Clean Water | Nitrates, Oxygen, Turbidity, Conductivity, Temperature

Recent clean water legislation is putting new obligations onto farmers, and local and regional authorities to monitor and report water quality. Read how new IoT tools and connectivity networks have arrived just in time to assist in the challenge of cleaning up New Zealand’s waterways and aquafers.

clean water nitrate level reduction

The Clean Water Challenge

There are few things as many people agree on as the need for clean water.

Growing awareness by the public of the potential impact on our waterways from intensive farming and industrial pollution, seen the creation of new freshwater legislation across the entire country for farmers, community groups, businesses, local and regional councils.

While these are proving unpopular with some rural communities, there are two facts that are becoming clearer by the day: pollution of our waterways has significant potential health implications for all New Zealanders; and legislation is coming to ensure everyone plays their part in fixing New Zealand’s waterways.

Clean Water?

Much of the new legislation around clean water is focussed on nitrates in the water supply. This is a more easily measurable indicator of water conditions and is a direct outcome of intensive farming practices and pollution. Chances are that most bore-water drinkers (estimated at 75% of the population) have had some level of nitrates in their drinking water without them knowing or noticing.

Nitrates end up in the water supply from intensive farming through a number of different channels. Nitrogen is pulled out of the air by clover for example where it is eaten by cows – if more nitrogen is eaten than is needed by the cows, it gets excreted onto farmland, where (if it is not reabsorbed by plants) leaches down through the soil into the waterways.

That process gets amplified if the farmer adds synthetic fertiliser or spreads too much excrement onto the paddocks to speed grass and clover growth. As a result, the volume of nitrates needed to be reabsorbed naturally may become too extreme for natural processes and much of it goes down through the soil to aquafers, or runs off the fields into nearby streams or rivers.

In recent decades, nitrate levels in our waterways has been growing and in some places it is exceeding this maximum level. A Danish study recently showed that the impact on the health caused by nitrates is an increase in colorectal cancers, undersized infants and what’s referred to as ‘blue baby’ syndrome. The bad news is that these health issues can begin to occur at less than half of our ‘Maximum Acceptable Value’ for drinking water of 11.3 mg/l nitrate-nitrogen.

farmers monitor nitrate runoff

Other Pollution Issues

Human health aside, the impact of pollution in our environment caused by nitrates is well known. Phosphates and nitrates typically promote excessive growth of algae. As algae dies and decomposes, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish.

This ‘eutrophication’ of a waterway usually gets worse in an estuary for example, where excessive nutrients cause algal blooms and smelly, putrid water. This is the reason aquaculture farms stop harvesting after large rain events, as the potential for runoff causing [shellfish poisoning] increases dramatically as nutrients are washed off the land, into rivers and into the sea.

Another issue is an increase in ‘turbidity’, with runoff of silt, plant matter or pollutants causing water to become cloudy or opaque. An increase in turbidity can indicate other water-health issues such as silting up of estuaries resulting in shellfish dying off and fish spawning areas being impacted.

farmers need to monitor nitrate leaching

Legislation Changes

As we said earlier, the Government has taken action to attempt to limit nitrate and nutrient runoff from farms with wide-ranging legislation. From this year, areas used for intensive winter grazing must comply with the Certified Freshwater Farm Plan.

In 2020 new Wetland management rules were imposed and new Winter grazing restrictions imposed, and this year a Nitrogen fertiliser cap was added, along with stock holding restrictions.

And in 2023 further rules come into force, with mandatory water use reporting. Irrigation consent holders who take more than 5-20 litres of water per second will need to measure water use every 15 minutes and electronically submit records to the council every day. And Dairy Farms will be required to report nitrogen use by 31 July each year.

monitoring nitrates level in NZ rivers

IoT Tools and Solutions

Mandatory reporting could potentially add significant administration demands onto intensive farmers in particular and there is some concern in the sector about the cost and logistics of compliance.

But the story isn’t all bad – the IoT has arrived on the farm with new tools, just in time to automate some of the more onerous and data-driven jobs.

Adroit is already installing real-time water monitoring stations using sondes (multiple parameter sensors) onto land-based farms, aquaculture farms and waterways to provide minute by minute reporting of a number of important metrics:

  • Nitrate content of water in wells, bores and streams
  • Dissolved Oxygen (an indicator of water health)
  • Turbidity (sediment particles in the water)
  • Conductivity (measures salinity)
  • Temperature

Adroit has several installations utilising In-Situ sondes. In-Situ sondes can fit up to four sensors performing different measurements inside each sonde, as well as an automatic wiper, which cleans the sensor cage. They even have a copper guard to allow installation into saltwater environments to stop any fouling.

Nitrates are measured by a s::can optical nitrate sensor that uses a UV laser light through the water to provide a nitrate level and a total suspended solid level as well. If more parameters need measurement, we can look at other parameters of UV nitrates including biological metrics.

Nitrates and nitrites are seen in the same water spectrum range. So we only get a N03-N reading, which then gets converted into NO3. We can delve deeper and we can go into the effects of nitrites, with more specialised sensors.

testing equipment for nitrates in rivers

A typical installation would be to install a sensor or sonde at the upstream and downstream boundaries of a stream that travels through a farm and to monitor for changes. When combined with bore or well-based sensors, the farmer can get a good idea of what actions taken on the farm mean for the water around and below the farm.

Additional reporting from a weather station can then provide the farmer with data on how rainfall effects nitrate leaching, for example, especially when combined with data on fertiliser application volumes and timing. And other machinery can be connected into the IoT ecosystem to provide a full picture of the farm.

Until recently, connectivity was an issue for IoT on the farm or other remote locations. Now, specialised IoT networks such as Spark’s Cat M1 allow real time reporting from any location, with solar panels providing power to the equipment.

These types of tools can give those responsible for the waterway the data they need to fulfil Government regulation, but also can give them an insight into the impact of their land on the environment and, over time, gradual changes can be made to their processes to not only halt waterway degradation, but to improve the overall health of the streams and aquafers around and under their property.

In Summary

Clean Water is often seen as a battle between farmers/industry and Government – whether local or national. Farmers are often responsible stewards of their land, doing everything they can to take care of their land and animals while still making a living.

But the truth is that a farmer cannot manage what they don’t know, or don’t measure. And likewise, the opinions of the public are shaped mainly by commentary and hearsay. These new tools that the IoT has made possible will not only inform individual farmers and businesses as to their actual impact on the environment, it will enable to them to observe the patterns and make changes which can improve water quality and environmental conditions for all.

Adroit is excited to be part of this change and welcomes the opportunity to speak with individual farmers, community groups, regional authorities and Iwi about the tools available and how technology can play a part in the clean water solution.