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Audio, Radio New Zealand

For many years the Heathcote-Avon estuary was the dumping ground for Christchurch's sewage. Then, in 2010, the wastewater was diverted well out to sea, via a long pipe. David Schiel from the University of Canterbury and John Zeldis from NIWA were investigating the effects of this diversion on the health of estuary when the 2011 Christchurch earthquakes happened, re-engineering both the estuary and their experiments.

Research papers, University of Canterbury Library

The Avon and Heathcote Rivers, located in the city of Christchurch, New Zealand, are lowland spring-fed rivers linked with the Christchurch Groundwater System. At present, the flow paths and recharge sources to the Christchurch Groundwater System are not fully understood. Study of both the Avon and Heathcote Rivers can provide greater insight into this system. In addition, during the period 2010-2012, Christchurch has experienced large amounts of seismic activity, including a devastating Mw 6.2 aftershock on February 22nd, 2011, which caused widespread damage and loss of life. Associated with these earthquakes was the release of large amounts of water through liquefaction and temporary springs throughout the city. This provided a unique opportunity to study groundwater surface water interactions following a large scale seismic event. Presented herein is the first major geochemical study on the Avon and Heathcote Rivers and the hydrological impact of the February 22, 2011 Christchurch Earthquake. The Avon, Heathcote, and Waimakariri Rivers were sampled in quarterly periods starting in July 2011 and analyzed for stable Isotopes δ¹⁸O, δD, and δ¹³C and major anion composition. In addition, post -earthquake samples were collected over the days immediately following the February 22, 2011 earthquake and analyzed for stable isotopes δ¹⁸O and δD and major anion composition. A variety of analytical methods were used identify the source of the waters in the Avon-Heathcote System and evaluate the effectiveness of stable isotopes as geochemical tracers in the Christchurch Groundwater System. The results of this thesis found that the waters from the Avon and Heathcote Rivers are geochemically the same, originating from groundwater, and exhibit a strong tidal influence within 5km of the Avon-Heathcote Estuary. The surface waters released following the February 22nd, 2011 earthquake were indistinguishable from quarterly samples taken from the Avon and Heathcote Rivers when comparing stable isotopic composition. The anion data suggests the waters released following the February 22nd, 2011 Christchurch Earthquake were sourced primarily from shallow groundwater, and also suggests a presence of urban sewage at some sites. Attempts to estimate recharge sources for the Avon-Heathcote Rivers using published models for the Christchurch Groundwater System yielded results that were not consistent between models. In evaluating the use of geochemical constituents as tracers in the Christchurch Groundwater System, no one isotope could provide a clear resolution, but when used in conjunction, δ¹⁸O, δ¹³C, and DIC, seem to be the most effective tracers. Sample sizes for δ¹³C were too small for a robust evaluation. Variability on the Waimakariri River appears to be greater than previously estimated, which could have significant impacts on geochemical models for the Christchurch Groundwater System. This research demonstrates the value of using multiple geochemical constituents to enrich our understanding of the groundwater surfaces-water interactions and the Christchurch Groundwater System as a whole.

Images, eqnz.chch.2010

With the land dropping about 1metre to 1.4metres after the earthquakes, a few roads besides the Avon and Heathcote Rivers are flooded with very high tides. Extra stop banks (on right) erected after the quakes have helped, but the road is now well below high water level. New Brighton Road, just short of New Brighton. The Pages Road bridge may b...

Audio, Radio New Zealand

A 22-year-old self-employed dairy farmer hopes his success through winning a new Maori farming award will inspire other young troubled Maori to follow their dreams; The Chairperson of Nelson's first Maori language immersion school says there's been a shift in attitude among members of the public - who now understand the school won't be exclusive; The former National MP Sandra Goudie is calling for Waikato ratepayers to oppose two Maori seats that the Regional Council is introducing at next year's election; Liquefaction from the Christchurch earthquakes may have unearthed four taonga on the banks of the Heathcote river.

Audio, Radio New Zealand

The former National MP Sandra Goudie is calling for Waikato ratepayers to oppose two Maori seats that the Regional Council is introducing at next year's election; The Chairperson of Nelson's first Maori language immersion school says there's been a shift in attitude among members of the public - who now understand the school won't be exclusive; A 22-year-old self-employed dairy farmer hopes his success through winning a new Maori farming award will inspire other young troubled Maori to follow their dreams; Liquefaction from the Christchurch earthquakes may have unearthed four taonga on the banks of the Heathcote river.