Meeting a Stock-Exclusion Consent on a Spring-Fed Stream
Ngati Rua Farms runs 280 Friesian-cross heifers on 160 ha near Te Awamutu. A 520 m spring-fed stream runs through three paddocks. The heifers cross it twice daily on the way to the shed, and the troughs in the far paddock are fed from it. Regional council monitoring shows E. coli of 2,400 cfu/100 mL downstream of the farm, and the resource consent requires stock exclusion from the stream by next June. Quotes are: full post-and-wire fencing on both banks plus a 4 m riparian planting strip, $31,000; a single hot-wire on the true left only, $8,500; a concrete culvert crossing plus fencing both banks, $24,000; piping water to six new troughs with a pump, $6,200. Farm profit before this work is about $60,000. Council may fund 40% of riparian planting costs. The stream has two small gravel beds used by banded kokopu. Staff say heifers will push through a single hot-wire when they are in season or spooked.
1. Recommend a package of works and a funding approach, and justify it against the consent condition, animal welfare and cost.
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Recommendation: culvert plus fencing both banks plus piped water - $24,000 + $6,200 = about $30,200, with the planting component in the fencing quote supported by the 40% council fund.
Reasoning
- The single hot-wire is the cheapest option and the wrong one. Staff have already told you heifers push through it when in season or spooked. A boundary that fails is not stock exclusion under the consent - it is a breach with enforcement risk, and it also fails on animal welfare, because a heifer that gets through a hot-wire and panics can injure herself or a mate. $8,500 spent on a fence that will need replacing is not a saving.
- The culvert is the key purchase. The stream is crossed twice daily. Fencing the banks while leaving the crossing unfenced would leave the highest-risk point untouched: heifers standing in the water, defecating directly into it, and pugging the bed and banks. A culvert removes that input and protects the gravel beds that banded kokopu use, which is directly relevant to both the consent and the ecological value of the stream.
- Piped water is essential. If the troughs draw from the stream inside the fenced area, the fence either gets broken for access or the animals go without water. Six new troughs on a pump removes the reason to go near the stream.
- Cost and funding: about $30,200 against $60,000 profit is heavy. Apply for the 40% riparian planting contribution, check whether the council has a stock-exclusion grant, and consider staging: culvert and water first (the water-quality gains), permanent fencing and planting in the second season to spread cash flow, provided the consent deadline can still be met. Confirm the deadline in writing.
2. Explain why fencing the banks on its own, without solving water supply and the crossing, is likely to fail both environmentally and practically.
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Environmentally
- The crossing is the main input point. An animal standing in the stream deposits dung and urine directly into the water and pugs the bed and banks, releasing sediment. Two crossings a day by 280 heifers is a large, concentrated load, and none of it is addressed by a fence on the bank upstream and downstream of the crossing.
- Sediment and phosphorus, not just E. coli. Bank collapse from stock pressure contributes sediment and attached phosphorus. Fencing that stops browsing and trampling helps, but not if the bank is already undercut at the crossing and continues to slump.
- Contaminated runoff still arrives. If the troughs draw from the stream and stock camp around a broken fence line or a leak, the contamination pathway remains.
- The consent test is stock exclusion, and an exclusion that is regularly breached does not meet it. Council monitoring will still show elevated E. coli below the farm, and the next sample will not distinguish between a good fence and a bad crossing.
Practically
- Animals need water. If the only supply is the stream and it is fenced off, heifers will find a way in - through a gate, under a wire, or by pushing a hot-wire. The fence then fails, and the investment with it.
- Handling risk. Heifers moving twice daily along a fenced lane with no crossing will bunch and pressure the fence, which is exactly where failures happen.
- Reputation and relationships. A visible, regularly broken fence is a poor look for the farm and undermines trust with the council and the catchment group, which affects future funding and consent applications.
The cheapest-looking option is the one most likely to be paid for twice.
3. Identify one significant long-term benefit and two real risks of the 4 m riparian planting strip, and state how each risk should be managed.
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Long-term benefit
A well-established 4 m strip stabilises the bank with root mass, filters sediment and phosphorus from overland flow before it reaches the water, shades the stream to keep summer water temperatures down, and adds woody debris and habitat that supports banded kokopu and invertebrate life. Over 10-20 years it becomes self-maintaining and reduces the maintenance the farm spends on culverts, crossings and drain clearing. It is also the part of the project most likely to attract council funding and community goodwill.
Risk 1: the strip fails to establish and is outcompeted. Young plants on a grazed, fertile bank face grass competition, rabbits, summer dry and, in this case, wet feet in a spring-fed system. Without care the planting is a row of sticks by Christmas. Management: plant at the right time for the district, use a species mix matched to the wetter bank and the drier shoulder, release-spray around plants for the first two seasons, use tree guards where rabbits are an issue, and replace losses in the first winter. Budget for maintenance, not just planting.
Risk 2: the strip takes grazing and interferes with farm infrastructure. Four metres each side of 520 m is roughly 0.4 ha out of production, plus the planting can block a drain outlet, obstruct a fence line or shading the paddock edge and reducing pasture growth. Management: plan the layout around drains, culverts and fence lines before planting, put the fence far enough back that the plants are not browsed through the wire, keep a mown access strip for maintenance, and site the troughs and lane so stock movement is unaffected. Agree the location and dimensions with the council before work starts so the strip meets the consent and the farm can still operate.