Water quality is a serious issue for New Zealand. Throughout our farmed land and urban areas, water quality has declined, some of it significantly, by contaminants nitrogen and phosphorus, microbes and sediment. In my last article I discussed winter pasture management and how good management will minimise the impacts on water quality. This time I will focus on waterway protection.
If you live on a property with a waterway, such as a river, stream, drain or wetland, a good first step in protecting water quality is to prevent stock from getting access – especially cattle, deer and horses who will readily enter water.
For most horse owners, the main reason to exclude their animals from waterways is to protect them from injury or even death. The cost of fencing can be weighed up against the risk of hefty vet bills, and the tragedy of losing a precious equine.
But as well as the risk to the animals themselves, the problem with horses (and other stock) having direct access to waterways is they increase sediment entering the water from bank erosion, as well as direct contamination from dung and urine, which nitrogen, phosphorus and pathogens.
With the nature of horses to tend to go where they shouldn’t, fencing is generally required rather than relying on a natural barrier. While for most of us, the ideal is expensive post-and-rail, on a basic budget you can use a portable electric that is only erected when horses and/or other stock are in the paddock. Portable electric fencing is also a good idea for areas that are prone to flooding. The key thing is that your fence prevents access to your river, stream or drain, and it is safe for your horses.
A question often asked is how far from a waterway should you fence. The easy answer is the further back from the edge of the waterway, the better. Firstly, the fence needs to be at least as far back from the bank of the waterway so as to prevent bank erosion and sediment entering the water. Secondly is the consideration of what the area between the fence and the waterway, known as the riparian margin.
Riparian margins are a key part of reducing contamination, as they act as buffers between grazed areas and the water. A healthy riparian margin helps filter pollutants and reduces stream bank erosion. Vegetation such as grasses will filter and prevent sediment entering water, whereas lager plants will also provide shade, which helps to lower water temperatures.
How wide the riparian margin needs to be will depend on a number of factors. On flat land, the riparian margin can be smaller (closer to the edge of the water) than on steep land. The rule of thumb recommendations are a minimum of 1m on flat land and 5m on steeper land. Before erecting a permanent fence, you should check with your regional council, as many have rules on fencing distances from waterways.
Managing your riparian area
A simple grass riparian buffer is an economic but effective option. If the area is large, you can graze it in the summer months with a light class of stock, such as sheep, which will not damage the banks and are unlikely to enter the water. A grass sward is also a preferable option for drains where access may be required so they can be cleared.
Another option is to plant with natives that can provide shade to streams and lower the water temperature, will encourage native species including fish. Native plants are preferable to exotic species, as the later can become weeds and infest the area. Faxes will encourage native bird life too, including tui. A well-planted riparian area can act as shelter protection from strong winds, and also adds amenity value to your property.
During the establishment phase, your riparian area will require weed control. If using a herbicide, ensure it is safe to use around waterways, as some can contaminate water. Your regional council or local native plant nursery will be able to provide advice on the best plants, planting time and specific management for your part of the country.
Identify your water bodies:
Identify areas that are flat and areas that are steeper. The steeper the land the wider your riparian margin should be to prevent contaminants entering water.
Consider your fencing requirements including:
- Type of fence
- Setback distance – check with your regional council for any rules on fencing waterways
- Plant selection – select plants suitable for your area and what you are trying to achieve
- Weed control and maintenance requirements
- This article was first published in the November 2019 issue of NZ Horse & Pony