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Data collection, analyses, and limitations

For the analyses in this report, we collected information from many sources. This report would not be possible without the ongoing support and contribution of a large number of people and organisations.

The water quality information largely comes from regional and unitary councils, NIWA, and GNS monitoring networks. For the regional council networks in particular, many monitored sites tend to be in areas of known, or suspected, issues so that regional councils can make management decisions; however, this potentially leads to a biased view of national water quality. To overcome this issue, we used modelled water quality data to estimate water quality in areas where we do not have data. We also use models to estimate nitrate leaching and periphyton growth, to help us build the story around water quality pressures and impacts. We currently have limited data on the pressures and impacts related to water quality, particularly monitored data at a national scale.

The chapter on water quantity focuses on information about consents to take fresh water, which was supplied by all 16 regional and unitary councils. We rely on consent information, because actual data on water use is not yet available nationally. However, the water metering regulations introduced in 2010, and which were fully in force in November 2016, will allow us to report on more actual water use data over time. We currently have very little data in this report on the state of freshwater flows compared with natural levels, and the impact any altered flows are having on freshwater ecosystems and species.

In the ecosystems, habitats, and species chapter, information comes from a wide range of sources including regional councils, Crown research institutes, Cawthron Institute, and Department of Conservation. There is little national data, collected over a period of time, on ecosystems, habitats, and species. Exceptions include the conservation status of plants, fish, and invertebrates from the Department of Conservation, and the New Zealand Freshwater Fish Database administered by NIWA. As with the other two chapters, data on the pressures and impacts on our ecosystems, habitats, and species are limited.

Environmental issues, by their nature, are specific to catchments or regions. New Zealand has a diverse range of river systems, lake types, wetlands, and groundwater systems. The state of fresh water depends on, for example, the physical characteristics of the water body and catchment, historical impacts, and how the land was used in the catchment (including the extent or intensity of this use). Although some of New Zealand’s freshwater bodies and their surrounding catchments were studied extensively, we know little about others. We aim to continue to build on a national picture of the pressures on our fresh water, the state of fresh water, and the impact the state is having on our ecosystems and our well-being.