Waitepuia Catchment

Land use in the catchment is predominantly dairy farming, accounting for over 50%. Horticulture (mostly kiwifruit) is the second largest land use type accounting for more than 30%. The Land Use Capability (LUC) is made up of a mixture of Class 2s (soil limitation), Class 3w (wetness limitation) and Class 3e (erosion limitation) land.

The soils comprising the lower elevation undulating land are gley soil. Gley soils exhibit high water tables in winter and impaired drainage, and are susceptible to flooding (Rijkse & Guinto, 2010). This is managed through drainage systems throughout the catchment. The other, less extensive soil types in the catchment include composite yellow-brown pumice soil on yellow-brown loam. These soils are well drained and volcanic in origin with parent materials coming from Kaharoa Ash, Taupō Pumice and more recent Tarawera Ash, making them versatile soils.

The lower Kaituna Plains (which includes parts of the Waitepuia catchment) were typical of most lowland areas and had natural wetlands (the largest wetland known as the Kawa Swamp ~ 6500ha), streams and large rivers. The majority of wetlands in this sub-catchment have been lost due to land drainage and agricultural development within the Lower Kaituna Wildlife Management Area (LKWMA). Some remnant wetlands of the once vast Kawa Swamp still remain, including Te Pourepo o Kaituna Wetland (in Ford Rd sub-catchment) and Whakapoukorero Wetland (in Waitepuia sub-catchment).

Small lateral drains were dug throughout the Kaituna Plains to help drain the waterlogged soil and allow agricultural development. This had the effect of converting lowland swamps into a series of modified stream channels. Of the 270km of waterways that flow in this area only about 20 km are relatively unmodified which have been contained between large stop banks to minimise flooding. The remaining waterways have been highly modified and straightened to drains.

The Kaituna Drainage Scheme has roughly 30-35kms of canals and drains and three pump stations in this sub-catchment, which are used to reduce flood impacts for low-lying landowners who pay a targeted rate within this scheme area.

Elevated levels of E. coli bacteria, nitrate-nitrite-nitrogen, total nitrogen and total suspended solids have been identified as the primary water quality issues within the Waitepuia catchment.

These elevated levels of contaminants move into the sensitive receiving environment of the Te Awa o Ngatoroirangi/ Maketū Estuary and may result in unsafe conditions for recreational contact, and impact estuarine health and freshwater wildlife.

Water quality in the Maketū Estuary has already been impacted adversely due to elevated nutrient levels nitrogen (N) and phosphorus (P) and bacterial levels (E.coli) (Park, unpublished (a) and (b)).

Bay of Plenty Regional Council scientists have estimated that to restore the estuary to moderate ecological health, improve safety for shellfish gathering and contact recreation, contaminants will need to be substantially reduced across the catchments that supply water to the estuary.

Past monitoring summary

Surface water quality monitoring

Water quality monitoring was carried out at six sites in the Waitepuia sub-catchment in November 2016 and 2017 as part of a general survey which covered 112 sites in the Kaituna Water Management Area (WMA). This one-off sampling indicated elevated total nitrogen and E. coli bacteria across the sub-catchment, and some isolated occurrences of elevated total suspended solids and total phosphorus. The results from these one-off samples resulted in Bay of Plenty Regional Council (BOPRC) prioritising incentive based funding through its focus catchment programme.

Ecology monitoring

Ecological information for the Waitepuia catchment consists of habitat and fish surveys. These are restricted to the lower parts of the catchment to date. Habitat assessments during the synoptic survey in November 2016 and 2017 indicated poor habitat quality (Carter, Davis & Suren, unpublished). Various fish surveys have been undertaken in the Waitepuia catchment between 1999 and 2016 (NIWA, 2020). Fish Index of Biotic Integrity (IBI), scores range from ‘poor’ to ‘excellent’.

The surveys also identify the presence of diadromous native fish species (shortfin eel, inanga, common bully, banded kōkopu, Galaxias sp., giant bully and redfin bully) as well as the introduced Gambusia sp. (NIWA, 2020). This indicates that these watercourses could be used as a migration pathway for diadromous fish to upper catchments, provided fish passage barriers (physical or chemical) were not an issue.

Regional Council staff have been gathering science and other information to assess the current state of waterways in the Waitepuia catchment and identify the causes of estuary degradation.

This work though ongoing has already clarified the issues and our land management team are now taking this information out to our communities and landowners and working with them to identify and implement on the ground action that can contribute to improving environmental health in the catchment and its estuary receiving environment Te Awa o Ngatoroirangi/ Maketū Estuary.

This work includes the provision of higher than normal grant funding along with free advice to landowners that encourage the uptake of best management practices such as drain re-contouring, stock-proof fencing, planting waterway margins and wetland restoration/construction.

Landowners can take action now. Regional Council offers practical advice and increased funding grants to help landowners within focus catchments to complete works that can contribute to improved water quality.

Funded works can include fencing, planting, nutrient budgeting, farm planning, detention bunds, treatment wetlands and many other activities. We can also help landowners to access funding from the Te Uru Rākau One Billion Trees Programme.

These incentives are for a limited time only.