Whats New #1

Whats New #1

Monday, June 20, 2016

The fresh water quality of New Zealand is considered very clean by international standards however in dense urban and rural areas the water quality has degraded. In NZ, diffuse pollution from agriculture is one of the main sources of water contamination of fresh waters. Subsequently, a balancing act is required by government to help preserve local water bodies as a high quality resource, while enabling primary industry to continue with increased productivity for a better economy. A National Policy Statement for Freshwater Management (NPS-FM) was introduced by the government in 2011 that requires each region to maintain or improve the quality of freshwater. This policy was amended in 2014, which put the onus on regional councils to account for all water takes and sources of contaminants.

Otago regional council Water quality Plan change 6A

In response to the NPS-FM the Otago regional council made changes to the existing regional plan for water, designated Plan Change 6A, which outlines the water quality rules for the Otago region. The ORC rules are an effects-based, permitted activity approach and puts the responsibility onto farm management to maintain water quality on farm.

The ORC has introduced Schedule 15 and 16 as part of Plan Change 6A to address NPS-FM statement regarding maintaining good water quality and improving poor water quality. Schedule 15 measures the health of the freshwater in the Otago region by describing the characteristics and contaminant limits that are the target for good quality water (see appendix 8.2 for Schedule 15 limits). The ORC aim to meet these limits for all receiving water bodies by 31 March 2025.

Schedule 16 covers discharge thresholds for contaminants that leave the farm and enter a waterway. Surface water discharge from drains and races and groundwater seepage into receiving waters are a permitted activity under schedule 16 as long as they comply with the threshold limits for nitrogen phosphorus and E. coli by 2020 (see appendix 8.3 for Schedule 16 thresholds). These thresholds apply only when the representative flow site (Taieri River) is at or below median flow of 15.86 cumecs (see site http://water.orc.govt.nz/WaterInfo/Site.aspx?s=Outram for Taieri River flow information). Stock access to waterways is considered a permitted activity provided some conditions are met for example, no noticeable slumping, pugging or erosion to the stream bank and no visual change to colour or clarity of water (visit ORC website for full conditions).

Figure 2‑1 Contaminants from a catchment and deer wallows on the Invermay farm

The results are shown for all contaminants sampled within the Invermay catchment A site during base flow <0.2 L s-1 (0.0002 cumecs) and storm flow ≤ 30L s-1 (0.3 cumecs). Concentrations are shown as box (25th and 75th percentile, median) and whisker (5th and 95th percentile, outliers as filled circles) plots indicate the relative concentration The wallow data shown is the combined results of water sampled from 32 ephemeral waterways that flowed from wallows to permanent streams within Invermay deer farm during storm events. Data collected for 1 year from Aug 2004.

As from 2014, the sediment management rules were applicable to all farms. Sediment mitigation must be in place when land is disturbed in proximity to a waterway, such as during ploughing and forage crop grazing. Discharge of sediment into water from disturbed land is a prohibited activity under Plan change 6A rules (as from 2014). Further prohibited activities also include gross discharge into waterways of dairy effluent and silage runoff, both of these contaminants must be contained.

Water quality on the Invermay farm

Plan Change 6A affects the Invermay farm in its current state due to risk of non-compliance. The main issue being sediment loss to water with the main cause from deer access to waterways. Research investigating the environmental consequences from deer accessing waterways has been performed in the past on the Invermay deer farm. The study area was a waterway on the Invermay farm (Map 2-1 - monitoring flumes) that is generated from seeps within paddocks Tank and Low Burma flowing down to monitoring flumes in paddocks 153 and 155. This work demonstrated the negative impact deer have on water quality by monitoring the contaminant losses from a wallows within or nearby waterways (7.2.1). Continued research also showed the benefit of fencing off deer access to wallows situated in close proximity to waterways as a successful mitigation method (7.2.2)

The impact of deer on water quality 

The use of safe wallows to improve water quality

Figure 2‑2 Fencing deer from water improves water quality

Results show contaminant concentrations in water samples collected for the first 2 years before fencing and planting riparian plants and the following 2 years after. Concentrations are shown as box (25th and 75th percentile, median) and whisker (10th and 90th percentile, outliers as filled circles) plots indicate the relative concentration before and after fencing and planting. Asterisks indicate statistical significance between the mean concentration before and after planting.

Water sampling has continued at the monitoring flumes beyond the publication of this work. The water sampling results are shown along with Schedule 16 discharge thresholds (Figure 7-3, thresholds shown as a green line).

Current contamination levels of a single waterway on Invermay farm

Figure 2‑3 Current contamination levels from a single waterway on the Invermay farm

Graphs in figure 7-3 show the levels of E. coli, dissolved reactive phosphorus and nitrate measured over time on the Invermay farm from water samples collected from a single waterway. Note nitrates have not been measured on the same time scale as the other contaminants.

This research highlights the importance of excluding deer from waterways to improve water quality. However, the current contamination results shown in Figure 7-3 also indicates that E. coli thresholds set by the ORC in Schedule 16 may be difficult to meet even after our waterways are fenced. 

Based on the visual condition of the Invermay farm waterways, turbidity caused by prolonged sediment loss into waterways will also be problematic for meeting the ORC limits for good water quality (Schedule 15).

Monitoring programme

The main focus of the monitoring programme will be on water quality to ensure the Invermay farm meets compliance limits. The minimal amount of monitoring required to determine water quality on the Invermay farm is suggested in the table below (Table 7-2), which will be a farm cost.

There are four main waterways that exit the Invermay research campus (Map 2-1) and enter the Silverstream. These sites should be the initial monitoring sites for determining the water quality leaving the Invermay farm.

Both Farm Systems and Land & Environment based at Invermay will share any research related costs required for monitoring the success of various projects around mitigation strategies that have been implemented on the Invermay farm over the course of the five year plan.

Biodiversity is an indicator of stream health and high sediment levels are known to smother aquatic life. There was very little biodiversity identified by the ORC electric fishing team on the Invemay farm (15/9/2014). The Invermay farm plan addresses these problematic erosion areas within the farm to prevent further sediment loss into the farm waterways. Therefore, biodiversity monitoring should be continued as a measure of improved stream health.