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

ulat

ed to

tal p

hosp

horu

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

ulat

ed to

tal n

itrog

en (t

)

Observed total nitrogen (t)

Nitrogen Loads (kg/yr)

Hands-on SessionRun the water yield model

Hands-on SessionRun the nutrient retention model

Hands-on SessionRun 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 𝑇𝑜𝑡 𝑟𝑒𝑡𝑎𝑖𝑛𝑥∗𝑀𝐶(1+𝑟 )𝑡

forestStream

Pollutant input

Ywheat

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(**)(_CNLLoadAnnretainedpCostValuewp xx