Paper 640
Steve Abbors, EBMUD Project Manager, Reza Ghezelbash and Mardi Jackson, GIS Consulting &
Application Development.
Title: Using GIS Applications to Improve Management of Cattle Grazing Allotments
in Central Coastal California.
Defining Issue: EBMUD resource managers needed a tool to predict the optimum number of
cattle (stocking rate) that could be permitted to graze watershed area where soil type, slope and aspect vary
by location and rainfall varies temporally. The predictive model would be used to protect the main agency
goals of water quality and biodiversity by helping to adjust stocking rates to minimize resource damage
from grazing as conditions vary.
GIS Solution: Develop an overlay coverage based on slope, soil, range site, production,
Residual Dry Matter (RDM) requirements, rainfall and sensitive habitats to determine stocking rates. Use
spatial change detection (temporal GIS) to monitor effects of different grazing regimes.
Application: This application allows resource managers to determine stocking rates for grazing
leases via ArcView and ArcInfo. It also allows the user to view and query other layers significant to
management goals such as: fire risk and sensitive species.
Software: The range site analysis model was built in ArcInfo using (AML and AWK) to
dynamically output analysis and queries in both ArcView and ArcInfo. The program is designed to
maintain the native look of an Esri command line function and allows the user to submit a rquest file
which includes all the input parameters. The purpose of this paper is to demonstrate the use of GIS in
range and watershed management.
CALCULATE AUM
{fence_identification_code}
The East Bay Municipal Water District (EBMUD) owns and manages approximately 28,000 acres of land
and water surface in the East Bay area. A geographic information system (GIS) was developed to provide
managers with information to help assess constraints and identify assets or opportunities needed to
implement resource management programs. The GIS inventory data set contains information regarding:
water quality, biodiversity, forestry, livestock grazing, fire and fuels, recreation and trails, cultural
resources and land ownership. The range management analysis application was created to assist in
preparing annual grazing plans for each lease area to ensure that grazing practices are consistent with
EBMUD's resource management goals.
The grazing plans specify annual stocking rates, required management actions and monitoring to evaluate
adherence to lease conditions. In developing the criteria to determine stocking rates the following
variables were considered:
1. Residual Dry Matter Requirements (RDM)--this is a range management term referring to the amount of
dry vegetation left at the end of a grazing season and is expressed in pounds per acre.
2. Slope-this variable was categorized into <5%, 5-35% and >35% slopes. Important in curbing erosion,
each slope category received it's own RDM requirement. Steeper slopes require more grass to remain
stable and so require a higher RDM.
3. Rainfall Classification--this variable was categorized into favorable, normal and unfavorable rainfall
conditions based on local conditions.
4. Soil Series-this variable was used to determine a production rate. The production rate is published by
the soil conservation service and predicts how much grass will grow in a given year. It is determined by
soil series and rainfall classification.
5. Pasture Area-this variable is a polygon bounded by fence lines and is defined in acres.
Stocking rates were determined by the following calculations and expressed in animal unit months
(AUM's) and pounds/acre:
Production - RDM (slope dependent) = Available Forage (pounds/acre)
Available Forage/ 800 (pounds/acre/cow) = Animal Unit Month (AUM)
AUM * Grazing Duration * Pasture Acreage = Stocking Rate
A composite coverage consisting of soils, vegetation, slope and pastures was developed to interface
with the CALCULATEAUM application and with ArcView. The user can access the yearly stocking rates
in two ways:
1. Via ArcView, the user can query individual pastures for acreage, available forage and stocking rates by
rainfall classification.
2. Via ArcInfo through sub-environments, the user can enter the command line function
CALCULATEAUM for a selection of pastures. CALCULATEAUM was written in
AML code to undertake the calculation and generation of an output coverages. The function returns a
summary of acreage, available forage and stocking rates by rainfall classification.
In the future a production region modeling tool specific to the East Bay Watershed can be developed. This
would incorporate regional weather data and actual grass production data instead of relying on the soil
conservation service production rates. By gathering many years of data it may be possible to predict
production and a from this, calculate stocking rates. Additionally, the regional model will be able to
compensate for regionally high or low grass production.
Contacts:
Steve Abbors, EBMUD Project Manager
Reza Ghezelbash, GIS Consulting & Application Development
Mardi Jackson, EBMUD
500 San Pablo Dam Road
Orinda, CA 94563
(510) 287-0459