8. Risk
of Loss
= Source X
Dominant
Transport Pathway
=
Source
X
Transport Pathway
NAHARP
Model Surrogate
NAHARP Model Component
PP = Soil P X
Water erosion
towards surface water
=
Cumulative P*
(kg P/ha) IROWC‐P
X
Inherent erodibility of soil
(k*L*S) WatERI
DRP = Soil P X
Runoff
towards surface water
=
Cumulative P*
( kg P/ha) IROWC‐P
X
Surface runoff (R, mm)§
IROWC‐P VSMB
Soil = Soil X
Water erosion
towards surface water
=
k (erodibility of soil)
WatERI
X
L*S (length, slope of landscape)
WatERI
NO3
‐ = Soil N X
Leaching
through soil
=
Average§ N‐balance
(kg N/ha) RSN
X
Deep drainage (D, mm)§
IROWC‐P VSMB
Soil = Soil X
Water erosion
towards surface water
= Average§ WatERI (t soil/ha/year)
Our approach
• Risk determined for each SLC in the watershed
* Because P is conserved from year to year a cumulative P parameter for 2006 was developed by linear interpolation of the P‐
balance values of each of the six Census years (1981‐2006)
§ Average value of each of the six Census year data (1981‐2006)
27. Citations:
Eilers, W., R. MacKay, L. Graham and A. Lefebvre (eds). 2010. Environmental Sustainability of Canadian Agriculture: Agri‐Environmental
Indicator Report Series — Report #3. Agriculture and Agri‐Food Canada, Ottawa, Ontario.
• Drury, C.F., J. Yang, R. De Jong, T. Huffman, X. Yang, K. Reid and C.A. Campbell. 2010. Residual Soil Nitrogen. Pages 74 – 80 in Eilers, W., R.
MacKay, L. Graham and A. Lefebvre (eds). 2010.
• Lobb, D.A., S. Li and B.G. McConkey. 2010. Soil Erosion Risk (integration the risks of wind, water and tillage erosion). Pages 46 – 53 in
Eilers, W., R. MacKay, L. Graham and A. Lefebvre (eds). 2010.
• McConkey, S. Li, M.W. Black and D.A. Lobb. 2010. Water Erosion Risk Indicator. Page 48 in Eilers, W., R. MacKay, L. Graham and A.
Lefebvre (eds). 2010.
• van Bochove, E., G. Thériault, J.‐T. Denault, F. Dechmi, A.N Rousseau and S.E. Allaire. 2010. Risk of Water Contamination by Phosphorus.
Pages 87 – 93 in Eilers, W., R. MacKay, L. Graham and A. Lefebvre (eds). 2010.
Li., S., B.G. McConkey, M.W. Black and D.A. Lobb. 2008. Water Erosion Risk Indicator (WatERI) Methodology in Soil erosion risk indicators,
Technical Supplement. Ottawa, ON, Canada:Agriculture and Agri‐Food Canada
van Bochove, E. and J.‐T. Denault (editors). 2009. Indicator of Risk of Water Contamination by Phosphorus (IROWC‐P). A Handbook for
presenting the IROWC‐P Algorithms. Research Branch. Agriculture and Agri‐Food Canada. Quebec. Contribution No. AAFC/AAC, 94 pp.