Current Freshwater State

Recreational water quality monitoring

The three recreational water quality monitoring sites in this FMU produce results at opposite ends of the spectrum in the most recent 2022/2023 report, in line with previous years. As has been observed in previous seasons, the lowest E. coli concentrations were measured at the Pelorus Bridge, while the Rai Falls registered the highest bacteria levels. The elevated E. coli concentrations in the Rai River result in higher levels at Totara Flat, located downstream of the confluence of the Te Hoiere/Pelorus and Rai Rivers.

The Suitability for Recreation Grade (SFR) for the Te Hoiere/Pelorus River at Pelorus Bridge has remained 'Good' for a decade, making it the river site with the region's best recreational water quality. In contrast, Totara Flat and Rai Falls each hold an SFR Grade of 'Poor'. Trend analysis reveals little change in E. coli concentrations at the two Te Hoiere/Pelorus River sites, but a noticeable increase at Rai Falls over the last 10 years.

Similarly, the 2021/2022 report states that the Pelorus River site at the Pelorus Bridge has the best water quality of all the sites monitored and an NPS-FM state of “Good”. In contrast, downstream in the same river at Totara Flat, the NPS-FM state is “Poor”. Unfortunately, the third site on the Rai River at Rai Falls had not been re-operational for long enough to provide sufficient data for a grading. However, the testing indicated that the site will most likely be graded “Poor” too, due to the site having the poorest water quality samples of all eight sites across 2021/2022.

Groundwater quality

There is one groundwater quality monitoring well at “10323 Rai Valley” in this FMU. The five-year median monitoring result is shown below:

Records at the monitoring well so far record the following information and trends to April 2023:

• The annual seasonal variation in stage (level of water in the well) is normally 1 metre but can be up to 1.5 metres in some years.
• Interestingly, there were virtually no E. Coli microbes present in the groundwater at this well despite an underlying intensive land use and high E. Coli at the Rai Falls surface water monitoring site.
• High magnesium and iron concentrations in the groundwater at this well compared to the rest of the SOE groundwater monitoring network are in part due to the mineral belt which naturally occurs in the western side of the catchment.

Municipal supply

The most significant urban water use is Havelock municipal water supply. This is a reticulated, council owned scheme servicing residential properties in the township. It is supplied from two bores adjacent to the Kaituna River. Chlorine is added to the water at the pump station, then the water is pumped to a new steel service reservoir, built in 2010.

Water quantity and use

In June 2023, the Te Hoiere/Pelorus FMU rivers (Rai, Pelorus, and Kaituna) all had mean flows around 50% of their long-term means. This was predominantly due to low rainfall during the month. All three rivers have significant flow records dating back to the 1970s-80s, so their long term mean flows are well established.

Individual Resource Consents

Generally, this FMU is considerably less irrigated than the Wairau plain and is predominantly dairy farm platform irrigation and accordingly a lower quantity of water is used for this purpose. There are considerably fewer water take resource consents than the Awatere or Wairau FMU despite the larger amount of surface water available.

The number of water take Resource Consents (RC) in this FMU are shown in the table below. An additional 5 water take RCs exist in the Wakamarina area which is not included on the Appendix 6 allocation table. The numbers are correct as at October 2023.

With the lack of significant groundwater aquifers in Te Hoiere/Pelorus, water abstractions come directly from rivers or shallow wells and infiltration galleries alongside the river. Water takes are controlled by MDC and daily allocation limits placed on municipal water supplies as well as other takes. Where allocations are not specified, controls are placed on takes relating to the river’s mean flow levels. There are also cut off levels for different classes of takes. This is shown in the table below.

As discussed above, irrigation water is classed with different rationing and cut off flows for each class. C class is taken for placing into water storage, generally during periods of high flow – as shown by the higher rationing and restriction flow cut offs. When the flow levels are recorded as falling below the rationing or restriction amounts, associated steps are taken by water users to comply with this management.