This presentation demonstrates how geospatial tools like high resolution digital elevation models and GIS techniques can be used to identify critical nutrient source areas and target agricultural best management practices. It describes a project in the Grand River watershed that developed a DEM and used terrain analysis and the RUSLE model to map priority areas for gully and sheet erosion. These maps can help extension programs better target outreach and financial incentives to farmers in high risk locations. Initial results show this approach increased requests for technical assistance and requests for mapping in new areas. Future applications include identifying priority subwatersheds and connecting issues to appropriate BMPs.

1. 1
Using Geospatial Tools to Identify
Critical Nutrient Source Areas and
Agricultural BMP Implementation
Priorities
Presentation by: Louise Heyming
Grand River Conservation Authority
Cambridge, Ontario, Canada

2. 2
Project Objectives
1) Demonstrate how a high resolution digital
elevation model (DEM) and advanced GIS
techniques can be used to determine nutrient
source areas
2) Demonstrate how the identified nutrient
source areas can be used to target agricultural
best management practices (BMPs)

3. 3
The Grand River Watershed

4. 4
80 year history of water
management planning
Shared responsibility
Successful collaboration
Building on existing data,
knowledge and
accomplishments
Finding practical ‘best
value’ solutions
A long history of water management
2014

5. 5
Water Management Plan Goals
Ensure sustainable water supplies
for communities, economies
and ecosystems
Improve water quality to improve
river health and reduce the river’s
impact on Lake Erie
Reduce flood damage potential
Increase resiliency
to deal with climate change

6. 6
Phosphorus Loads
Priority watersheds were
identified through the
Water Management Plan
Highest P
concentrations occur
during spring from non-
point sources
Point sources dominate
in summer
(Adapted from GRCA 2006)

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Identifying Nutrient Source Areas
Terrain Analysis Approach
Gully Erosion
RUSLE-FAC Approach
Sheet Erosion
Identify Priority Areas Identify Priority Areas
High Priority Areas for BMPs

8. 8
Pilot Study Area – Firella Creek
The Upper Nith River Sub-
basin was identified as a
significant contributor of
nutrients and sediment in
the Water Management
Plan
 Firella Creek study
area covers
approximately 32
km2 and is located
within the Upper Nith
Sub-basin
Lake Erie

9. 9
DEM Development
Stereo Project Creation:
Aerial Data
 Scans
 Camera Files
 Orientation Files
 Control Files

10. 10
DEM Development
Source: www.planar3d.com
Large Scale 3D
Vector Hydrology
Creation:

11. 11
DEM Development
Pixel-Auto Correlation (PAC) Point Collection:

12. 12
Final Firella Creek DEM

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Terrain Analysis Approach
Digital Elevation Model
Slope Raster
Stream Power Index Raster
Flow Accumulation Raster
Stream Power Index
measures the erosive power
of flowing water, identifies
areas of potential gully
erosion
Approach adapted from (Galzki, Birr and Mulla 2011)

14. 14
Terrain Analysis Approach
Stream Power Index (SPI)
High SPI values
represent the likely
overland flow paths
during a storm event
– the potential gullies

15. 15
Stream Power Index (SPI) Signatures
Terrain Analysis Approach
SPI Value Percentile
-0.540 75.00%
-0.079 80.00%
0.460 85.00%
1.135 90.00%
2.214 95.00%
A path of high SPI
values that flow into
observed surface
hydrology

16. 16
Terrain Analysis Approach
Field Verification
SPI Signatures - 95th Percentile
Correctly
Identified
Incorrect Identification
False Positive Thick Vegetation Other
9/10 (90%) 0/10 (0%) 1/10 (10%) 0/10 (0%)

17. 17
Terrain Analysis Approach
Stream Power Index
Signatures
Stream Power Index
Signature Catchment Areas

18. 18
Priority Areas using Terrain Analysis

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RUSLE - FAC Approach
A = R * K * L * S * C * P
Average annual soil loss – Potential sheet erosion
(tonnes/hectare/year)
RUSLE–FAC = Revised Universal Soil Loss Equation – For Application in Canada

20. 20
Priority Areas using RUSLE - FAC

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Priority Nutrient Source Areas
Priority Nutrient Source Areas - High Values
SPI – High Catchments
RUSLE-FAC -High Values

22. 22
Current Extension Program Approach
Technical assistance and
financial incentives to all
farmers
Work with those farmers who
come forward (i.e. they know
they have an erosion issue)
Financial incentives are
offered for both structures
and conservation practices
All erosion control projects
are offered the same incentive
structure
Photo: C. Heibert

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Mapping Objectives
Identify most vulnerable
areas
Apply BMPs best suited to
issue (gully and/or sheet
erosion)
Target outreach and
financial incentives
(location, incentive level)
Photo: A. Loeffler

24. 24
At the Farm Scale

25. 25
At the Farm Scale

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At the Farm Scale

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Early Results
Increase in requests
for technical
assistance to design
erosion control system
Requests for mapping
outside our pilot study
area
Photo: A. Loeffler

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Future Applications
Internal CA use:
 Identify priority subwatersheds (best value
solutions)
 Connect issues to BMPs (structures vs
cropping practices)
 Identify potential water quality monitoring
sites.
Communication tool:
 Engage landowners to raise awareness.
Program delivery level:
 Tailor financial incentives to improve
chances of target farms participating.
Erosion control structure design
 DEM will help facilitate design work
Photo: L Heyming

29. 29
Thank you
Ontario Ministry of the Environment & Climate Change
Grand River Conservation Authority
Ontario Ministry of Agriculture, Food & Rural Affairs
Regional Municipality of Waterloo
Agriculture & Agri-Food Canada
Environment Canada
This Project has received funding support from the Government of Ontario. Such support does not indicate endorsement by the Government of Ontario of the contents of this material.

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References
Galzki, J. C., et al. "Identifying critical agricultural areas with three-meter LiDAR elevation data
for precision conservation." Journal of Soil and Water Conservation 66.6 (2011): 423-430.