Southland water story information sources
There are many things that play a part in making up Southland's water story. It might seem that it rains, the rivers fill up, the water runs out to sea, but there is much more to it than this. Our climate, temperature, storms, snow-melt, water abstractions and discharges, and different land uses all affect our water quality and quantity. This in turn affects the life in our waterways, our ability to take food from them, swim in them, and enjoy them as those before us have.
While we couldn't fit everything that affects our waterways on one infographic, they are a good way to introduce some monitoring information to spark your interest, and give you the opportunity to look deeper. You can look up each of these things below for an explanation of what they mean and how we got these numbers.
- Where we report on monitoring results from more than 20 sites, we have described the results as percentages.
- We have not included Fiordland and Stewart Islands as our information is limited, and water quality is typically good in these locations.
The ability to take water is allocated through consents from regional councils. Not all consented water is used. Managing water takes is important for maintaining flows downstream. If flows of rivers are reduced, algae and fine sediment can build up, which reduces amenity and recreational value and results in a poor habitat for aquatic species.
These percentages represent the allocation of water for use in Southland each year, divided across different uses.
The numbers do not include Meridian Energy's use for Manapouri's power station, as this is very large in comparison to other takes, (equating 40% of all the water used in New Zealand) and including it in the category of industry would have made the other water takes seem disproportionately small.
The numbers (in cubic metres per year):
- Town supply: 35,193,998
- Irrigation: 51,242,623
- Stock: 25,865,454
- Industrial: 51,921,804
- Other: 144,796
- Meridian Energy: 34,122,460,000
Estuaries are where freshwater from rivers and streams flows into and mixes with saltwater from the sea. They are home to native wildlife and often suffer from human activities such as run-off from agriculture and wastewater discharges.
The traffic light system for results shows an overall estimate of estuary health. We monitored the health of ten of Southland's 25 estuaries. We measured a range of health indicators like mud, algae growth, and the presence of nutrients like nitrogen and phosphorus. We used this information, along with the New Zealand Estuary Trophic Index to generate an estimate of each estuary's overall grade or Estuary Ecological Condition.
The health of two of the estuaries monitored is very good, two are good, two are fair, and four are poor. The New Zealand Estuary Trophic Index could not be used to generate an overall grade for the Waimatuku Estuary, however using our monitoring information we are able to grade is as 'Fair'. Click here for more on estuaries.
Health at marine shellfish sites
Shellfish can bioaccumulate or store up bacteria like E.coli and enterococci which has come from rivers or the ocean. This can make those who eat them sick.
The traffic light system for results represents the state of water quality at shellfish gathering sites, and whether it meets the Microbiological Water Quality Guidelines for Marine and Freshwater Areas (2003) set by the Ministry for the Environment. This is based on our 2017 monthly monitoring for harmful bacteria at 8 popular sites (part or our State of the Environment monitoring). If a site fails, the levels of bacteria in the water are too high for shellfish to be taken from the site and consumed.
While national guidelines are pass/fail, we use a traffic light system to demonstrate this. For more on water quality at our shellfish sites, click here.
Stream insects, worms and snails (macroinvertebrates)
Macroinvertebrates are spineless aquatic animals that include the iconic species caddisflies and mayflies, and play a vital role in stream ecosystems. They are used a measure of river and stream health as each has a relatively well-known sensitivity or tolerance to stream conditions.
This traffic light represents macroinvertebrate community state, or meaning the numbers present, and the diversity of species. The percentage shows the results of our annual summer monitoring of macroinvertebrates at 81 rivers and stream sites across Southland, between 2010 and 2017, which we assessed using the Macroinvertebrate Community Index grading guidelines.
The numbers: 15 sites are excellent, 30 are good, 30 are fair and 7 are poor.
Periphyton grows naturally in all water; however its growth is enhanced by high nutrient levels. Very thick mats of slime algae can be toxic to humans, can reduce the amount and type of food available for fish and remove oxygen from water.
The traffic light system for results represents periphyton state (using percentage). The percentage shows Summer algae monitoring at 33 sites across Southland has been compared to the compulsory national bottom lines (National Objectives Framework) for periphyton from the National Policy Statement for Freshwater Management. A model was also used to generate this information because the suggested three years of monthly observations of algae is not available. The colours represent the likelihood of problem algae being present for 2-3 months each year. The national bottom line is the boundary between yellow and red.
The numbers: 33 sites: 8 sites are very good, 8 are good, 9 are fair, and 8 are poor.
Nitrogen in rivers
While nitrogen is used as a fertiliser on land, when too much gets into rivers and streams it can cause aquatic weeds and algae to grow too fast. This increased plant growth can reduce oxygen in the water and threaten aquatic ecosystems. Nitrogen enters rivers through livestock waste and fertiliser, septic tanks, and through wastewater and stormwater system discharges.
The percentages outlined represent total nitrogen trend.
Environment Southland has reported on 17 years' worth of data (2000-2016) from our 34 river sites which had enough data to be analysed. Trends were calculated to determine if the levels of nitrogen were improving (decreasing concentration trend) or worsening (increasing concentration trend). A certain number of sites were indeterminate, meaning a trend direction could not be determined.
The numbers: 34 sites: 1 is improving, 11 are worsening, and 22 are indeterminate.
Nitrate toxicity refers to the level at which fish and other species struggle to grow and survive due to toxic concentrations of nitrate in waterways.
The percentages represent state. Nitrate Nitrogen results from 55 river sites (monitored over the 5-year period from 2012 to 2016 as part of our State of the Environment programme) were measured against toxicity concentration objectives (National Objectives Framework or NOF) in the National Policy Statement for Freshwater Management (2014). The colours represent the amount of negative impact on aquatic life, and the number of species affected. The national bottom line is the boundary between yellow and red.
The numbers: 55 sites: 29 are very good, 17 are good, 9 are fair, and none are poor.
Phosphorus in rivers
Phosphorus, combined with nitrogen, can lead to excessive algae growth. Livestock waste and fertiliser, eroded soil, septic tanks, and wastewater and stormwater systems are the main sources of phosphorus in rivers.
The percentages represent the trend for total phosphorus. Environment Southland reported on 17 years worth of data (2000-2016) from our 21 river sites which had enough data to be analysed. Trends were calculated to determine if the levels of phosphorus were improving (decreasing concentration trend) or worsening (increasing concentration trend). A certain number of sites were indeterminate, meaning a trend direction could not be determined.
The numbers: 21 sites: 9 are improving, none are worsening and 12 are indeterminate.
Nitrogen in groundwater
Nitrogen in the form of nitrate can make its way into groundwater and aquifers by sinking through the soil, or through rivers and streams. Aquifers in Southland are an important source of drinking and stock drinking water for many towns, and nitrate contamination can affect people and animals, as well as the wider environment.
The percentages represent the trend for total nitrogen in groundwater. Environment Southland reported on 17 years worth of data (2000-2016) from our 23 groundwater sampling bores which had enough data to be analysed. Trends were calculated to determine if the levels of nitrogen were improving (decreasing concentration trend) or worsening (increasing concentration trend). A certain number of sites were indeterminate, meaning a trend direction could not be determined.
The numbers: 23 sites: 3 are improving, 15 are worsening and 5 are indeterminate.
Swimmable rivers (E.coli)
Swimmability in rivers refers to the E.coli levels in a river which, if too high, can make swimmers sick. E.coli can enter waterways in human and animal waste via farming run-off and septic tanks or sewage.
The percentage represents the number of monitored river swimming sites that meet the NZ Ministry for the Environment's swimming grade of "excellent". This is based on a combination of our data from monitoring sites, and MFE's predictive models. The colours blue, green and yellow are the number of sites where the E.coli levels are acceptable for swimming more than 20% of the year round; green is good and yellow is fair. Orange means intermittent, and red means unacceptable for swimming.
Swimmable rivers (Toxic algae)
Swimmability in lakes refers here to the threshold for toxic algal blooms, or cyanobacteria, which can make swimmers sick. Toxic algae is particularly likely to occur during warmer weather.
The percentage represents the number of monitored lake swimming sites that meet the NZ Ministry for the Environment's swimming grade of excellent. This is based on a combination of our data from monitoring sites, and MFE's predictive models. The colours blue, green and yellow are the number of sites where toxic algae is below the acceptable threshold for swimming more than 20% of the year round; green is good and yellow is fair. Orange means intermittent, and red means unacceptable for swimming.
In addition, we have created catchment specific infographics to provide you with our monitoring results for each of our main river catchments. Check out the information sources to the Waiau, Aparima, Oreti, Mataura infographics.
Some helpful definitions
Rūnanga: Rūnanga are the governing council or administrative group of a Māori Hapū or Iwi. Each Runanga contributes to water quality or Te Mana o Te Wai.
Landcare and catchment groups: Landcare and catchment groups coordinate restoration projects for wetlands, and riparian planting to protect waterways, as well as spreading good land management practices to improve water quality.
Consented discharges to water - wastewater and stormwater: Stormwater and wastewater discharge to water is managed through consents from regional councils. Managing discharges is important as this affects water quality downstream.
Stopbanks: Stopbanks along rivers have been built alongside rivers to protect the communities of Southland from floods.