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Water Quality Glossary
Contact Recreation
Recreation that involves a person immersing there head under water eg swimming, water skiing and whitewater kayaking.
Dissolved Oxygen
Dissolved oxygen is important for fish and other aquatic life to breathe. Water should be greater than 80 percent saturated with dissolved oxygen for aquatic plants and animals to live in it. Low levels of dissolved oxygen in rivers, such as the Motupipi, often indicate the presence of large numbers of aquatic plants, especially in small streams.
E. coli (Escherichia coli)
E. coli bacteria are used as an indicator of the human health risk from harmful micro-organisms present in water, for example, from human or animal faeces. Most E. coli strains are harmless, but some, such as serotype O157:H7, can cause serious food poisoning in humans.
Faecal Coliforms
A group of bacteria, that includes E.coli, that is found in faeces of warm-blooded animals. Also used as an indicator of human health risk.
Filamentous Algae Cover
Filamentous algae grows in long (<2cm) strands on the stream bed. Such algae grows in greatest abundance in conditions of abundant light, nutrients and stable stream flow. If the total percent cover of this algae gets over 30%, then it is likely there are excessive nutrients discharging to the waterway.
Leaching
A process by which chemicals in the soil (especially the plant nutrient nitrogen), are moved out of the soil by water.
Macro-invertebrates
Invertebrates are organisms without an internal skeleton such as insects, worms, shellfish, crustacean. Macro-invertebrates are these organisms that are clearly visible using low magnification microscopes.
Mauri
All living things have mauri, which is interpreted here as the waterway's vital essence, or life force. A highly degraded waterway will have very little mauri but by introducing wetlands, riparian planting and improved land management we can contribute to an enhancements of the life sustaining qualities of the water.
Median
The median number of E. coli bacteria present in water samples should be less than 126 per 100 millilitres of water if it is to be used for recreation.
Non-point source discharges
Discharges of contaminants that do not come from a single place, such as an industrial site, or from a specific outlet, such as a pipe. Some sources of non-point source discharge include run-off from agriculture, forestry and urban areas (for example, stormwater and construction sites).
Point source discharges
Discharges of contaminants that come from a stationary or fixed facility, for example, from a pipe, ditch or drain.
pH
pH is a measure of the acidity or alkalinity of water. A very high or very low pH means that water can be toxic for aquatic life. The pH range that is suitable for aquatic plants and animals is 6.5 – 9. In Tasman District pH is very seldom an issue.
Run-off
Water that runs off the surface of the land, and flows into waterways.
Run-off can contain:
- Sediment
- Phosphorus
- Nitrogen (however, most nitrogen enters waterways through leaching)
- Faecal matter – bacteria and viruses
Single sample
The maximum number of E. coli bacteria present in any single water sample should be less than 550 per 100 millilitres of water.
Temperature
Water temperature is important for fish spawning and aquatic life. Between May and September, when trout are spawning, water should be less than 12°C. Between October and April, water should be less than 20°C for general trout health and less than 25°C for most native fish. Water temperature is affected by climate and by discharges of cooling water from industry. Temperatures are naturally higher in the Waimea-Moutere area due to higher sunshine hours.
Total ammonia
High levels of ammonia are toxic to aquatic life, especially fish. The level of total ammonia in water should be less than 0.88 grams per cubic metre to be safe for fish. Ammonia in waterways comes from either wastewater or animal wastes (dung and urine).
Total nitrogen
Nitrogen is a nutrient that can encourage the growth of nuisance aquatic plants. These plants can choke up waterways and out-compete native species. High levels of nitrogen in water can be a result of run-off and leaching from agricultural land. Ideally, total nitrogen levels in water should be less than 0.5 grams per cubic metre to prevent excessive growth of nuisance plants. Non-point sources of nitrogen are the major contributors of nitrogen to waterways.
Total phosphorus
Phosphorus is a nutrient that can encourage the growth of nuisance aquatic plants. These plants can choke up waterways and out-compete native species. High levels of phosphorus in water can be a result of either wastewater, or, more often, run-off from agricultural land. Ideally, total phosphorus levels in water should be less than 0.04 grams per cubic metre to prevent excessive growth of nuisance plants.
Turbidity
Turbidity is a measure of the murkiness of water, reflecting the amount of sediment in the water. High turbidity reduces the amount of light available to the plants and animals living in the water. It reduces the ability of plants to photosynthesise. It also makes it difficult for fish and other animals to see their prey. Turbidity should be less than 5 NTU (turbidity measurement scale) for water to support plant growth.
Water clarity
Water clarity and underwater visibility is important for recreation such as swimming and waterskiing. It is also important from an aesthetic point of view – most people prefer to see clear water in our rivers and streams. To allow good visibility for swimming, you should be able to see at least 1.6 metres underwater.
Water clarity is measured by sighting a black disc attached to a tape measure, using an underwater viewing box.