How we monitor
Waikato Regional Council obtains information on the number and type of stock on each farm in the Waikato region from the AgriBase database. AsureQuality New Zealand Ltd (formerly AgriQuality Ltd) developed, and now maintains, AgriBase.
We estimate the area of pastoral land on each farm from the Ministry for the Environment’s Land Cover Database4 < Land cover data supplied by Terralink NZ Limited. COPYRIGHT RESERVED.
Waikato Regional Council measures stock density across the Waikato region.
AsureQuality New Zealand Ltd maintains AgriBase records through:
- routine contact with farmers
- monthly updates of property changes from Quotable Value New Zealand.
Waikato Regional Council intends to purchase AgriBase every six months or as the need arises.
The Ministry for the Environment intends to update the LCDB every five years. Waikato Regional Council’s monitoring of pastoral area depends on the release of the updated LCDB by the Ministry for the Environment.
Development of the AgriBase system began in late 1988. National data capture began in 1993. Waikato Regional Council purchased a snapshot of the AgriBase database every six months since 2008.
The LCDB 4 data is primarily derived from SPOT 5 satellite imagery acquired between November 2011 and February 2013. More information is available from the dedicated Land Cover Database website.
Waikato Regional Council uses:
- AgriBase data on stock numbers to calculate the number of stock units on each farm and the land area of the farm.
- LCDB4 to calculate the area of pastoral land on each farm.
Waikato Regional Council calculates stock density for each farm by dividing the total stock units on the farm by the total area of pastoral land. Following this process for the whole region requires a series of steps, outlined below.
- Due to the way in which the AgriBase dataset is constructed, we first pre-process the data using GIS tools to avoid overestimating stocking rates. A 'flattening' process is used to area proportion AgriBase recorded stock numbers to the available LCDB 4 pastoral extent. This is necessary because AgriBase records the total area of each farm, which may include non-pastoral land.
- We work out the total stock units for each farm by converting the animals into common stock units (or ewe equivalents) and calculating a farm total. We use the Agribase stock data and the AgriQuality stock unit conversion factors for this task. We also use information from AsureQuality about the typical distribution of stock classes expected on a ‘standard’ farm. This allows us to estimate stock density in more detail for each farm type.
- We classify stock density on each farm into one of the five classes shown below.
Stock density classes
Stock density class (stock units/ha) Farm type where stock density class typically observed Cows per hectare equivalent Less than 10.5 Sheep farms Less than 1.5 10.5 to 17.5 Beef farms and lower stocked dairy farms 1.5 to 2.5 17.5 to 24.5 Mid-range of dairy farms 2.5 to 3.5 Greater than 24.5 Higher stocked dairy farms Greater than 3.5 Stock density not calculated Reliable data not available
- We identify which of theeight major water catchment zones in the Waikato region each farm fits into. This helps us determine how stock density might be affecting water quality in different parts of the region. For example, river water quality monitoring shows that water quality for ecological health is poorer in the Hauraki, Waipa, Lower Waikato and Middle Waikato water catchment zones, where stock density is highest.
- We calculate the number of farms in each stock density class for each water catchment zone.
- We create a map showing the distribution of stock density in the Region. We map each farm in one of the five stock density classes listed in Table 1.
For example, the total stock units for dairy stock were calculated using the following formula:
Dairy Stock Units = (0.731 x Dairy numbers x 7) + (0.245 x Dairy numbers x 4.25) + (0.024 x Dairy numbers x 5.5).
To calculate stock density from AgriBase data, Environment Waikato uses the AsureQuality stock unit conversion factors. These factors are used to work out feed budgets in the agricultural industry.
AgriBase data cannot be used to calculate farm-based stock densities for all farms in the Waikato Region. This is because not all land parcels in the database are linked to a specific farm.
The AgriBase data purchased by Environment Waikato does not discriminate between the age classes of the animals. The equation used to calculate total stock units is a generalised one that uses typical stock classes on farms.
Quality control procedures
For information on the Land Cover Database data quality (lineage, positional accuracy, attribute accuracy, logical consistency and completeness) see the updated metadata for the LCDB available from the dedicated website – Land Cover Database.
A number of sophisticated quality assurance procedures (including statistical, SQL query, visual/spatial inspection) have been developed by AgriQuality New Zealand Ltd to verify the incoming data for AgriBase.
1.The LCDB 4 dataset is a 'public good' dataset owned by the Ministry for the Environment and supplied under Creative Commons V4 licensing
Supplied by AsureQuality New Zealand Ltd.