12. Surface Water Quality

 

Summary

RPS Objectives

· The maintenance and enhancement of the water quality in lakes, rivers and streams to be suitable, in the long term, for the following purposes as may be appropriate; aquatic ecosystems, contact recreation, water supplies, aesthetic and cultural purposes.

· The reduction in the quantity of contaminants that impact on water quality entering lakes, rivers and streams.

Pressures

· The number of consented discharges to water and to land, where it can reach water, has steadily increased in the last 10 years, with more than 2200 discharge consents in January 2007.

· The percentage of significant non-compliance for industrial discharges increased between 2003 and 2006, however there was no significant non-compliance reported out of 163 site visits in 2006/2007.

· It is estimated that there are approximately 20,000 on-site wastewater systems in Northland, servicing around 30% of the population, which can have a detrimental effect on water quality if poorly maintained or designed. There are still several community wastewater sewerage systems that require upgrades to meet consent conditions.

· People are often not aware that stormwater is usually discharged directly to our water bodies without treatment and even a very small quantity of some pollutants in stormwater can drastically alter the quality of the receiving waters.

· Non-point source pollution including animal excreta, sediments, nutrients and other pollutants from the surface of the land during rainfall. With 50% of Northland land area in pasture, agricultural land use is a major source of non-point source pollution.

· An increase in the use of higher intensity farm practices in the dairy industry such as feed pads and imported supplementary feed has allowed the number of cows per hectare to increase.

State

· In most summers, at least a quarter of the freshwater swimming spots sampled are generally safe for recreational use, while at least a quarter have typically poor water quality that is frequently not safe for swimming. The River Water Quality Monitoring Network (RWQMN) sites are similar to the recreational bathing sites, with approximately a third often not suitable for swimming

· Only one of the 21 RWQMN sites comply with the guideline range for dissolved oxygen on more than 50% of sampling occasions.

· Mangere Stream has the highest nutrient levels of the 21 RWQMN sites for 2006. Sites with mostly native forest or exotic forest in their upstream catchments have the lowest nutrient levels such as Victoria, Waipapa, Waipoua and Opouteke River sites and Mangahahuru Stream at Main Road.

· Sediment sampling in a Whangarei urban catchment shows that for most heavy metals there is very little difference between upstream and downstream of the urban area. However, both lead and zinc have been slightly higher downstream.

· Macroinvertebrate monitoring indicated clean water at two of 24 sites monitored in 2007, the two native forest sites: Waipapa at Puketi forest and Waipoua at SH12, while five sites had macroinvertebrate communities indicative of severe organic pollution: Waitangi at Watea, Mangahahuru at Apotu Rd, Mangere, Waiotu and Kaihu

· Several RWQMN sites have shown positive trends such as decreasing nutrient levels or increasing water clarity, which suggests there have been improvements in point source discharges. However some RWQMN sites have also shown negative trends such as increasing dissolved oxygen, bacterial and nutrient levels.

· The bacterial levels only meet the recommended guidelines for stock drinking water at four of 37 different sites.

Doing well

· The Regional and District Councils have several initiatives underway to improve wastewater treatment and minimise the effects on Northland's environment, such as treatment plant upgrades and the development of risk maps for the region.

· State of the Environment monitoring and analysis to assess the state and changes of freshwater quality through time.

· Public awareness and education through workshops and field days with school, environmental care, industry, iwi and landowner groups.

Areas for improvement

· Investigations into areas identified as having water quality problems, including the use of more advanced water quality monitoring techniques.

· The region's knowledge of freshwater biodiversity, particularly the extent of native and pest fish.

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Published: 03 Apr 2008