Thursday, 23 July 2015 05:47

Getting the banking in order

Written by 
Good riparian areas help keep waterways free of contaminants. Good riparian areas help keep waterways free of contaminants.

Winter weather can place extra strain on the banks of farm waterways, increasing the risk of erosion degrading water quality.

Since degraded water quality can affect animal health and productivity, protecting these riparian areas from erosion is important for environmental and economic reasons.

So it’s timely to look at the issues involved in erosion generally and less-than-ideal land management that can contribute to contamination of waterways.

Some of our rivers, lakes and streams have eroding banks, silted beds, water weed infestation and debatable water quality, often the result of poor land management.

Such practices, in farming, forestry, roading or horticulture, can cause soil erosion and a build-up of contaminants such as bacteria and chemicals which end up washed into watercourses during heavy rain.  

Some of the poor farming practises involved include stock wading in water, poor cowshed effluent treatment, overgrazing, inappropriate fertiliser application and pugging.

Poor runoff control on cultivated land, roads and tracks can also contribute to the contamination of water bodies.

Some of the impacts of poor practices can include potentially serious water-borne diseases like giardia and cryptosporidium. Nitrates and phosphates can also create health disorders for people and stock, and contribute to algal growth. Eroded sediment can hurt water clarity and aquatic life.

However, good management of riparian areas can reduce these types of effects by stabilising the banks and providing a filter for contaminants washing off the land. Effective management of the
banks is a key to protecting aquatic life and improving water quality generally.

A well-managed riparian margin, with a carefully selected mix of species, will filter out contaminants such as sediment and nutrients from farm run-off, including soil, animal dung and urine, and agricultural chemicals.

Shrubs and trees with extensive root systems, which tolerate moist soil conditions and frequent silt deposits, are ideal for stream bank erosion control. They physically hold the stream banks together and some tree roots also protect the streambed, limiting the scouring effect of running water.

Streamside vegetation provides shade which reduces water temperature, improves dissolved oxygen levels, helps aquatic life and reduces the risk of algal blooms.

Suitable plant species beside waterways also provide cover for spawning fish, and food and habitat for nesting and young birds.  Such planting helps water plants and invertebrates become numerous, providing a better food supply for fish. Streamside trees can link areas of native vegetation, extending habitat for native birds.

Besides environmental benefits and generally protecting water quality for stock, riparian planting can also help a farm’s economy in various ways.

Well designed riparian fencing can be used to improve subdivision, help with mustering, and protect animals from drowning or getting stuck in wet areas.  The provision of shelter and shade is recognised as an important aspect of animal production and health.

Improved milk grades are documented where dairy sheds no longer draw water from contaminated streams.  On sheep and beef properties, stock enjoy better health and gain weight faster when water sources are not contaminated.

• Bala Tikkisetty is a sustainable agriculture advisor at Waikato Regional Council. Tel. 0800 800401 or email This email address is being protected from spambots. You need JavaScript enabled to view it.

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