM
0.2
1999
2009
2004
0.002 1994
2014
1999
2009
2004
2014
Porangahau at OruawharaRd
Porangahau at OruawharaRd 0.6
10
0.5
6
SOE TRIM
4 2
TP (gP/m3)
8
0.4 SOE
0.3
TRIM
0.2 0.1
0 1994
1999
2004
2009
0 1994
2014
1999
2004
Makaretu at SH50
2009
2014
Makaretu at SH50
2
0.5
SOE
1
TRIM
SOE
0.05
TRIM
0.5 0 1994
1999
2004
2009
0.005 1994
2014
1999
Tukituki at SH2
2009
2014
SOE TRIM
1
1999
2004
2009
2014
TP (gP/m3)
0.15
2
0 1994
2004
Tukituki at SH2
3
TN (gN/m3)
TN (gN/m3)
1.5
TP (gP/m3)
0 1994
TN (gN/m3)
TN (gN/m3)
1
0.1 SOE TRIM
0.05
0 1994
1999
2004
2009
2014
So N and P gets into the river – so what? Aesthetics Mayflies, stoneflies => midges, worms, snails Fish food quality decreases Oxygen and pH problems Fish kills? Toxic algae?
Plant biology 101 Biomass = Growth – Loss Loss = low at low flows Growth = high in summer (temperature, sunlight) Growth = high when N/P supply is high TRIM_STREAM needs to use a DAILY time step but TRIM_CATCHMENT predicts annual N & P inputs
1
1
0.1
0.1
lookup
0.01
Monthly monitoring concentrations lookup
0.01
DRP
DRP 0.001
0.001
0.0001 1/01/1994
0.0001 1
10
100
1000
10
10
1
1
0.1
0.1
1/01/1999
1/01/2004
31/12/2008
lookup TP
0.01 0.001
lookup TP
0.01
Resampled daily concentrations
Current annual load
0.001
0.0001 1
10
100
1000
0.0001 1/01/1994
1/01/1999
1/01/2004
31/12/2008
Future annual load
Future daily concentrations
Increased N/P inputs => higher growth rate High growth rate => biomass accumulates faster between floods => Biomass is high more often => maximum biomass is Higher NB Long periods of low flow => high biomass
even if N/P inputs are low
Calibration January 2011
P controls plant growth and biomass Evidence of P recycling or release
Questions addressed using TRIM_STREAM 1. How far from a source do nutrients elevate biomass? 2. Is N or P the limiting nutrient in the Tukituki?
nutrient
Case 1: no nutrient recycling (Thomann 1970)
periphyton distance
WWTP nutrient
Case 2: nutrient recycling (Chapra pers. comm.)
periphyton distance WWTP
Top reach – P limited Bottom reach – N limited Denitrification? Sediment P release?
Plant growth can’t explain N loss Denitrification? Confirmed by 2012 survey
Observed and predicted time series 16/05/2011
5/02/2011
0 28/10/2010
0.02 35
20/07/2010
prd 74km
11/04/2010
0.03
Biomass (gC/m2)
Tukituki @ Red Bridge
1/01/2010
16/05/2011
5/02/2011
28/10/2010
20/07/2010
11/04/2010
1/01/2010
DRP (g/m3)
0.05 prd 74km
Tukituki @ Red Bridge
0.04 30
25
20
15 10
0.01 5
0
Predicted benefits of reducing P inputs from the WWTP 60
0.1
50
30
28/09/1991
28/09/1991
12/03/1991
0
24/08/1990
0
5/02/1990
10
20/07/1989
0.02
12/03/1991
20
24/08/1990
0.04
40
20/07/1989
0.06
Current
1/01/1989
Biomass (gC/m2)
0.12
0.08
Consent
70
Current
1/01/1989
DRP (g/m3)
Tapairu Rd
Consent
5/02/1990
Tapairu Rd 0.14
Effects of intensification – no P mitigation
TRIM1 study (Rutherford et al. 2011)
Frequency of compliance with guidelines
TRIM1 study (Rutherford et al. 2011)
Problem • High plant biomass in summer low flows is not a new problem in cobble-bed East Coast rivers • Biomass = Growth - Loss • Increasing N/P supply increases growth rate • High biomass occurs more frequently
• Higher maximum biomass occurs • Decreasing flow reduces dilution and loss
Solutions • On-farm N/P loss control/reduction Stock exclusion, Riparian buffers and wetlands, Critical source area control Improved effluent irrigation etc
• Practical methods are available (e.g., AgResearch toolbox) • Adoption is patchy – Cost, Availability of information/technology
• Improved management of wastewater discharges – Cost for small municipalities
• Flushing flows – possible with a dam • Riparian shade – small streams only • No magic bullet • Combinations of measures required
Challenge Agree/implement combinations of mitigation measures so we can have…
…but not this (…too often)