Maintaining good water quality is important for healthy ecosystems and healthy humans. There are several national, regional and local government agencies that look after water quality:
- The Ministry for the Environment has national water quality guidelines to protect ecosystems and aquatic life. It also has guidelines to protect human health and safety while swimming or participating in freshwater recreational activities.
- The Ministry of Health has national guidelines for drinking water.
- Regional and district councils issue resource consents that permit the use of water and the safe discharge of water or waste into water sources.
- The agencies also take into consideration the Treaty of Waitangi and the special relationship Māori have with land, water and natural resources.
Water quality monitoring provides the evidence needed to show whether water is suitable for human use and swimmability, whether it is suitable for local ecosystems and whether users are meeting the conditions of their resource consents. Individuals and community groups also monitor water quality to seek evidence that ecosystem restoration practices are successful. How often monitoring is carried out and what aspects of water quality are monitored varies between those who are collecting the data, but monitoring protocols are usually similar.
Nature of science
Water quality monitoring provides empirical evidence about physical, chemical and biological aspects of a body of water. It is the role of science to provide the evidence, but it is the role of regulators to use this information when making decisions about human and environmental health.
New Zealand’s regional councils regularly monitor the suitability of water for human use and ecological health. Waikato Regional Council (WRC) makes monthly water quality measurements at 115 river and stream sites including the Waikato, Waipā, Waihou and Piako Rivers and at 13 sites in and around Lake Taupō. According to WRC water scientist Dr Eloise Ryan, the council monitors around 32 indicators of water quality each month.
The council uses seven indicators to determine whether the water is passable for ecological health and two additional indicators (baseflow water clarity and E. coli) to determine whether it is passable for human recreational use.
These are the indicators that are measured:
- Dissolved oxygen: Fish and other aquatic life require oxygen for respiration. Low levels of dissolved oxygen may indicate large numbers of aquatic plants.
- pH: The pH range suitable for aquatic plants and animals is 6.5–9. Very high or very low pH makes the water toxic for things living in it.
- Turbidity: Turbidity reflects the amount of sediment suspended in the water. Murky water reduces the amount of sunlight available to plants to photosynthesise, makes it difficult for creatures to see their prey and makes swimming uncomfortable for humans.
- Total ammonia: Too much ammonia is toxic to aquatic life. Ammonia enters waterways via wastewater or from animal wastes.
- Temperature: Just like humans, fish and other aquatic life depend on suitable temperatures. Water temperature varies with climate, but the lack of vegetation cover and industry discharges of heated water used for cooling affect water temperature.
- Total phosphorus: Phosphorus is a nutrient that supports plant growth including nuisance aquatic plants that clog waterways and displace native plant species. Phosphorus enters waterways via wastewater or agricultural run-off.
- Total nitrogen: Nitrogen is a nutrient that supports plant growth including nuisance aquatic plants that clog waterways and displace native plant species. Nitrogen enters waterways via wastewater or agricultural run-off.
- Baseflow water clarity: Water clarity and underwater visibility are important for swimmers and others who use the water – for safety and because we like the look of clear water.
- Escherichia coli: E. coli bacteria are harmful microorganisms sometimes present in water. They enter the water via wastewater (human faeces) or agricultural run-off (animal faeces).
Water is a key resource for primary industries such as horticulture and agriculture. Regional councils have regulations for the allocation and use of water and for the discharge of water containing nutrients, sediments and farm animal effluent. However, for many farmers and growers, the effort to protect water quality goes beyond the need to keep within resource consents.
Waikato dairy farmers Rod and Sandra McKinnon test the water coming into and out of their 194 ha Hinuera property for E. coli, turbidity, phosphorus and nitrogen. There are no legal requirements for them to do this. Sandra and Rod monitor the water to see if the changes they’ve made to their management practices are working. Rod says that 5 years of monitoring show the positive results from riparian stream planting, an upgraded effluent system and careful stock management.
A S Wilcox & Sons grow potatoes, carrots and onions for New Zealand and overseas markets. The company has farms from Northland to Canterbury. The growers have innovative systems to ensure they use their allocation of water wisely and that nutrients and sediments don’t end up in local waterways. Senior crop manager Bryan Hart says that his company performs a series of water quality tests as part of their ongoing catchment management and as part of New Zealand Good Agricultural Practice (NZGAP) accreditation.
Hamilton’s Fairfield Project works with schools and the community to protect and restore an urban gully ecosystem and the Kukutāruhe Stream – a small stream that runs into the Waikato River. A team from the National Institute of Water and Atmospheric Research (NIWA) has been monitoring the stream for many years to study the giant kōkopu living in it. Educator Lynnette Rogers and local school students also conduct water quality monitoring. They’ve been restoring the riparian edges of the stream and using the area as a contextual, outdoor classroom. One thing they’ve learned is that restoration is a long-term process – it takes time to turn around an area that’s been neglected for years.
The article Water quality looks at some of the factors that affect water quality, including where the water comes from, what is in the environment in the collection area and how it is treated for human consumption.
The farming management practices discussed in this article help farmers minimise the effects of nutrient leaching and run-off and reduce sediment loss from paddocks.
Find out more about the importance of riparian restoration, and in the article Planting stream edges, find out why riparian restoration is so important to our freshwater native fish and the three steps to take for riparian planting planning.
In Water quality in Rotorua lakes, learn how Professor David Hamilton studied 12 Rotorua lakes in order to discover how land use affects water quality and what might be done to preserve or restore water quality in the lakes.
This article has been developed in partnership with the Waikato Regional Council as part of the Rivers and Us resource.