Catchment Significant Pressures Description:
The significant pressures identified by the EPA during initial characterisation were Forestry, Domestic Waste Water Treatment Systems (DWWTPS) and Section 4 Discharge licences. The Unshin_050 has a High Status Objective, is a Blue Dot Catchment and forms part of the Unshin Special Area of Conservation (SAC). The biological Q score at the monitoring point dropped to Good in 2015, returned to High in 2018, dropped again to Good in 2019 and returned to High in 2020. This is a Protect referral to help reduce the impact of future forestry operations to water quality. Measures to reduce the impact from forestry are required.
Referral Significant Issue (s) Description
Phosphate is identified as the significant issue contributing to the decline in biological status of the Unshin_050. Sediment is also likely to be a contributing factor although the river has naturally occuring sediment (moderate – extensive) due to the nature of the bank margins, substrate and low elevation. Forestry activities are likely to further increase the levels of sediment load in the river.
Much of the forestry in the PAA was planted before 1990 i.e. before the introduction of Forest Service guidelines regarding buffer zone management along watercourses e.g. introduction of buffer zones, management of ground preparation and other forest operations to protect water quality, and therefore forestry poses a risk to water quality.
This referral is for minimising water quality impacts from future forestry operations in the Unshin_050. No deterioration is a requirement for High status Blue Dot sites. Therefore, protection measures will need to be put in place. A precautionary approach should be taken, and an effort should be made to minimise the risk from nutrients and sediment to the watercourse.
Example measures are proposed below.