Ōtūwharekai Ashburton Lakes Catchment Group – 8m deep fault line discovered from a magnitude 7-8 earthquake.

Kerry and Paul Harmer continue with riparian planting 560 carex secta plants within the Ashburton Lakes catchment on Sunday 22 March.

Gathering science/facts has been an ongoing focus for the Ōtūwharekai Ashburton Lakes Catchment Group, we then use these facts to drive catchment-wide and on-farm management decisions to minimise our farming footprint.

Our monthly water testing results of waterways travelling through our properties from several different sites show samples taken from the DoC estate (above where our stock graze), continue to show average nitrate tests of 0.2 ppmN. This result is above the targets Environment Canterbury (ECan) has set for the lakes (at 0.16 ppmN) and only a fraction of the national drinking water standards which are set at 11.3 ppm N.

How can the lake target be less than the water coming from ungrazed pasture from the DoC estate? This appears to be an aspirational target set in an office that has not been based on science and the water samples at source from the hills!

Paul Harmer of Castle Ridge Station standing in the test pit. The topsoil by his shoulder and rising to the soil surface clearly shows the 8m deep fault.

Riparian fencing and planting continue to be a focus on farms with a further 7800 plants going into these projects this autumn by the Ōtūwharekai Ashburton Lakes Catchment Group, spread over several properties.

Despite the scientific benefits of constructed wetlands, which show a reduction of sediment, nitrate and phosphate to further enhance water quality, we continue to be frustrated by ECans’ consenting policy.

The Catchment Group wants to construct a small wetland covering 2242m² (the size of 2.8 house sections in Ashburton) to test the effectiveness of a constructed wetland in the Ashburton lakes. This has been an ongoing project for almost two years.

 Whoever would have thought a trial to improve water quality, that is already purer than your drinking water bottle, would need five consents costing over $50,000.

There is a glimmer of hope with Governance and Senior management of ECan trying to help get the trial underway.

In other news from the area, there is currently an Otago University PhD student completing some investigations into a large earthquake fault line heading through the flats from the historic Hakatere homestead towards Lake Heron. Some test pits have been dug to expose material below ground. These test pits have shown evidence of a number of significant earthquakes and are some of the best-preserved examples in Canterbury and Otago.

The fault shows a very large ground shift, over 8m vertical shift, that occurred perhaps 1-3,000 years ago. Samples are being gathered from these test pits to determine the age of this fault.

The earthquake from the fault would have done more than rattle the windows or sway the lights, as the researchers think it could have been a magnitude 7-8 or more! More interesting facts being generated in our own little patch of paradise in Mid Canterbury.

Phill Everest is the Ōtūwharekai Ashburton Lakes Catchment Group facilitator.