This document summarizes a study that used bio-economic optimization to model land use changes needed to reduce salt loads in the Simmons Creek catchment in Australia. The study used modeling tools like APSIM and FLUSH to simulate the hydrology and estimate salt delivery under different land use scenarios. It then used linear programming to determine the optimal land use changes across the 17,700 hectare catchment needed to reduce the salt load to specified targets. The results showed the amount and location of land use changes required, their costs in terms of reduced farm income, and that policy interventions may be needed to incentivize farmers to voluntarily make these changes given issues like inequity and cost. The study provided insights into using an integrated biophysical

1. Bio-economic optimisation of land
use to manage natural resources
Iain Hume, Tom Nordblom, John Finlayson,
Hamish Creswell, Enli Wang
WCCA – Brisbane- 29 Sep 2011

2. Simmons Creek

3. A’
RYAN
0 5 km
Y
AR
UND
BO
NT
ME
CH
CAT
ALMA
PARK
MULLEMBLAH
HILL
Larundel
Swamp
ons Creek
MOUNT
ROYAL
Wiesners
Swamp
Simm
ek N
Cre CA
IR
ns UL
mmo To
C
Si
WALBUNDRIE
A Billa
bon
g Cr e MORGANS
ek LOOKOUT

4. 17,700 ha
35 farms
500 ha av size
9,000 t/yr salt load

5. Land use
Area (ha)
10000
7500
5000
2500
0
Low Med High Native Improved
Rotations Pasture Trees

6. Hydrology & water balance

7. Sub-catchments
2
1
4
3
5
6
11
8 7
10
12
9
13

8. Groundwater
Sub- Salininty
Catchment (mS/cm)
2 10 25,000
1
11 24,000
4
3 8 20,000
5 7 15,000
6
12 10,000
11
6 10,000
8 7
10
9 2,000
12
9 13 1,000
13

9. Change land use to reduce salt load
 How much and where?
 What?
 Is there a cost?

10. Estimating the water balance
APSIM (APSRU)
Simulations on each land unit
Plant biomass/yield
Plant water use & evaporation
Vertical & lateral flow of water
FLUSH (CSIRO L&W)
Water movement across land units
Water flow into channels

11. Agricultural Economics & Hydrology
Gross Margin
($ ha-1 y-1)
400
Gross Margin
($/yr) 300
200
100
Drainage
(mm yr-1)
0
100 Low Lucerne Pasture Lucerne Pasture Native Im proved
Medium Medium High High
Drainage 75 Rotation Pasture Trees
(mm/yr)
50
25
Run Off
0
(mm yr-1)
75 Low Lucerne Pasture Lucerne Pasture Native Improved
Medium Medium High High
Rotation Pasture Trees
Runoff
50
(mm/yr)
25
0
Low Lucerne Pasture Lucerne Pasture Native Improved
Medium Medium High High
Rotation Pasture Trees

12. Estimating Salt Delivery
 Linear Program
– Specified salt load @ Max GM
 Inputs
– Gross margin
– Drainage
– Runoff

13. Amount of change
12000
10000
Land Use Changed (ha)
8000
6000
4000
2000
0
9000 8000 7000 6000 5000 4000 3000 2000 1000
Salt Load (t)

14. Amount of change: sub-catchments
100%
10
75%
Land Use Changed
8
50% 7 2
9
4
13
25%
12 6
0%
9000 8000 7000 6000 5000 4000 3000 2000 1000
Salt Load (t)

15. 2
1
4
3
5
6
11
8 7
10
12
9
13

16. What to change

17. Cost
3
Farm income ($M/yr)
2
1
0
9000 7000 5000 3000 1000
Salt load (t)

18. Cost: sub-catchments

19. Will these changes happen?
 Probably not
– Wicked problem
– Inequity
– High cost

20. What did we learn?
 Policy tool to assess ES
 Scale matters
 Rural Social Research not an ‘add on’

22. Thanks
Simmons Creek Community
(Bernie Coyle, Hamish Ellis, Leon Kolhagen, Peter Wallis)
Murray CMA