Cooling off in a river or lake on a hot day is one of summer’s great pleasures. But is the water clear? Are the rocks slimy? Does it stink? Surveys repeatedly show that New Zealanders care about water quality – for swimming, drinking and food-gathering. For freshwater dwellers, it’s life or death.
Freshwater scientists rely on more than their eyes, skin and noses to assess water quality – they take objective measurements. A nationwide survey using measurements of nitrogen, phosphorous, suspended sediment and E coli levels was published late last year by the Our Land and Water National Science Challenge. It showed that even some catchments that include national parks and conservation estates need cuts in contaminants to meet bare-minimum water-quality standards. Some farming groups expressed concern that the standards must be too strict.
Ton Snelder, the report’s lead author, explains that the study shows only where improvements are needed at a catchment level. “Often, the headwaters start in places like DoC estates,” Snelder says. “It doesn’t mean everywhere in that catchment needs action – we haven’t identified where the dominant loads [of contaminants] are coming from.”
But natural areas do sometimes contaminate waterways, particularly with suspended sediment. “The Southern Alps shed a glacial flour of pulverised rock that clouds water, and the clarity is therefore technically below the bottom line,” says Snelder. It’s the same with phosphorous, which, in combination with nitrogen, drives slimy underwater algal growth that harms freshwater ecosystems. “Volcanic rock is high in phosphorous, which leads to naturally higher levels in certain regions, such as Taranaki.”
Snelder is clear that farmers are not expected to do things differently to compensate for naturally high contaminant levels. A clause in the 2020 National Policy Statement (NPS) on freshwater lets regional councils adjust regulations to allow for naturally high background levels. The Our Land and Water report is intended to help regional councils decide where improvements are needed in their catchments. Snelder adds that natural background levels aren’t a starting point for what is acceptable everywhere; freshwater ecosystems may cope with natural contaminants but there is a limit to the extra contaminants they can deal with from human land use.
The report’s biggest “fail” went to E coli, a bacterium that is used as a marker for faecal contamination. Three-quarters of our waterways have too much. The poo of birds and other wild animals contains it, but it’s not the main problem, says Snelder. “There’s a strong relationship between pastoral land use and E coli. There’s no doubt livestock poo is the big source.” Councils can tell which species it comes from, so livestock can’t be blamed for human or bird poo.
The government intends to replace the freshwater NPS, claiming it is too complex and expensive to implement. Snelder thinks the current one-size-fits-all approach to defining bottom lines could be tailored to regions, although that would sacrifice the simplicity of national standards. He believes our bottom-line water-quality standards are unambitious yet still not consistently met.
“A lot of the country would turn red in our maps if we looked at the load reductions required to achieve an A band or B band standard.”
The report compared real-life contaminant levels to only the C band of water-quality standards, or the minimum acceptable state, which Snelder says is consistent with international standards.
“It’s generally agreed that below this level things are not looking good. If communities want higher standards, they need to speak out – but consider what the economic cost would be, as it largely comes down to agriculture.”
