Drainage management

waterways.jpgSouthland has an extensive land drainage system in place. This system consists of artificial drainage canals and community drains.  These drains periodically require maintenance work to be carried out to ensure that they perform the function they were designed for.

Some waterways flow constantly and others intermittently (ephemeral), but they are all part of a catchment and contribute to water quality.

Waterways on hill country farms are mostly unmodified natural waterways.  On more intensively farmed properties, the natural waterways have been highly modified to improve drainage.  In some cases artificial drains have been created to drain wetlands and to channel tile drain flows into waterways.

Waterways and artificial drainage not only transport water to the sea, but also carry sediment, bacteria and nutrients. While this is a natural process, intensive land use has significantly increased these amounts, which can impact both farm productivity and the life-supporting capacity of our waterways.

Ideally, all farmers should know which waterways on their farm are at risk of receiving excess sediment and nutrients, and how to minimise these amounts. Every waterway on a  farm needs to be considered, as even smaller waterways and ephemerals have the capacity to transport these materials.

Good management practices

  • Environment Southland encourages excluding stock from waterways by permanent or temporary fencing to maintain water quality.
  • Wherever possible, place your fences at least three metres away from the water’s edge. Wider buffers of up to 10 metres may be required on sloping land.
  • Crop preparation and stock grazing should be undertaken away from waterways – in some conditions a riparian buffer of more than three metres is required to protect water quality.

riparian-buffer.jpg
 

Current requirements

Some rules and consent requirements are around the management of waterways are summarised in the Farmers Rough Guide to the Rules .

  • Planting within 20 metres of a waterbody in large catchments (over 200 hectares in size) requires a resource consent.
  • Weed and sediment removal is generally permitted provided that certain criteria are met.
  • Deepening, straightening or piping a waterway is likely to require a resource consent from Environment Southland.

Definitions

Natural waterway
Any continually or intermittently flowing body of fresh water that is naturally occurring in the landscape.

Modified natural waterway
A water-carrying channel that existed in some form prior to land development but has been modified or straightened for drainage or other purposes.

Artificial waterway
A waterway that has been dug, piped, or was created to direct water along a channel that was not formed by natural events.

Ephemeral
A waterway that flows intermittently following rainfall or snowmelt.

Subsurface drainage
An artificial permeable subsurface conduit, constructed for the purposes of draining agricultural soil water/moisture with no direct or open connection, nor any connection via an artificial free draining area to the surface other than at the outfall. Examples include tile drains, mole drains, concrete drains, clay drains, wooden box drains and plastic subsurface drainage pipes.

Page reviewed: 05 Dec 2016 3:24pm