It is extremely disappointing that this data is so out of date, given the concern that many NZers have expressed about the declining water quality in NZ. This decline has been documented by many other Government organisations such as NIWA and the Parliamentary Commissioner for the Environment.
- Concentrations of phosphorus, bacteria, and ammonia were either stable or improving at most monitored sites.
- Nitrate concentrations and macroinvertebrate condition (water insect life) deteriorated at more sites than improved. High concentrations of nitrate can cause excessive aquatic plant growth and are toxic to fish. The composition of macroinvertebrate communities reflects changes in water quality, river habitat, and catchment condition.
NIWA: The declining water quality in our rivers and lakes will get worse
Status and trends in water quality – NIWASustained national-scale monitoring is fundamental to determining the state of our freshwaters, the impacts of land use changes, and the success of clean-up efforts. The country’s only national-scale monitoring programme, the National Rivers Water Quality Network (NRWQN), is operated by NIWA. The network regularly samples 77 sites, including 35 major rivers that drain 50 percent of our land area.Trends in NRWQN data between 1989 and 2007 (published on the MfE website) show an overall degradation in water quality in our major rivers. Over that period, nitrogen and phosphorus – key plant nutrients added in fertilisers – increased strongly at many sites. Nitrogen increased by about 1.4 percent per annum over most of the country, but remained steady at pristine sites like the Haast River; no sites recorded a drop in nitrogen concentrations (see map).Water quality is appreciably worse at several hundred sites in lowland rivers monitored by regional councils – many rivers show excessive nutrients, reduced visual clarity due to suspended sediments, and pollution by faecal bacteria.
Ministry of the Environment: Intensive land use lowers water quality
The amount of nitrogen in rivers is going to get worse …The modelling shows annual nitrogen loads on fresh water continuing to rise in virtually every region. Figure 7.1 shows how these increasing nitrogen loads correlate with the expansion of dairy farming. Canterbury, Southland, and to a lesser extent, Otago, stand out. Other regions have lesser increases, although some, such as Waikato and Manawatū, already have high nitrogen loads and existing water quality problems.
New Zealand Herald: 48% of rivers unsuitable for swimming
Does it matter if we can only swim in our waterways some of the time?
Aquatic life needs needs very high water quality
The case for the Long fin eels
Too much sediment:
- Clear flowing streams with shaded stony beds – a favoured habitat for longfin eels – became open to the sun and smothered in sediment.
- Without roots and overhanging branches, longfin eels lost the shelter and holes in which they made their homes.
Too many nutrients:
- Irrigation often leads to more intensive land use, frequently resulting in greater concentrations of nutrients and sediment in the water, and thus poorer water quality.
- It is not the nutrient and sediment levels themselves that are the main problem for eels, who are quite resilient creatures. However the ensuing excessive plant growth can smother the stream bed, reducing both habitat and food for eels and other fish.34 Sometimes toxic algae bloom, which while not killing eels directly, have made eels poisonous to eat.
17% of Waikato’s horticultural soils already exceed 1 mg/kg soil cadmium
Conservatively, the average cadmium concentration in Waikato dairy soils is projected to reach the recommended guideline in under 16 years.
Dr Nick Kim\’s report, mentioned above, looks specifically at the issue of Cadmium in Waikato soils. The current status of Waikato’s productive soils is succinctly stated in the executive summary:Based on recent sampling, it is estimated that perhaps 11% of Waikato’s pastoral soils and 17% of Waikato’s horticultural soils already exceed 1 mg/kg soil cadmium. For horticultural soils, this would represent approximately 1775 hectares of land. For pastoral soils (sheep, beef and dairy land), this would represent about 157000 hectares. Within the pastoral soils sample set, all soil samples that have so far exceeded the 1 mg/kg agricultural guideline have been from dairy farms.On average, Waikato’s productive pastoral, horticultural and arable surface soils now contain five times more cadmium than they began with, and are two-thirds of the way to the 1 mg/kg threshold.Loading calculations confirm that the dominant source of this cadmium is superphosphate fertiliser, which contains cadmium as an impurity. Projections for pastoral and horticultural soilsAt current cadmium loading rates, the next significant point at which the 1 mg/kg cadmium guideline will be reached over wide land areas is expected for dairy farms, which cover about 25% of the Waikato region (about 623000 hectares).
Quick facts about Cadmium
- Heavy metal with a high toxicity.
- Toxic at very low exposure levels and has acute and chronic effects on health and environment.
- not degradable in nature and will thus, once released to the environment, stay in circulation. New releases add to the already existing deposits of cadmium in the environment.
- Cadmium and cadmium compounds are, compared to other heavy metals, relatively water soluble. They are therefore also more mobile in e.g. soil, generally more bioavailable and tend to bioaccumulate.
Effect on ecosystem
- Cadmium is readily accumulated by many organisms, particularly by microorganisms and molluscs where the bioconcentration factors are in the order of thousands.
- Soil invertebrates also concentrate cadmium markedly.
- In animals, cadmium concentrates in the internal organs rather than in muscle or fat. It is typically higher in kidney than in liver, and higher in liver than in muscle. Cadmium levels usually increase with age. (In New Zealand as at 2002 the offal of animals older than 2.5 years was not permitted to be sold for human consumption for this reason. Dr Nick Kim Cadmium Accumulation in Waikato Soils – Environment Waikato 2005)
A major part of cadmium in the human diet comes from agricultural products.
- The most important sources of cadmium to agricultural soils are atmospheric deposition and direct inputs through, for example, the application of phosphate fertilizers and other soil amendment products.
- Some of the regulative focal points in many countries have being decreasing the cadmium content of fertilisers and restriction on the input of cadmium to farmland by application of sewage sludge and other waste products.
- Cadmium accumulates in the human body and especially in the kidneys. According to the current knowledge kidney damage (renal tubular damage) is probably the critical health effect, both in the general population and in occupational exposed workers /Järup et al 1998/.