Freshwater management

Water in New Zealand remains a public resource. Freshwater and rivers are a "public good" owned by everyone and managed by the Council on behalf of the public. For example, an individual may have a water permit to take a certain amount of water from a river for domestic use or irrigation, but the water itself cannot be owned by an individual.

How freshwater is managed

Public resources such as water and air are managed differently from privately owned resources such as land. Land use activities are generally allowed unless a rule requires otherwise. In contrast, activities involving water or water bodies can only occur if they are expressly allowed by a rule in a regional plan, or by a resource consent.

Nelson's freshwater resources include:

• Urban streams (streams which mainly flow through an urban environment and have high levels of modification - Oldham Creek, Brook Stream, York Stream, Jenkins Creek, Arapiki Stream, Poormans Valley Stream, Orchard Creek, Orphanage Creek, lower Maitai River and Brook Stream).
• Rural rivers and streams including those in exotic forestry catchments (includes the Whangamoa, Wakapuaka, upper Maitai and many smaller named and un-named streams).
• Unmodified streams and tributaries (such as Maitai South Branch and many un-named streams in catchment headwaters).
• Artificial lakes and reservoirs (Maitai Dam reservoir and rural reservoirs).
• Springs.
• Wetlands (limited to Rush Pool, Dew Lakes , the Wakapuaka River and Whangamoa River flats at the river mouths, and the Wakapuaka Sand Flats at the head of the Haven).
• Groundwater (unconfined, which is likely to be hydraulically linked to surface water, and confined).

Freshwater Provisions

The Freshwater provisions in the Nelson Resource Management Plan address five main areas.

Activities and structures in and near waterbodies

The Resource Management Act (section 13) places special restrictions on the use of river beds. Any structures on, or disturbance in, river beds must be provided for by a rule in a regional plan or by a resource consent.

However, the purpose of the Resource Management Act (section 5) includes sustaining physical resources, which includes bridges and buildings which can be threatened by flooding and other natural processes of water bodies. For this reason some flood protection and maintenance of structures in riverbeds is necessary to achieve sustainable management.

The use of river beds is less widespread than the use of water which flows over them, but such uses still have the potential to result in adverse effects on the environment. Activities or uses of river beds include bridges, fords, dams, weirs, water intake structures, river control works, and vegetation planting and clearance. Adverse effects include erosion and build up of sediment, poor water quality, damage to aquatic habitats and obstacles to fish passage.

Activities such as channelisation, channel realignment and rock works can have significant and permanent effects. Other activities, such as vehicles in river beds, may have temporary adverse effects, which if regular could have a cumulative effect.

River control works exist on the Maitai River and on most urban streams. There are bridges and fords on most of Nelson's rivers and streams. However, there are still unmodified reaches of most rivers and streams. It is important to manage activities and structures in these water bodies to retain the ecological integrity, hydrological functions, and sediment transportation functions of the river systems.

Natural character, amenity and public access

Natural character is what is generally created by nature and not by people, so it is reasonably easy to objectively assess how much natural character a place has. Every river and stream, to some extent, has natural character.

Amenity values are more subjective. They are the aspects of a river and its surroundings that make it a pleasant place to visit and enjoy, to experience nature, or to participate in recreational activities.

Public access - The RMA requires the Council to give high priority to public access but it is also important to respect private property rights, and ecological functions (for instance public access may disturb bird breeding).

Aquatic biodiversity

Water bodies and their margins provide a range of different habitats for a diverse range of flora and fauna.

• The riparian margins are home to land dwelling animals as well as amphibians such as frogs.
• The water in rivers and streams is a habitat for plants and animals, including some birds.
• A different range of animals and plants inhabit the bed of rivers and streams.
• Life forms also exist in underground water resources.
• Wetlands provide a habitat which is part aquatic and part land-based, attracting a unique range of plants and animals.

Fish species

The following fish, crayfish and shrimp species have been recorded in the Nelson area:

• Shortfin eel (Anguilla australis)
• Longfin eel (Anguilla dieffenbachia)
• Torrentfish (Cheimarrichthys fosteri)
• Koaro (Galaxias brevipinnis)
• Banded kokopu (Galaxius fasciatus)
• Inanga (Galaxias maculatus)
• Upland bully (Gobiomorphus breviceps)
• Common Bully (Gobiomorphus cotidianus)
• Giant bully (Gobiomorphus gobioides)
• Redfin bully (Gobiomorphus huttoni)
• Common smelt (Retropinna retropinna)
• Brown trout (Salmo trutta)
• Yellow eyed mullet (Aldrichetta forsteri)
• Koura (Paranephrops planifrons)
• Freshwater shrimp (Paratya curvirostris)

Threats to aquatic life include: discharges directly into water, water abstraction, bed disturbance, and physical changes to the bed resulting from gravel extraction, erosion protection and flood protection.

Water quality

When water quality is poor the communities of aquatic animals become impoverished, with only the most tolerant kinds of animals (such as worms and snails) able to inhabit these streams.

The types and numbers of invertebrates in a water body are important to a freshwater ecosystem. Where densities of drifting invertebrates such as mayflies and caddis flies are low, there is less food for native fish and trout.

Fish passage

Freshwater fish have varying abilities for making their way inland from the sea. Some fish only inhabit streams and wetlands within our coastal lowlands. Other fish are able to swim long distances inland.

Without free passage up and down our streams, many species would not be able to find the right habitat and conditions to breed. Whitebait, for example, migrate varying distances inland from the sea to grow and mature in their preferred adult habitat, often in very small streams.

Water flows and allocation

Water flows

Water is a limited resource in Nelson City . Our low rainfall dictates the quantity of water in rivers. Low flows can result in unacceptable stress for fish and aquatic invertebrates.

The Maitai and Roding Rivers are used for public water supply, while water from some of the smaller streams is used for irrigation and private water supplies. Most rivers are also used directly or indirectly for stock drinking water.

Keeping enough water in Nelson's rivers and streams to maintain their healthy state is the reason for setting limits on how much water can be taken out of them for other uses.

Resource consents cover most of these abstractions although some, such as reasonable domestic and stock water takes, are permitted without Council consent being required.

Groundwater levels and flows

The extent of Nelson's groundwater resources is not known. However, useable groundwater is thought to be limited, with a number of springs and private wells/bores on rural properties.

Water quality

Nelson's water quality

High quality water occurs in Nelson's conservation estate and more remote rural land including the upper reaches of the Maitai, Wakapuaka and Whangamoa rivers.

Slightly disturbed but largely healthy water bodies occur where the Conservation Zone changes to the Rural Zone but land use is not intense, such as the upper to mid reaches of the Maitai, Wakapuaka and Whangamoa rivers.

Moderately disturbed water bodies typically occur in the Rural Zone and currently include the mid to lower reaches of the Maitai River , Wakapuaka River and Whangamoa River as well as many of the tributaries of these rivers. The urban mid reach of Brook Stream and lower reach of the Maitai River also have this level of water quality.

Almost all of Nelson's urban streams are physically, chemically and biologically degraded or very degraded, including all of the water bodies in the Stoke area, the Atawhai and Glen streams and the lower reaches of Brook Stream. This means they no longer provide good habitat for the animals and plants reliant on them.

Effects on water quality

Water quality in rivers and streams is strongly linked to activities in their surrounding catchments. Contaminants such as nutrients, heavy metals, fine sediments and faecal bacteria enter water bodies via direct point source discharges (such as urban stormwater and industrial discharge pipes) and indirect non-point source discharges (such as runoff from agricultural or cleared land).

These contaminants can have a variety of adverse effects on water quality. For example, high nutrient levels (nitrates and phosphates) can lead to increased growth of algal slimes. As well as being visually unappealing, prolific growth takes oxygen out of the water, further degrading the living conditions of invertebrates and fish communities

Effects on fish and insects

Fish activity and spawning, and survival of "pollution-sensitive" aquatic invertebrates (such as mayfly larvae) can be affected by changes in water chemistry and habitat. When the invertebrates which are most sensitive to poor water quality diminish, so too do the native fish and trout that like to eat them, so the type of fish in the river changes. They are replaced with bottom feeding fish such as Rudd which stir up the sediments, leading to less clarity in the water and diminished aesthetic values.

Effects on humans and domestic animals

In addition, higher contaminant levels in water can directly harm the health of humans, domestic animals and/or aquatic life. Heavy metals can be toxic to aquatic animals, killing them or affecting their breeding. Water contaminated with faecal bacteria can make people (and stock) sick and can pass on infectious diseases, making water unsuitable for swimming or drinking. Unless we work to avoid, remedy or mitigate the entry of contaminants into our water bodies, they will compromise many of the things we value about our fresh waters.

Sources and effects of common contaminants

Nutrients (such as nitrates and phosphates)

Where they come from

• Runoff from agricultural & cleared land
• Runoff from urban land

Effect on water bodies

• Increased growth of algae (slime) and/or aquatic plants
• Decreased amounts of oxygen in the water, or big daily fluctuations in oxygen (due to algae growth)

Heavy metals

Where they come from

• Urban stormwater runoff (from residential & industrial properties & roads)
• Many are bound to fine sediments

Effect on water bodies

• Can be toxic to aquatic animals, killing them or affecting breeding
• Can bio-accumulate (increase in quantity in animals)
• End up in estuaries or the sea where they can be toxic to marine life

Pesticides

Where they come from

• Agricultural and garden runoff

Effect on water bodies

• Can be toxic to aquatic animals

Fine sediments

Where they come from

• Runoff from cleared land
• Urban stormwater runoff (e.g. roads, gardens, construction sites)
• Unvegetated/crumbling stream banks (commonly caused by stock trampling)

Effect on water bodies

• Decrease water clarity
• Decrease habitat for aquatic animals, by filling in the gaps between stones in the streambed
• Interfere with fish spawning
• Increase loads of nutrients and other pollutants, which are bound to sediments

Faecal bacteria

Where they come from

• Runoff from agricultural land
• Stock crossings or stock grazing riverbanks / drinking from streams
• Seepage from septic tanks

Effect on water bodies

• Make water unsuitable for swimming and other contact recreation
• Pass on infectious diseases

Best management practice

Planting streamside vegetation

This stabilises stream banks and provides shade which keeps water cooler and provides cover for animals living in the river. Cool water is more oxygen-rich than warm water.

Best management practices for control of discharges in New Zealand include the following:

• controlling the generation of sediment and contaminants before they enter the stormwater system in the first instance;

• controlling livestock access to watercourses;

• using grassed riparian margins and filter systems to control the flux of sediment and contaminants into water bodies;

• using interceptor filters in kerbside sumps, sediment traps, mini-wetlands and detention ponds to control and treat sediment and contaminants entering the stormwater system;

• better design and operation of septic tanks; and

• permeable surfaces for public hard standing areas such as car parks. which allow natural soil filtering.