Waterway Pollution: Nz's Battle Against Contamination

Water pollution in New Zealand is a growing concern for those who use and care for the country's waterways, as well as for regulatory bodies. The main causes of waterway pollution in New Zealand are diffuse (or non-point) source pollution, which includes agricultural production and intensive land use, particularly pastoral and dairy farming. Other sources of pollution include urban runoff, industrial discharges, and excess nutrients, which can lead to eutrophication and toxic algal blooms. Natural causes, such as rotting vegetation and stagnant water, can also contribute to waterway pollution.

Dairy farming

First, the high number of cows means an increase in fertiliser, irrigation, and supplementary food. Since 1990, the amount of nitrogen applied to the land has increased by 629%, from 62,000 to 452,000 tonnes. This has led to an increase in nitrate and pollution in the water systems. More cows also mean more hooves walking through waterways, stirring up sediment.

Second, cows produce a lot of urine and faeces, which can contaminate waterways. This, along with excess chemicals from fertiliser for their feed, can leach into waterways.

Third, dairy farming can lead to eutrophication, or an increase in nutrients in waterways, which can have harmful effects. For example, it can cause blooms of specific species of algae that produce toxins. This can be fatal to aquatic creatures and render water unfit for consumption or contact recreation. Avian botulism is derived from bacteria that thrive in anoxic conditions, and it kills birds in lakes during New Zealand summers.

Finally, dairy farming can also impact water quality through runoff. Phosphorus, for example, can run off from pasture or urban areas into waterways, impacting water quality.

In response to concerns about water pollution from dairy farming, Fonterra, New Zealand's largest dairy company, along with several government agencies, instigated the Dairying and Clean Streams Accord. The aim of the Accord is to limit the access of stock to waterways and reduce pollution from surface runoff. Regional councils have also imposed more regulatory requirements on farmers to reduce their environmental impacts, such as requiring Farm Environment Plans and imposing nutrient limits.

Urban runoff

One of the primary concerns with urban runoff is the high levels of nutrients, particularly nitrates, that are washed into waterways. These nutrients can come from a variety of sources, including lawn fertilisers, car exhaust, and industrial waste. When excess nutrients enter rivers and lakes, they can cause eutrophication, leading to algal blooms and oxygen depletion. This has severe ecological consequences, including fish kills and the disruption of food chains. In some cases, it can also render water unfit for human consumption, posing health risks to those who rely on these water sources.

The effects of urban runoff are particularly evident in urban rivers, which are generally the most polluted waterways in New Zealand. A 2017 report found that water quality was worse in low-elevation areas, including the Auckland region, where 62% of rivers and lakes were graded as poor for swimming. Nitrate-nitrogen concentrations are worsening at more monitored sites, and E. coli concentrations are affecting swimming safety in rivers.

To address the issue of urban runoff, New Zealand has implemented various measures. These include increasing regulatory requirements on urban developments to reduce their environmental impacts and improve stormwater management. Additionally, there are over 800 water quality monitoring sites across the country that help identify and address pollution sources. However, the country's reputation as an "unspoilt wilderness" has made it challenging to acknowledge and address the extent of the pollution problem, particularly regarding the powerful dairy industry.

Industrial discharges

One of the key issues associated with industrial discharges is the release of excess nutrients into waterways, particularly in lowland areas. Nitrate-nitrogen concentrations are on the rise, and E. coli levels are affecting the ability to swim in rivers safely. These nutrient pollutants can have severe ecological consequences, including fish kills and the disruption of food chains. High levels of nutrients, particularly nitrates, can also contribute to algal blooms, which can produce toxins fatal to aquatic life and render water unsafe for human consumption or recreational use.

In addition to nutrient pollution, industrial discharges can introduce other contaminants into water systems. For example, faecal pathogens and pesticides may be present in industrial wastewater, posing significant risks to human health if they reach water sources used for drinking or recreation. Poor farming practices and inefficient waste management systems can contribute to the presence of harmful bacteria such as campylobacter, typhoid, giardia, and cryptosporidium in waterways.

Furthermore, industrial discharges can also impact sedimentation patterns in waterways. Sediment from erosion, intensified by land use practices such as farming and urban development, can carry high organic content from forest litter. This changes fluvial systems, increasing sediment deposition in lakes and coastal waters.

To address the issue of industrial discharges, regulatory bodies in New Zealand have imposed stricter requirements on industries to reduce their environmental impacts. These measures include implementing Farm Environment Plans, imposing nutrient limits, and encouraging sustainable practices to reduce fertilizer use and intercept runoff.

Erosion

The effects of erosion on water quality are wide-ranging. Firstly, it reduces water quality by increasing turbidity (cloudiness), which decreases light penetration. This has adverse consequences for fish diversity, food supply, and recreational use of waterways. Additionally, erosion can lead to the deposition of soil and sediment in lowland areas and streams, causing infrastructure damage, including roads, drains, houses, fences, and power lines.

To address erosion and its impact on water pollution, regional councils in New Zealand have implemented various measures. Environment Canterbury, Horizons Regional Council, and Hawke's Bay Regional Council require farms to have Farm Environment Plans, which include strategies for managing environmental risks such as erosion and discharges into waterways through planting and fencing. The Manawatū plan encourages hill country farmers to plant trees across thousands of hectares, offering government subsidies to support this initiative.

Controlling animal pests is another important aspect of reducing erosion caused by farming. For example, Molesworth Station in Marlborough transitioned from sheep to beef cattle, which helped control rabbit invasions and supported the revegetation of depleted hill country. Mechanical methods, such as flumes, debris dams, and detention dams, are also employed to control and prevent erosion on farmland.

Horticulture

One of the main ways is through the erosion of hills and river banks, which causes sediment to enter waterways. This sediment can contain high levels of organic content from forest litter, which can change sedimentation patterns and increase organic bed loads and deposition in lakes and shallow coastal waters. Horticulture practices that expose the soil, such as tilling, can increase the vulnerability of the soil to erosion, particularly during periods of high rainfall or flooding.

Another way that horticulture can impact waterway pollution is through the use of pesticides and fertilizers. If these chemicals are not used properly, they can wash into nearby waterways, causing pollution and harming aquatic ecosystems. Additionally, the use of irrigation in horticulture can also impact waterway pollution if the water is not properly managed and treated before being returned to natural water bodies.

To mitigate these impacts, farmers in New Zealand are encouraged to adopt good management practices, such as excluding stock from waterways, reducing contaminants, and implementing riparian planting. Riparian vegetation, such as trees and long grass, can help to stabilize soil and reduce the amount of sediment entering waterways. It also provides shade, which can regulate water temperature and reduce weed growth. These measures not only improve waterway health but also benefit the surrounding environment and communities.

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