Catchments water story information sources

We've created infographics to give you a glimpse of some of our monitoring results in the main river catchment areas of Southland: the Waiau, Aparima, Oreti and Mataura river catchments.

What is a catchment?

A catchment is an area where water is collected by the natural landscape.

Imagine cupping your hands in a downpour of rain and collecting water in them. Your hands have become a catchment. The outside edge of a catchment is always the highest point. Gravity causes all rain and run-off in the catchment to run downhill where it naturally collects in creeks, rivers, lakes or oceans.

Rain falling outside the edge of one catchment is falling on a different catchment, and will flow into other creeks and rivers. Some water also seeps below ground where it is stored in the soil or in the space between rocks. This is called groundwater.

The Waiau river catchments refers to the area where the main river is the Waiau. We used this method to break Southland up into four main river catchments areas, including the Waiau, Aparima, Oreti, and Mataura catchments areas.

Together the catchments of the four rivers drain 1.85 million hectares or 62% of the Southland mainland. Approximately 47% of all of the water in Southland streams is groundwater from these aquifers. Eventually, the region's fresh water flows into 24 estuaries before entering Foveaux Strait and the Southern Ocean.  

In these posters we show you the results of our environmental monitoring, along with information about some of the other things that make up the water story for these river's catchments. You can look up each of these things below for an explanation of how they form part of the water story, and where we got this information from.

Water use % - Irrigation, stock industrial

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, then divided up across the main areas of river catchments.

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): 

Aparima: Town supply: 2,077,839; Irrigation: 5,438,125; Stock: 5,916,205; Industrial; 1,576,740; Other:0

Mataura: Town supply: 9,587,285; Irrigation: 24,562,811; Stock:8,178,277.73; Industrial: 20,333,745; Other: 2,958

Oreti: Town supply: 18173886.5; Irrigation: 19281168; Stock: 10542343.95; Industrial; 26192247; Other: 101338

Waiau: Town supply: 5,354,987; Irrigation: 1,960,519; Stock: 1228,637; Other: 40,500

Meridian Energy: 34,122,460,000

Health at marine shellfish sites

Shellfish can bio-accumulate 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.

This pass/fail information represents the state of water quality at shellfish gathering sites, and whether is 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 popular sites in the catchment areas (part or our State of the Environment monitoring). If a site fails, the levels of bacteria are too high for shellfish to be taken from the site and consumed.

Microbiological water quality guidelines for marine and freshwater recreational areas, 2003

Nitrogen in rivers

We used 5 year's worth of data from our monthly State of the Environment monitoring (2012-2016) to assess whether nitrogen levels in rivers passed or failed ANZECC (Australian and New Zealand Environment and Conservation Council) guidelines.

Read the full report here.

Phosphorus in rivers

We used 5 year's worth of data from our monthly State of the Environment monitoring (2012-2016) to assess whether phosphorus levels in rivers passed or failed ANZECC (Australian and New Zealand Environment and Conservation Council) guidelines.

Read the full report here.

Nitrogen in groundwater

We used 5 year's worth of data from our monthly State of the Environment monitoring (2012-2016) to assess whether nitrogen levels in groundwater passed or failed ANZECC (Australian and New Zealand Environment and Conservation Council) guidelines.

Read the full report here.

Swimmable rivers (E.coli)

Swimmability in rivers refers here to E.coli (bacteria) levels 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.

These traffic lights show the state of rivers based their Suitability for Recreation Grading or SFRG for 2018. We monitor E.coli levels in rivers for four months over summer each year, and to calculate the SFRG we combine this with the last 3-5 previous years of summer monitoring to place the site into a Microbial Assessment Category (MAC). This is then combined with a site inspection that identifies risk factor which might make the site susceptible to bacterial contamination, called a Sanitary Inspection Category (SIC). This is combined with the MAC to give us the SFRG. We have used the term "swimmable" here for consistency, but it has a slightly different meaning to the national use by the Ministry for the Environment.

Swimmable lakes (E.coli)

Swimmability in lakes refers here to E.coli (bacteria) levels 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.

These traffic lights show the state of lakes based their Suitability for Recreation Grading or SFRG for 2018. We monitor E.coli levels in lakes for four months over summer each year, and to calculate the SFRG we combine this with the last 3-5 previous years of summer monitoring to place the site into a Microbial Assessment Category (MAC). This is then combined with a site inspection that identifies risk factor which might make the site susceptible to bacterial contamination, called a Sanitary Inspection Category (SIC). This is combined with the MAC to give us the SFRG. We have used the term "swimmable" here for consistency, but it has a slightly different meaning to the national use by the Ministry for the Environment.

Swimmable beaches (enterococci)

Swimmability at beaches refers here to enterococci (bacteria) levels in which, if too high, can make swimmers sick. Enterococci can enter waterways in human and animal waste via farming run-off and septic tanks or sewage.

These traffic lights show the state of beaches based their Suitability for Recreation Grading or SFRG for 2018. We monitor enterococci levels at beaches for four months over summer each year, and to calculate the SFRG we combine this with the last 3-5 previous years of summer monitoring to place the site into a Microbial Assessment Category (MAC). This is then combined with a site inspection that identifies risk factor which might make the site susceptible to bacterial contamination, called a Sanitary Inspection Category (SIC). This is combined with the MAC to give us the SFRG. We have used the term “swimmable” here for consistency, but it has a slightly different meaning to the national use by the Ministry for the Environment.

Check out our swimming page for the latest summer results and tips on choosing the best swimming spots.

QEII covenanted land: QEII National Trust covenants protect the habitat of threatened animal and plant species. The protection remains in place forever, even if ownership of the land changes, and cannot be removed for any reason. Go to https://qeiinationaltrust.org.nz/ for more information.

Farming: Farming is classed as sheep and beef, dairy (including support), deer, horticulture and arable (crops).

Page reviewed: 03 Dec 2018 3:21pm