Water is probably the most monitored feature of the New Zealand environment. Even so, national data are rather limited. Information on the quantity and quality of groundwater, surface water and coastal water are collected by a diverse range of organisations, headed by regional councils and local territorial authorities (i.e. district and city councils) and the National Institute of Water and Atmospheric Research (NIWA).
From 1983 through to 1988, the Ministry of Agriculture and Fisheries summarised much of the existing information on a region by region basis in a series of reports entitled "Regional modifications to waterways" in the now defunct journal, Freshwater Catch. Each report was authored by a scientist attached to either a government department or local authority and gave an overview of the history and impacts of water and land use in each of thirteen 'water regions' (Hicks, 1983; Davis, 1984; Richmond, 1984; Richardson, 1985; Rodway, 1986; Eldon, 1987; Watson, 1987; Poynter, 1987; Jellyman, 1984, 1988; Porter, 1988; Haughey, 1988; Boothroyd, 1988).
Apart from this, there have been few attempts to provide a systematic overview of the state of our waters, particularly at the national level. No repetitions of the 1980s baseline surveys have been undertaken to report on trends. At present, water monitoring tends to focus almost exclusively on the quantity and quality of water, and little on its ecological properties. Quantity is measured as stocks and flows (e.g. areas and volumes of lakes, rivers and groundwater, their flow rates, volumes and rates of rainfall and run-off, evaporation rates etc.). Quality is measured in terms of water clarity and the presence and degree of contamination (e.g. nutrient, chemical, and sediment content, and the concentrations and activity of micro-organisms). Water quantity is generally measured by hydrologists, while water quality is generally measured by chemists and biologists.
The ecological attributes of streams, rivers, lakes and wetlands have been only lightly monitored to date, partly because of a lack of standardised methods and partly because the emphasis in the past has been on monitoring water for human uses, rather than its inherent life supporting functions. As awareness of the ecological dimension grows, however, various methods are being investigated. One is the macro-invertebrate index which measures changes in the diversity and composition of the larger invertebrates in an area. Several different indices have been developed, and a few regional councils are now using one or other of these, but none is yet in widespread use. Another method is the indicator species approach, which monitors changes in the abundance or distribution of one or two selected species. At present, criteria for species selection vary widely.
A problem with ecological indicators is that they are difficult to interpret without a fairly sound knowledge of the ecosystem being monitored. Normal population fluctuations or species changes can be misinterpreted as signs of ecological degradation. It is also difficult to tell whether ecological trends in a monitored area apply to other areas. As a result, the ecological indicators tend to be used more as indicators of physical water quality rather than ecosystem health. Efforts are underway to resolve some of the difficulties with ecological monitoring through the Ministry for the Environment's National Environmental Indicators programme. A draft set of water quantity and quality indicators is being developed and work is progressing on ecological indicators. For now, though, any assessment of the state of our water environment is largely limited to measures of quantity and quality (see Box 7.1).
Knowing how much water is falling, flowing, and stored in New Zealand is important for agriculture, forestry, electricity generation, flood and erosion control, drought impact management, urban water supply, recreational use of rivers, and maintaining the habitat and biodiversity of fish and other stream and river life. New Zealand has an extensive network of river flow recording sites. Monitoring of river flows, lake levels, and rainfall began around the turn of the century. With the establishment of catchment boards in the 1940s, monitoring was extended so that flood and erosion risk could be assessed and, in the 1960s, it was expanded still further so that water could be better managed to take account of its allocation and conservation. Between 1959 and 1989 the number of permanent water level recording stations increased from 109 to 915 (Waugh, 1992).
Today, most monitoring of ground and surface water levels and river flows is undertaken by the successors to the catchment boards - regional councils and unitary authorities. Some of this information is fed into the National Hydrometric Network, which is coordinated by NIWA. In 1994, this network collected data from 231 sites including sites monitored by participating regional councils. Although economic factors led to a 20 percent reduction in the number of sites between 1993 and 1994, efforts have been made to maintain representative coverage, and even improve it in under-represented areas such as rainfall and flow monitoring in the less accessible parts of the Southern Alps (Mosley, 1993).
Several pollutants are of particular concern in New Zealand's surface and groundwaters. Suspended solids, micro-organisms, excessive nutrients, and chemical contamination can make water unsuitable for drinking, recreational use, or the health or survival of fish and aquatic ecosystems. Some pollutants can be measured directly, and some indirectly. Cost, ease of measurement, and degree of risk from particular pollutants are taken into account when deciding what to measure and where, when, and how. For example, micro-organisms can be measured directly by assessing the concentrations of particular algal and bacterial species in a sample of water, or indirectly by measuring biochemical oxygen demand (BOD5) which indicates the amount of oxygen consumed by micro-organisms and other decomposition processes as organic matter rots.
Suspended solids are particles of matter which float in water. They include inorganic sediments from rock and soil as well as organic matter. They can ruin fish habitat by reducing light, depleting invertebrate populations and degrading spawning areas. They can also reduce the drinkability and recreational use of water. Parameters (things which can be measured) that are related to suspended solids include visual water clarity andturbidity. Water clarity decreases when suspended solids increase. It is best measured as the sighting distance (in metres) of a black disk lowered on a rope into a stream or river, or a secchi disk (a black and white coloured disk) lowered into a lake. Turbidity (or muddiness) calculations are derived from the light scattering properties of water and sediment. Unfortunately turbidity is difficult to measure in absolute units, and the same water sample can give different results in different analytical machines. Turbidity is also relatively poorly correlated with suspended solids so, in general, water clarity measurements are considered a better method of assessing the optical quality of water (Ministry for the Environment, 1994).
Nutrients are vital for plant and animal health. However, an abundance of nitrogen (N) and phosphorus (P) (often referred to as nutrient enrichment) can fuel excessive plant and algal growth in rivers and estuaries (often referred to as eutrophication). Eutrophication may degrade surface waters by making them aesthetically unpleasant, by depleting the water's oxygen, by changing the quantity and type of food available for fish and birds, and by altering the habitat for fish and invertebrates. Dissolved reactive phosphorus (DRP) and dissolved inorganic nitrogen (DIN), which includes nitrate-nitrogen (NO3-N) and ammoniacal nitrogen (NH4-N), are most likely to cause excessive algal growths in waterways. In addition to nitrogen's eutrophication impact in waterways, ammonia can be toxic to fish, while nitrate can be toxic to humans and other animals that drink contaminated water.
Micro-organisms or microbes are minute organisms consisting of a single cell. They include simple bacteria (such as faecal coliforms, enterococci, and campylobacteria), and more complex one-celled organisms collectively known as protists (such as giardia, cryptosporidium, amoebae, and micro-algae). The micro-algae may be free-floating 'blooms' or slimy coatings (periphyton) on rocks. Fungi are also sometimes included among the micro-organisms although the true fungi are actually multi-cellular organisms, occupying their own large kingdom between the plant and animal kingdoms. Some fungi and micro-organisms can cause illness in humans who eat contaminated shellfish or who swallow contaminated water while swimming, boating, fishing etc. It is not practical to monitor all the potentially harmful organisms in water so a few indicator organisms are monitored instead.
Faecal coliforms are the most commonly used indicator of microbial contamination. Where concentrations of faecal coliform bacteria are high (measured as the number of faecal coliforms in 100 millilitres of water) the risk of harmful organisms being present is also assumed to be high. Biochemical oxygen demand (BOD5) is another indicator of microbial contamination. It measures the amount of oxygen in a water sample that is consumed over a five-day test period by the micro-organisms and biochemical processes that break down rotting organic matter. BOD5 increases with the amount of dead organic material in water, and indicates the potential for algal growths and depletion of dissolved oxygen. Dissolved oxygen (DO) is a direct measure of the amount of dissolved oxygen in water (expressed in grams of oxygen per cubic metre of water, or g/m3). DO is particularly important to ensure the survival of aquatic animals. DO varies considerably and is usually lowest around day-break. Because of the variability of DO levels, sampling needs to be careful and interpretation of DO data requires caution.
Chemical contaminants in water are mostly metals and organic substances. Metals, such as arsenic, mercury, lead, zinc and copper can enter waterways from industrial sites, rubbish tips, motor vehicles and geothermal areas. Small amounts can accumulate to toxic levels in shellfish, fish and marine mammals, and large amounts can reach toxic concentrations in the water itself. Metal contamination in sediment and water is usually measured as the concentration of the particular metal in a volume of water (e.g. grams, milligrams or micrograms per cubic metre) or in a kilogram of sediment.
Toxic organic substances in water can include oil, petroleum products, pesticides (including wood preservatives), some plastic compounds and industrial chemicals, and their break-down products. Some are carcinogenic, and others are suspected of being environmental oestrogens, interfering with the body's normal hormonal balance. They may enter water (including groundwater) through a variety of sources, such as spills, failures in pipes and storage facilities, as leachate or run-off from landfills or contaminated sites, through stormwater systems, and by inappropriate pesticide applications. Many petroleum and other oil products are insoluble and float on the surface of water and may stick to plants and animals. However, a proportion of toxic organic substances are soluble, and may become invisible once they enter the water.
Units of measurement vary considerably for the different water monitoring parameters. However, the unit that is most familiar to the general public, the litre, is rarely used. While it may be ideal for measuring small amounts of liquid, such as our daily supplies of petrol, oil, and milk, the litre is simply too small to cope with the quantities of water that hydrologists measure. Instead, they deal in cubic metres (m3 ), million cubic metres (Mm3 ), and even cubic kilometres (km3 ). One cubic metre is a thousand litres. A million cubic metres is a billion litres. And a cubic kilometre contains 1,000 billion (i.e. a trillion) litres. Water flow is often measured in cubic metres per second (m3/s) or cumecs, which are equivalent to a 1,000 litres per second (l/s).
The variety of measurement units increases when water quality is being monitored. Quality is often expressed as the amount of a given contaminant per measure of water, for example parts per million (ppm) or parts per billion (ppb), or grams per cubic metre (g/ m3) which can also be expressed as milligrams per litre (mg/l) or micrograms per millilitre (µg/ml). Water quality can also be measured in many other ways, however, such as biochemical oxygen demand (BOD5) which is the amountof dissolved oxygen consumed over 5 days by the decomposition of organic matter (expressed, in water, as grams per cubic metre, or BOD5/g/ m3, or, in animal excrement, as kilograms per day, or BOD5/kg/day ); microbial concentrations (expressed as organisms per 100 millilitres ); visual clarity range (expressed in metres ); turbidity (expressed in nephelometric turbidity units or NTUs) ; and acidity/alkalinity or softness/hardness (expressed as pH or proportion of hydrogen ions).
Knowing whether water is polluted is important for anyone intending to drink, swim, eat shellfish, or provide water for livestock. It is also important for ensuring the survival of fish and other aquatic life. Water quality monitoring began relatively recently, mostly within the past decade, as desk computers made it possible to store and analyse the information easily (Waugh, 1991). Now most regional councils have water quality monitoring programmes for both surface water and groundwater (including geothermal water where applicable).
Not all the monitoring is at the local level. Limited national data are available from the '100 Rivers Study' which surveyed a large sample of rivers from 1987 to 1990 (Close and Davies-Colley, 1990), and the National Water Quality Network (NWQN) which has conducted a monthly survey of 77 rivers and streams and 16 shallow lakes since 1990 (Smith and McBride, 1990; Burns, 1994). These surveys were initiated by the former Department of Scientific and Industrial Research (DSIR) and are now NIWA's responsibility. For cost and logistical reasons, the NWQN does not monitor water quality in large lakes. Nor does it monitor microbial water quality (see Table 7.1).
Another national monitoring exercise is the National Groundwater Monitoring Programme which was initiated in 1992 as a cooperative project between some regional councils and the Institute of Geological and Nuclear Sciences Ltd. Most regional and unitary authorities now participate in the programme. Every four months the participating local authorities supply groundwater samples to the Institute of Geological and Nuclear Sciences for analysis, the results of which are then collated into a database (see Table 7.2).
|Parameter||Where measured||River or lake||Why the parameter is monitored|
|Dissolved Oxygen (DO)||field||R/L||Necessary for aquatic life; rapid indicator of pollution; indicator of lake trophic state.|
|Biochemical oxygen demand (BOD5)||lab||R/L||Indicates decomposing organic matter by measuring the amount of dissolved oxygen used by micro-organisms and biochemical processes.|
|Conductivity||lab||R/L||Simple measure of dissolved inorganic chemical ions.|
|Temperature||field||R/L||Necessary to interpret dissolved oxygen data; mixing of lake currents; protection of aquatic life.|
|pH (acidity/alkalinity)||lab||R/L||Protection of aquatic life; pollution indicator.|
|Visual clarity||Descriptive standards; visual indicators of water quality effects of sediment, algae etc|
|Turbidity and Light Absorption coefficients||lab||R/L||Turbidity coefficient complements visual clarity measurements; light absorption coefficient relates to colour and organic content of water.|
|Total nutrients||Nutrient status of water; potential for algal growth.|
|Dissolved nutrients||lab||R/L||Drinking water standards; nutrient status of water; potential for algal growth.|
To establish relationships between river flow and water quality.
|Lake level||field||L|| |
To establish relationships between lake level and water quality.
|Chlorophyll a||lab||L|| |
Indicator of algal density, showing nutrient status; indicator of water use change.
|Benthic invertebrates||lab||R|| |
Indicator of water use change.
|Nuisance periphyton growth||field||R|| |
Visual indicator of water quality.
|Parameter||Where measured||Why the parameter is monitored|
|pH (acidity/alkalinity)||field||Helps determine environmental influences (soil and rock types, source of water, pollution) on ground water chemistry.|
|Temperature||field||General description - helps assess significance of dissolved substances.|
|Conductivity||field||Simple measure of total quantity of dissolved inorganic chemicals.|
|Major cations (e.g. calcium, magnesium)||lab||General description of groundwater quality, to determine environmental influences (soil and rock type, water source, pollution) on groundwater composition; numerical drinking water standards.|
|Major anions (e.g. chloride, sulphate)||lab||General description of groundwater quality, to determine environmental influences (soil and rock type, water source, pollution) on groundwater composition; numerical drinking water standards.|
|Trace metals||lab||Indicator of source of groundwater (e.g. geothermal); numerical drinking water standards.|
|Dissolved nutrients |
|lab||Indicator of groundwater contamination; numerical drinking water standards.|
|Groundwater levels||field||To establish relationships between groundwater levels and water quality.|
Precipitation results in 580 cubic kilometres of water falling to the ground. At the surface, 53 cubic kilometres of water is held in snow and ice; 320 cubic kilometres in lakes; and 415 cubic kilometres in rivers. 205 cubic kilometres of water is infiltrated into groundwater aquifers in the soil, moving out to the ocean. 165 cubic kilometres of water is evaporated from the surface, forming clouds of water vapour.
Source: Adapted fom Mosley (1993)
Most regional councils have, or are developing, coastal monitoring programmes which measure sediment movement and coastal erosion, water levels in coastal and estuarine areas, and bacterial concentrations in the water at bathing beaches, around sewage and stormwater outfalls, and around shellfish beds. In some places, limited monitoring of sediment quality has also been undertaken.
The Ministry of Agriculture's Marine Biotoxins Surveillance Unit, until its recent disbandment, monitored an average of 120 shellfish samples from sites around New Zealand each week for signs of contamination by toxic algae. The Ministries of Agriculture and Health now share responsibility for monitoring toxic algae. Limited environmental data on salinity, water temperature and clarity, daylight and sea conditions are also collected to help identify factors that may trigger toxic algal blooms.
Drinking water quality is monitored by the authorities in charge of water supplies and the results are collated through the Ministry of Health's Drinking Water Surveillance Programme
Marine and freshwater ecosystems have been widely studied but rarely monitored in a systematic way. The main databases on them are held by NIWA (e.g. the freshwater fish database, which is updated twice a year, and a large amount of marine biodiversity data, much of which has not yet been collated). The Department of Conservation also holds data (e.g. the WERI database on Wetlands of Ecological and Regional Importance, which is not regularly updated, and the Coastal Resource Inventory, which is more descriptive than quantitative). University scientists, and some regional councils, also hold data on aquatic ecosystems, though often the focus is limited to a particular species, location, or time period, making it of limited value in assessing national trends. Quantitative data on ecological processes are particularly rare.
In most parts of the North Island average annual rainfall is 1200 to 2400 mm. In the South Island, the West Coast is wet or very wet (2400 mm to 3200 mm or more rainfall annually) while the east coast is dry (400 to 1200 mm annually).
Source: NZ Meteorological Service
In the South Island, the east coast has limited surface water. In the North Island there is limited surface water along the east coast, going through to the west coast in the area between Levin and Wanganui. There is also limited surface water through most the north of the North Island.
Adapted from Pearson (1995)