Stock access to waterways

Randomly selected 500 m lengths of waterway from all pastoral land were selected for the monitoring. The sites are stratified by management zones, land use, and waterway size (as measured by Strahler stream order).

The monitoring occurs every five years.

The regional riparian characteristics survey was completed for the first time in 2002 and has been repeated in 2007, 2012 and 2017.

The regional riparian characteristics survey employs a sampling approach to provide scientifically robust estimates of the state of observed riparian characteristics (e.g. the proportion of bank length fenced). A sample site is an approximately 500 m long stretch of waterway in pastoral land at which the riparian characteristics (such as fencing, vegetation, and stream-bank erosion) are observed along both banks. Sites and observations are spatially referenced by GPS and the data are recorded using hand-held computers.

The raw data is stored in Excel spreadsheets and saved in Waikato Regional Council’s electronic document management system. The GPS data is stored in GIS layers.

The length of each sample site (approximately 500 m) is walked, adjacent to the waterway, and the riparian characteristics on both banks are observed and the data captured using a hand-held computer with built-in GPS. Changes in characteristics from those observed at the start point are recorded together with the spatial location of the change. The resulting stream segment information allows for the length and proportion of total stream length or bank length with certain characteristics (e.g. effective fencing) to be calculated. Data were collected at 432 sample sites across the region during the 2017 survey.

Proportions of bank and stream length (with associated confidence intervals) were calculated, categories compared, variables correlated, and change over time determined using appropriate statistical analysis techniques. All analyses were carried out using purpose-built procedures written in R.

Survey results in terms of the state and trend in riparian characteristics are presented for the region as a whole (i.e. region-wide), by management zone, land use (dairy and drystock), and stream order (a representation of stream size). Proportions of bank length have been presented here as graphs.

The raw data are collected using hand held computers with built-in GPS and transferred to Excel spreadsheets. The data held in Excel spreadsheets are imported into specialised statistical analysis software (e.g. R) for analysis. The data have been saved in GIS and Excel files stored in Waikato Regional Council’s electronic document management system.

There are no technical documents showing how the indicator data is quality assured but calibration of field observations and checking procedures for data accuracy is built into the methodology.

This indicator is not an actual measure of stock access to streams at every length of stream. It is a stream length sample method that provides estimates for management zones and the region as a whole. Assumptions are made about fencing and how effectively it prevents stock access. The absence of a fence has been assumed as allowing stock access.

The average proportion of bank length fenced across the Waikato region has significantly increased over the past fifteen years from 28% in 2002 to 61% in 2017. The rate of increase in the amount of fencing over the 2002-2017 period has been about 2.2 per cent of bank length per year. Fencing here is defined as ‘effective’, that is a structure which completely excludes stock stock access to the waterway and is adjacent to the riparian margin.

There are clear differences in the amount and configuration of effective riparian fencing between dairy and drystock land uses and in 2017, the average proportion of bank length effectively fenced was significantly greater for dairy (87%) compared to drystock (36%). Over the past fifteen years, the proportion of bank length effectively fenced has significantly increased from 44% in 2002 to 87% in 2017 for dairy and from 19% in 2002 to 36% in 2017 for drystock. With regards to the preceding 5-year (2012 – 2017) and 10-year (2007 – 2017) periods, the proportion of bank length effectively fenced has significantly increased for dairy but not for drystock. The rate of fencing change over the entire fifteen-year monitoring period was about 3.1% of bank length per year for dairy and about 1.3% of bank length per year for drystock.

The change in the amount of fencing (as a proportion of bank length) for each management zone over the 2002 – 2017 period is shown in the graph below. In 2017, the Waihou Piako zone had the highest average proportion of bank length effectively fenced (84%) with the lowest proportion present in the West Coast management zone (28%).

Significant increases in the percentage of bank length effectively fenced (2002 – 2017) were observed in all except the Lake Taupo management zone, where the proportion of bank length effectively fenced in 2002 was relatively high (59%). Over the last five years, significant increases were restricted to the Coromandel and Waihou Piako zones.