Nitrogen Discharge to Lake Taupo in TDC Wastewater: October 2025 Update

Taupo District Council’s contributions to Lake Taupo Protection include management of numerous wastewater treatment plants to control nitrogen discharge. In 2006, a nitrogen discharge was set for the eight treatment plants in the Lake Taupo catchment (Figure 1, as presented to LWAG in August 2025 by Michael Cordell, Taupo District Council). Note that Taupo town’s treatment plant is not one of these eight; Taupo’s treated wastewater goes outside the catchment to Rakanui Road and View Road.

Figure 1: Nitrogen discharge from TDC wastewater treatment plants in the Lake Taupo catchment and the discharge limit (Mike Cordell, Taupo District Council, August 2025).  

The nitrogen discharge limit was set after calculating the sum of discharge from the plants to 2006 (Bou et al., 2006), and the limit which is a 20% reduction of the sum. This limit is displayed as the horizontal ochre line on Figure 1.

A few takeaway points from the chart and some context:

  • The sum of annual discharge is generally less than the limit, which is good.

  • Last year (2025) was the lowest on record, which is particularly good for wastewater treatment.

  • Waitahanui wastewater was removed from the chart in 2018. This happened as TDC began treating this wastewater in the Taupo plant, and is a win for Lake Taupo water quality.

  • Turangi wastewater treatment plant (shown in green) produces the most nitrogen outflow to Lake Taupo. This outflow seems to be the biggest risk to attainment of the nitrogen discharge limit.

All-in-all, a good result for the lake since 2006 has come from TDC’s excellent efforts on wastewater treatment. For more context about this chart, please check out the full presentation recording here from the most recent LWAG meeting. The discussion relevant to this chart begins around 28:56 in the video.

Reference:

Bou, A. Church, N, White, P.A.  2006. Nutrient discharges from Taupo District Council wastewater treatment plants in the Lake Taupo catchment.  GNS Client report 2006/76.

The above content was written by Paul White and edited by Joshua Sargent.

Taupō Lakes and Waterwayswastewater, TDC