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Invest 2.2.1Nutrient Retention model
Yonas Ghile
Why Nutrient Retention model?
~ 14,000 people die daily
Global water treatment cost
~$24.6 billion/year
Dead fish zone in the Gulf of
Mexico ~5, 000 mil2
Non-Point Source is major cause
Biophysical Inputs
Land Use/Land CoverNutrient loading, Retention capacity, root depth, crop coefficient
TopographyDigital elevation model, slope threshold
ClimatePrecp, PET
SoilsSoil depth, PAWC
Watershed AreasMain and sub for point of interest and water quality analysis
Biophysical Inputs...
1. Estimate Water yield 3. Estimate Pollutant Load value
4. Estimate nutrient retained
5. Estimate pollutant reached the stream
𝐴𝐿𝑉 𝑥=𝐿𝑉 𝑥∗ 𝐴𝑥
𝑅𝑒𝑡𝑥=𝐴𝐿𝑉 𝑥∗𝑅𝑥
wheat
Cornforest
2. Calculate flow direction
Valuation
Time
Load
ing
Critical Loading
6. Estimate Avoided treatment costs
Some Questions
Where are the pollutant sources?
Where are the pollutant retention areas?
How much is retained?
What is the Value of this retention?
Informs Policy Makers to
Protect areas that retain most
Design management practices that lead to maximum retention
Create payment programs to get most return on investment
Identify services that conflict with water purification
How much retention will we gain or lose under future
management or conservation plans?
Strengths
Uses readily available and minimum data
Simple, applicable and spatially explicit
Link the biophysical functions to economic values
Values each parcel on the landscape
Limitations All bio-physio-chemical processes are lumped in one number
export coefficient
Annual basis, misses seasonality
No instream processes and point sources
Less relevant to areas dominated by infiltration excess
Assess one pollutant per run
No saturation in uptake
Model Calibration and Testing
Sensitivity Analysis to identify most sensitive parameters
Model Calibration using long term average actual data
Find crop coefficient and root depth within acceptable ranges
Model parameter (Zhang constant)
Find export coefficients and vegetation efficiencies within
acceptable ranges
Validate Model by conducting comparisons with observed data or
other model output
y = 0.81xR² = 0.94p < 0.01
0
100
200
300
400
500
600
0 100 200 300 400 500 600 700
Sim
ula
ted
to
tal p
ho
sph
oru
s (t
)
Observed total phosphorus (t)
Phosphorus loads (kg/yr)
Hainan Island, China
Hainan Island, China
y = 1.11xR² = 0.92p < 0.01
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000
Sim
ula
ted
to
tal n
itro
gen
(t)
Observed total nitrogen (t)
Nitrogen Loads (kg/yr)
Hands-on Session
Run the water yield model
Hands-on Session
Run the nutrient retention model
Hands-on Session
Run the valuation model
Hainan Island, China
Actual (2008)
IEM RNF
No Expansion
IncreaseNo changeDecline
Baoxing, China
Retained TN Retained TP
High
Low
High
Low
Scenarios for Mine Expansionin Columbia
Current Mines
Permits Granted
Permits Pending
All possible permits
Columbia
Permits Granted Permits Pending All possible Permits
Change in Nitrogen Export (kg/ha/yr)
Columbia
High Impact Zones should avoided
Permits Granted Permits Pending All possible Permits
Coming up soon
Improve vegetation retention rates
Include Point source pollutant
Include bacterial contamination
Improve pollutant load adjustment
Tier 2 nutrient retention model
Hands-on Session
Any idea how you would use the Nutrient Retention Model in your work?
How Does it Work?
• Pollutant Load Value:
• Hydrologic Sensitivity Score:
• Adjusted Loading Value:
𝐿𝑉 𝑥=𝐸𝑥∗𝐴𝑥
= =log
*
How Does it Work?...
𝑃𝑉𝑆𝑅𝑥=∑𝑡=0
𝑇−1 𝑇𝑜𝑡𝑟𝑒𝑡𝑎𝑖𝑛𝑥∗𝑀𝐶
(1+𝑟 )𝑡
forest
Stream
Pollutant input
Y
wheat
Cornforest
How Does it Work?...Removal of polluntats by vegetation and soil along the flowpaths is calculated as follows
Valuation
Time
Load
ing
Critical Loading
)_
1(**)(_CNL
LoadAnnretainedpCostValuewp xx