Whangaehu Freshwater Management Unit 2023

Horizons Regional Council is working collaboratively with Post-Settlement Governance Entities in the region for Treaty river settlements. This is to ensure our work supports the objectives of the strategies being developed under Te Waiū o te Ika for the Whangaehu River. Our approach to implementing the National Policy Statement for Freshwater Management (NPS-FM) in the Whangaehu Freshwater Management Unit (FMU) needs to support the river settlement legislative processes and the outcomes sought in the resulting strategies. The information presented here summarises the scientific information held by Horizons about the Whangaehu FMU.

The Whangaehu Freshwater Management Unit, or FMU, encompasses the area in and around the Whangaehu River and its tributaries, the Mangawhero and Makotuku Rivers.  The area also includes several lakes and wetlands.

Emerging from the crater lake and slopes of Mount Ruapehu, the Whangaehu River begins its journey down the eastern side of the mountain. From here it flows east, across the central plateau and Rangipō Desert. The river is contained in a lahar channel, created by the volcano, with high steep sides that often fall into the water. The river continues its journey through native forest before releasing into the Tasman Sea on the west coast.

The stories of the river and the humans who live alongside it are intertwined.

The Whangaehu FMU is a mixture of landscapes that includes significant pastoral farming, forestry, hill country and urban centres. The FMU is also home to extensive forest cover, including ice and snow cover, alpine tussock land, scrub and indigenous forest. A significant area of the Tongariro National Park sits within this FMU.

The activities that people undertake in the region have, and continue to have, an impact on freshwater in the Whangaehu FMU. 

The pressures on freshwater in the Whangaehu FMU today include:

• Discharges, including wastewater and stormwater, can carry bacteria and excess nutrients into rivers, lakes and streams.   
• Abstraction of freshwater from rivers, lakes and streams for human use reduces water available for aquatic life.  
• Alteration of physical aspects of the ecosystem, such as damage to river channels, can impede access to habitats for freshwater species.  
• Invasive freshwater weeds can threaten native species and degrade the quality of the water. 
• The risks associated with the impact of climate change.  
• Land used for activities such as agriculture or urban development, contributes bacteria, nutrients and sediment (sand, soil and silt particles that have detached from the land by erosion) that enter the freshwater systems.

We all have a responsibility to manage our activities in a way that sustains the life-giving capacity of freshwater, safeguarding it for future generations.

Iwi/hapū, local and central government, farming and industry leaders, and environmental and recreational advocacy groups have, and continue to address some of the challenges facing the Whangaehu FMU.

These groups have fenced and planted along the waterways (riparian planting). The fences keep wandering stock out of the water. The plants help filter nutrients, sediment and bacteria that leave the land as runoff.

Land used for grazing animals has been retired and planted with native vegetation. These actions create protective environments for wetlands, rivers and streams.

Land that is prone to hill country erosion is being managed through land retirement, spaced pole tree planting, the regeneration of native bush and the establishment of forestry. These actions have reduced sediment entering rivers and streams.

Barriers to fish passage are being remediated or removed, in some instances improving the connectivity of habitat for aquatic life. 

Upgrades to wastewater treatment plants have reduced the impact of contaminants on rivers and streams. This is an area of continued focus for this FMU.  

Actions like these reduce the impact of human activities on freshwater environments. Over time, these initiatives will gradually improve the health of Whangaehu’s waterways.

Every water body (rivers, lakes, streams, wetlands and aquifers) has a unique ecosystem consisting of all living things and the physical habitat that they interact with. 

Ecosystem health is the ability of water bodies to support all life, including fish, birds, insects, plants and microbes. Pressures from human activities can impact ecosystem health. 

We, the people that live, work and play around the river, form part of the Whangaehu ecosystem and have a duty to care for it.

The Whangaehu FMU has some fantastic places to enjoy the water on a hot day. Locals use the waterways to cool off, swim, fish, kayak or walk alongside.

But how do we know when the quality of the water is good enough for our whānau to enjoy? 

If you go for a swim or fall out of your kayak in the river, you are making direct contact with the water. 

At times, rivers and lakes may contain elevated levels of  faecal bacteria  and potentially toxic algae, making them unsafe for direct contact. Encountering high levels of these bacteria can cause stomach upsets, vomiting and other signs of gastrointestinal illness. 

Horizons collect two sets of data: 

1. Weekly monitoring at popular swim spots over the bathing season (November – April) to help you decide where to cool off on a summer day.
2. Monthly monitoring where staff check representative sites across the FMU year-round. 

The indicators that determine the grading for direct contact are E. coli for freshwater sites and Enterococci at coastal sites. These indicators of faecal contamination can increase significantly with high rainfall causing contaminants from urban and rural settings to wash into waterways. In the future,    cyanobacteria    will also be included in our reporting.

Freshwater is precious; it makes up only 3% of all the water on earth.

During summer or in periods of drought, demand for water increases and river levels are at their lowest. Rivers and streams cannot afford to have too much water removed as low levels threaten ecosystem health. 

People use freshwater for human and stock drinking water, irrigation for agricultural land or horticulture, hydroelectric power generation, and processes in other industries. 

Freshwater plays a significant role in supporting communities across the Whangaehu FMU.

The Whangaehu FMU is divided into 11 surface water management sub-zones. Each zone has a water allocation limit to manage resource use. Some of the allocation limits are reduced to account for water diversions for hydropower generation. The amount of water allocated to users against these limits varies across the FMU.

A considerable amount of the country's freshwater is stored as groundwater in aquifers. 

Aquifers are large areas of layered gravel, sand and rock that act as a sponge, removing and holding water away from the surface. Water stored in aquifers is replenished by rainfall.  

Aquifers can be connected to surface water, sometimes supplying lakes, rivers and wetlands with freshwater from below. Other times groundwater is replenished through interaction with these water bodies.  

There is one groundwater management zone in the Whangaehu FMU. Much like surface water, limits have been set to protect the groundwater resource. The groundwater management zone in the Whangaehu FMU is managed well within these limits.

We can not report on the status of groundwater quality in the Whangaehu FMU as we do not have monitoring sites within this rohe. Horizons will investigate more groundwater work in this area as part of our science work programme in the future.

Explore more about groundwater on the  LAWA website .

If you have any further questions about freshwater you can call us on freephone 0508 800 800 or email us at  info@ourfreshwaterfuture.nz .