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  • Learn how farms can keep waterways healthy for those downstream and for our precious native freshwater fish, all while benefiting farm health and the farming operation’s bottom line.

    A farm without a stream is like a fish with a bicycle – pretty rare! The network of streams and even drains that cross farmland may be less than pristine, but chances are they still harbour a community of native fish, invertebrates and aquatic plants. Coastal farm streams may be a nursery for the local whitebait run, while high country sheep farms could harbour a rare mudfish or two.

    Recent statistics show that 72% of 39 native freshwater fish species (that are reported on) are either threatened with or at risk of extinction. About a third of native freshwater plants and invertebrates are also at risk.

    Keeping streams well shaded and free from stock trampling, effluent and silt while ensuring culverts are fish friendly will give native freshwater fish the best chance of surviving on the farm. Like the miner’s canary, the types of fish and invertebrates that live on a farm are a great indicator of healthy water and good farm stewardship.

    Learn how farms can keep waterways healthy for those downstream and our precious native freshwater fish, while also benefiting the farming operation.

    Useful link

    Read the latest statistics on the state of freshwater from the Ministry for the Environment and Statistics New Zealand in their report Our Fresh Water 2017.


    This resource has been adapted from the Hooked on native fish downloads developed by the NZ Landcare Trust. The Science Learning Hub acknowledges the help of the NZ Landcare Trust in adapting this work.


    Plant steep areas

    Don’t watch the farm go down the drain! Planting up steep slopes, gullies and stream banks will reduce soil erosion off the farm and keep silt out of the water. Many native freshwater fish cannot tolerate water that has been muddied by excess sedimentation.

    Steep areas on farms are often unproductive. There is ongoing work being done to investigate how to control erosion on these marginal sites while also increasing productivity, such as Mānuka plantation research for medical-grade honey.

    Acknowledgement: Showdown Productions

    Prevent algal blooms

    Healthy water means healthy stock. This means preventing excess nutrients from leaching or running off into waterways. Excess nutrients from fertilisers and effluent coupled with hot weather and unshaded streams fuels eutrophication and algal blooms that can be fatal to humans, dogs and livestock. Prevent algae growth by fencing and planting waterways to cool the water. Where fencing is impractical, install drinking troughs and shade at the top of the paddock to encourage stock away from swamps and streams.

    Dr Ross Monaghan

    Nutrient leaching is an environmental issue for two reasons. The first is too much nitrate getting into our groundwater aquifers that are used for drinking water supplies. High concentrations of nitrate in drinking water that’s used for making infant formula poses a risk to young infants because they can’t process that nitrate that we as adults can. So we want to make sure that the drinking water we provide has a concentration that the World Health Organisation recommends is less than about 10 milligrams of N per litre.

    The second aspect that is coming to attention more frequently in New Zealand and abroad is the problem of eutrophication. Eutrophication is a term that describes the nuisance growth of weed and algae in surface waters, in streams and estuaries. That process is really driven by two nutrients – nitrogen and phosphorous. So nitrate that leaves this farm ends up in a lake or an estuary. If it arrives with phosphorous, together, that’s quite a fertile combination that will promote that nuisance weed and algal growth. And the growth can have lots of undesirable effects in terms of how we might be able to use that water for recreational purposes, and habitat value, choking out all the other wildlife that can occur.

    Winter is a high-risk period for nitrogen leaching because of at least two reasons. The main one is that it’s the time of year when we have a lot of surplus rainfall arriving and thus a lot of drainage and transport of any nitrogen that’s sitting in the soil, potentially available for leaching, and secondly, it’s a time of year when plant uptake is quite low, so particularly if you’ve got a relatively bare paddock, for example, a forage crop paddock that’s been recently grazed, there’s a lot of nitrogen that’s being returned to that paddock in the form of urine but very little plant uptake until temperatures warm up in the following spring. So those two factors cause winter to be a high-risk leaching loss period of the year.

    Acknowledgements: © University of Waikato with additional materials courtesy of Dr Ross Monaghan/AgResearch; Juliet Milne/Otago Regional Council; and Tamara Douglas.

    Plant wet areas

    Boggy seepages, peat bogs and springs on the farm are an important source of water for streams, especially during dry summer months. These wetland areas are also important for filtering out excess nutrients before they can reach other waterways. Instead of draining, fence and plant with native sedges, toetoe and harakeke so they form a buffer zone to absorb and slow down run-off after heavy rain.

    Acknowledgement: University of Waikato

    Care for drains

    Don’t drain away the farm profits. Fencing and planting drains helps to shade out weeds and keeps silt out, reducing the number of times they need digging out. Less maintenance saves time and money.

    Acknowledgement: Ross Henry, 123RF Ltd

    Reduce nitrogen

    Go easy on the nitrogen. Nitrogen sources on the farm are animal effluent deposits or fertiliser application. When nitrogen levels on the farm exceed what the pasture and plants can take up, the excess often ends up in waterways. Further, it can be converted to nitrous oxide (N2O) – a greenhouse gas that contributes to the greenhouse effect, which is a driver in climate change.

    Managing nitrogen on the farm is good farm practice. Farmers can do this in a variety of ways, from planting nitrogen-fixing crops to employing nutrient budgeting tools. Retiring eroding steep hills and boggy areas will also help reduce the amount of nitrogen running off or leaching into waterways. Read more about nutrient management on the farm, or use our interactive to learn more about the Terrestrial nitrogen cycle.

    The recent government report Our Fresh Water 2017 confirms that nitrates and nitrogen levels are increasing in our waterways.

    Dr Ross Monaghan

    Some of the farm management practices that are most commonly employed to minimise the risk of nitrogen loss are to make sure that you don’t apply too much nitrogen per application or too much in any one year. We make sure that farm dairy effluent we’re collecting back in the milking parlour is well managed, so it’s returned to land at a low rate. Something that can help reduce direct losses of urine near to streams is just to prevent stock from urinating directly into those riparian zones.

    Another strategy involves being careful about when urine is deposited back to pastures. Where we can have animals under cover or on a stand-off where we capture the urine and we store it through the risky winter period and return it to land in the following spring, we can reduce nitrate leaching losses quite considerably.

    One important strategy for helping to manage the nitrogen problem is the way we look after riparian and wetland areas. Wetlands are really important parts of our landscape that act as filters for some of the run-off, particularly for filtering out nitrogen that’s passing through wetlands. So it’s really important that we protect the wetlands that we have remaining and reinstall some that have been drained and are perhaps overgrazed and to make sure that we don’t allow stock to graze those riparian zones and either cause treading damage or excrete urine or dung directly into the waterways.

    Urine is very high in nitrogen, and in the case of dung, it’s quite enriched with phosphorous and faecal bacteria. Phosphorous contributes to that eutrophication issue, and faecal material can carry with it zoonotic microorganisms that can make us sick, so we want to avoid that risk altogether as best we can. The main way is just to put up a fence.

    The Overseer® tool is a nutrient budgeting model that has been developed with input from other universities and CRIs. It’s a tool to help just guide nutrient management, and particularly inputs of fertiliser, but also to make sure that we don’t double up on fertility from effluents as well as from fertiliser. And increasingly, that tool is being used as a calculator to determine, for example, the nitrogen footprints to either water or to atmosphere from different types of farming activity and different types of landscapes and soils and climates. That tool is going to be essential to allow us to explore ways by which farmers can look at their budget and say, “OK, how can I maximise my nutrient efficiency, how can I minimise my losses, and how can I get the most bang for my buck in terms of purchasing fertiliser?”

    Acknowledgements: © University of Waikato, with additional materials courtesy of Dr Ross Monaghan/AgResearch and McDonald’s Lime.

    Fence stock out

    Stock can damage stream edges, and the direct depositing of their faeces (poo) and urine into the water dirties the water and adds to the rising nitrogen levels. Native fish need good stream banks for hiding in and laying eggs, and they’re also intolerant of dirty water.

    For farmers, hauling cows out of swamps and waterways on a miserable winter night is no fun. A good dairy cow can be valued at $1,500, so losing them is expensive.

    Farmers all around the country are realising good environmental practices, such as fencing off waterways, makes good business sense and is good farm practice too.

    Acknowledgement: University of Waikato

    Fish-friendly culverts

    Fish passage is critical for our native species. Many need to be able to migrate in order to complete their life cycle.

    Look at the culverts on the farm and identify culvert crossings that work well for fish and those that don’t. Fix those that aren’t working by adding ramps and/or baffles.

    When looking to install new culverts, make sure these are fish friendly too!

    Cheri van Schravendijk-Goodman

    The problem with culverts in tributaries are that they disconnect habitat from the main stem of the river. A culvert is a big pipe, often used for helping with drainage of land, but the problem with the culverts is they tend to sit kind of this high off the surface of the water or maybe a bit closer depending on what the river’s doing. Now our whitebait – species like kōkopu and that – they can climb but they can’t jump. They’re not superfish.

    Fish ramps and baffles are infrastructure that we’re going to hopefully retrofit to these culverts and floodgates to improve connectivity between the river and the tributary, because kōkopu and kōaro like to get up into those tributaries, probably īnanga as well, and they perhaps could be where they’re spawning, so we want to make the passage as smooth as possible without impacting on the actual adjacent land use, you know, because the culverts and that do perform a function. Often it could be related to human safety, particularly the floodgates. We don’t want to make it difficult for humans and nature to co-exist.

    Rock ramps or a fish ramp is a way for reconnecting those tributaries that have these barriers like these culverts and floodgates.

    The techniques that have been applied by NIWA is using rocks embedded into concrete ramps. Our fish are really good climbers, our galaxiids, and so you try and create a way to help them get up to that culvert. It also provides a rest spot for the fish.

    A baffle is a rocky substrate or a brick or something inside the culvert, and again that’s about giving the fish something to climb up on to and to rest.

    Culverts create a really unnatural system. Normally, when these tributaries come down, their flow would be slowed down by twists and turns and rocks and stuff. Culverts are just one straight smooth system, so the water velocity can get really, really fast and hard. By putting baffles in there, you’re not only giving an opportunity for these fish to be able to climb up the incline of those culverts but also giving them a bit of a place to rest and be protected sometimes when they’re tired.

    Acknowledgements: © University of Waikato with third-party materials courtesy of Cheri van Schravendijk-Goodman, Dr Bruno David (WRC) and Dr Cindy Baker/NIWA. Certain photos in this video are the copyrighted property of 123RF Limited, their contributors or licensed partners and are being used with permission under licence. These images and/or photos may not be copied or downloaded without permission from 123RF Limited. The Waikato Tainui College for Research and Development acknowledges the financial support given by the Waikato River Cleanup Trust Fund, which is administered by the Waikato River Authority. The Waikato River Cleanup Trust does not necessarily endorse or support the content of the publication in any way.

    Rights: University of Waikato Published 18 December 2017, Updated 4 April 2018 Size: 870 KB Referencing Hub media
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