Scalable Cost-Effective Solutions to Restore Stream Ecosystems

This paper aims to explore how with the right will and working together, diverse groups with an interest in our land drainage channels can collaborate to significantly enhance our waterways. Alternative approaches to land drainage management can create more environmentally sensitive and sustainable channel systems with the ‘whole of life’ aim of benefiting all parties, with support from local communities.

Historically waterways have been managed largely to ensure performance of their land drainage function, without consideration of the full range of values that they can offer. Healthy waterways where New Zealanders can swim, fish and gather kai is part of the national identity, but too often our waterways have been significantly modified and are severely degraded, with freshwater ecosystems impacted by poor water quality.

This paper will outline two areas in lowland Canterbury that, since late 2017, have been the subject of trials to test methods of waterway restoration. They are both spring-fed gravel bed waterways, with a range of native and introduced fish and invertebrate species, including native shortfin and longfin eel, inanga (one of the whitebait species) and introduced brown trout. The sites lie between Springston and the Waikirikiri/Selwyn River, which drains to Te Waihora/Lake Ellesmere, New Zealand’s fifth largest lake and an important wetland system with special significance as a tribal taonga (treasure) to Ngai Tahu.

Due to subsequent human activity, water quality has been impacted by excessive suspended sediment, nutrients and contaminants. High nutrients and a lack of shading allows aquatic weeds to flourish, blocking the flow and contributing to flooding, trapping sediment and causing fluctuations in dissolved oxygen. Land use intensification has also resulted in contamination of groundwater.

The trial site at Powells Road drain is being led by ‘Living Water’, a 10 year partnership between the Department of Conservation and Fonterra. On the Silverstream catchment, the work is led by ‘Fish and Game’ supported by the ‘Water & Wildlife Habitat Trust’ and others, with similar objectives.

This paper sets out the work completed to date (i.e. channel shaping, instream features and planting; to create habitat diversity and shading), both to maintain the land drainage function of the watercourse and enhance its ecological function, together with how the sites will be monitored, the early successes and lessons learnt. The importance of collaboration is emphasised, as is selling the vision to encourage and enable the wider community to embrace the change and give the Selwyn District Council a mandate for improved management. Initial setup costs are discussed within the context of the long-term potential benefits, as well as future plans.

A GIS database of watercourse suitability is under consideration, to help identify other trial areas across Canterbury and New Zealand. While these are likely to focus on rural farmland, there is little reason why many of the lessons learned cannot be applied within more urbanised areas, where opportunities present.

In summary, this paper will provide examples of sustainable whole of life waterway restoration solutions, demonstrating that tangible benefits of stream restoration can be delivered cost effectively.