The city's surface and ground water are essential to our social, economic, and cultural well being, as well as providing for recreational activities and are popular tourist destinations.

Water quality in our natural waterways is improved

Surface water quality is essential for supporting ecosystems, recreation, cultural values and the health of residents, particularly where drinking water supplies are reliant in whole or in part on surface water resources. 

Key points

  • The results of trend analysis between 2007 and 2015 show the majority of water quality parameters for all monitoring sites have remained steady over time.  This indicates that water quality is neither improving or declining. However, parameters at some sites have recorded an increasing or decreasing trend in concentrations.
  • In the 2015 year the Heathcote River catchment recorded the poorest water quality and the Otukaikino River catchment the best water quality.  This is consistent with the 2014 year.
  • The surface water monitoring indicates that the urban waterways are potentially contaminated from stormwater, wastewater and other inputs such as waterfowl faeces.  These may have short and long term adverse effects on aquatic plants, animals and fish, growth of aquatic weeds and/or algae and risks to people doing recreation.
  • The 11 sites in the Avon Heathcote Estuary/Ihutai sampled in the 2015 year, four have shown an improvement in water quality since the 2014 year, while one showed a decline in water quality. In the 2015 year just under half the sites had poor or very poor water quality and just over a third had good or very good water quality.  Sites closest to the sea tended to have better water quality than those closest to the rivers and streams discharging into the estuary.
  • Lake Ellesmere / Te Waihora and Lake Forsyth/ Te Roto o Wairewa have very poor water quality and are considered supertrophic (saturated in phosphorus and nitrogen). In recent years water quality appeared to be improving although in 2014, Lake Ellesmere / Te Waihora had a decrease in water quality.

Rivers in Christchurch

Avon River/Ōtākaro - Water Quality Trends (2007-2015)

Avon River/Ōtākaro - Water Quality Trends (2007 - 2015) graph

Source: Council, Surface Water Quality Monitoring


Heathcote River/Ōpāwaho - Water Quality Trends (2007-2015)

Heathcote River/Ōpāwaho  Water Quality Trends (2007 - 2015) graph

Source: Council, Surface Water Quality Monitoring


Styx River/Pūrākaunui - Water Quality Trends (2007-2015)

Styx River/Pūrākaunui - Water Quality Trends (2007 - 2015)

Source: Council, Surface Water Quality Monitoring


Halswell River/Huritini - Water Quality Trends (2007-2015)

Halswell River/Huritini Water Quality Trends (2007 - 2015)

Source: Council, Surface Water Quality Monitoring


Estuaries and Lakes

Avon Heathcote Estuary/Ihutai - Water Quality Index

Avon Heathcote Estuary/Ihutai - Water Quality Index graph

Source: ECAN, Water Quality Monitoring Reports


Lake Ellesmere / Te Waihora and Lake Forsyth /Te Roto o Wairewa - Trophic Level Index

Lake Ellesmere / Te Waihora and Lake Forsyth /Te Roto o Wairewa Trophic Level In

Source: Land Air Water Aoteraroa Website


More detail and information

 

Groundwater is safe from the effects of land use

Christchurch's drinking water is predominantly derived from groundwater sources in unconfined aquifers. Groundwater in unconfined aquifers is typically close to the surface, but the shallow water table makes it more vulnerable to pollutants, such as nutrients and bacteria from rural and urban land use. 

Key points

  • Groundwater quality is generally very good throughout Christchurch, with low concentrations of dissolved bacteria.
  • The best water quality occurs across the northern area thanks to seepage of clean water from the Waimakariri River into the aquifer. Groundwater quality in the south is still good, but the water contains more dissolved substances picked up during infiltration through the land surface.
  • The five wells that exceeded drinking-water criteria in the 2013 survey are affected either by known point sources of contamination or by natural anoxic (low dissolved oxygen) conditions caused by old swamp deposits near the coast and estuary.
  • One-off sampling for cadmium and boron found only one well near an old landfill where boron concentrations were above the drinking-water maximum accepted values.

More information can be found in the 2013 Christchurch Groundwater Quality Monitoring report produced by Environment Canterbury in November 2014.

More detail and information

Stream and river flows are maintained

Low flows impact on the water quality, ecosystem health and aesthetic values of the city's waterways.

There is a normal variation in the size and frequency of low flows from climatic factors which affect the amount and timing of rainfall. However, urbanisation can have a major effect on surface water flows, with increased impervious surfaces resulting in higher runoff and evaporation of water that would otherwise support base flows in the waterways. 

In the future, climate change may also impact on our waterways with Christchurch expected to be slightly drier in the future.

Key points

  • Due to many of the city's rivers being spring feed, the number of low flows is dependent on the amount of winter rain in each catchment and how this recharges the groundwater levels.
  • The number of low flow days in any of the rivers, as measured by the number of days with mean flows below the Mean Annual Low Flow (MALF), range each year from none to around half of the year in the case of the Halswell River.
  • Generally there is no trend in the number of low flow events in any of the rivers in Christchurch or Banks Peninsula. Individual catchments tend to behave differently as a result of external factors, such as the amount of rainfall.
  • The 2014 June year was significantly wetter than normal, whereas in February 2015 a drought was declared in Canterbury due to significantly less rainfall to recharge the groundwater levels.  This drought has continued into 2016. 
  • The 2015-16 drought appears to have had a more pronounced effect on flows in the Avon and Halswell Rivers with 229 and 185 days over the past 2 years with flows under the MALF respectively.  While other city rivers have had low flows they do not appear to be as sustained. 

Christchurch Rivers

Avon River/Ōtākaro - Number of Days with Low Flows

Avon River/Ōtākaro - Number of Days with Low Flows graph

Source: ECAN, River Flow Data


Heathcote River/Ōpāwaho - Number of Days with Low Flows

Heathcote River/Ōpāwaho - Number of Days with Low Flows graph

Source: ECAN, River Flow Data


Styx River/Pūrākaunui - Number of Days with Low Flows

Styx River/Pūrākaunui - Number of Days with Low Flows graph

Source: ECAN, River Flow Data


Halswell River/Huritini - Number of Days with Low Flows

Halswell River/Huritini - Number of Days with Low Flows graph

Source: ECAN, River Flow Data


Banks Peninsula Streams

Kaituna River - Number of Days with Low Flows

Kaituna River - Number of Days with Low Flows graph

Source: ECAN, River Flow Data


Alymer Stream (Akaroa Water Supply) - Number of Days with Low Flows

Alymer Stream (Akaroa Water Supply) - Number of Days with Low Flows graph

Source: ECAN, River Flow Data


More detail and information

Land Air Water Aotearoa : (LAWA) has current flow information for the above waterways, as well as information about abstraction consents and how water is used within the Christchurch - West Melton and Banks Peninsula surface water zones.

Environment Canterbury: Explanation on why Christchurch streams have low flows and have dried up in March 2016.  Also see their Drought Update July 2016.