Whanganui Enviro - Kaitiaki

Rotokawau / Virginia lake This headline, taken from the  Whanganui Chronicle a few years ago, should serve to remind us that we are now entering the algal bloom season in Rotokawau / Virginia lake, Whanganui.  Algal blooms are one of the major effects of a natural lake process called  eutrophication  and they appear to occur in Rotokawau / Virginia lake any time from spring through to late autumn .   Eutrophication is caused by a build up of excessive amounts of nutrients in lake water and this leads to a proliferation of algal blooms that are sometimes toxic, but which eventually die and decay leaving a lake depleted in oxygen and unable to support much life.  Although eutrophication occurs naturally, it is exacerbated by human activity such as increased nutrient flows that result from surrounding fertiliser use and sewage discharge, and from  animal excrement and the removal of natural plant buffer zones around the lake edge.  Nitrogen (N), needed to build proteins and phospho

First collect your water sample Google maps Rotokawau / Virginia lake was accessed on its southern end adjacent to the Great North Road.  Here it was possible to submerge a stoppered one litre glass bottle 300mm below the surface in water at least one metre deep in accordance with sampling protocols. This was far enough away from the duck feeding areas for sampling not to be directly impeded by faecal contamination.  We started testing on 20th September, 2018 and this has been repeated on a weekly basis at roughly the same time of the day, ever since.  It is our stated aim to monitor Rotokawau / Virginia lake for a whole year. The water samples are tested on site and back in the school laboratory.  A Vernier Logger Pro data logger is used as an interface to run an assortment of ion selective electrodes and probes and we also have a Thermofisher pH probe and conductivity meter.  The full set of measurements made each week at Rotokawau / Virginia lake is as foll

Rotokawau / Virginia lake, May 2018 https://www.nzherald.co.nz The health of Rotokawau / Virginia lake has been in the local news quite a lot over the last few years because of the frequency with which unsightly algal blooms plague the lake. Our interest as a school Science department developed out of a place-based study we were doing at the time, researching and writing about the impact of farming on the environment. It did not take long for students who were learning about eutrophication and the effects of fertilisers and farm run off on the quality of water in our waterways, to ask the question why was Rotokawau / Virginia lake affected in the same way? After some thought and considerable investment, we decided we would undertake to monitor the lake over the course of one year to see what we could find out. The Māori name for Virginia lake is Rotokawau and it was given this name after the black shag birds that use to inhabit the lake area in large numbers. Pākehā ca

The trees and shrubs three months after the experiment (From left) 4. Wharangi, 1. Kohekohe, 3. Five finger, 2. Kokomuka There was no discernible difference in the growth rates of the trees and shrubs under any of the watering conditions  used in the experiment except for Kohekohe whose growth rate remained static for all water types.  This probably says more about the Kohekohe specimens used or the unsuitability of the growing conditions rather  than the effect of the watering.  

1. Dysoxylum spectabile (Kohekohe) maoridictionary.co.nz Four native NZ tree and shrub species were supplied by PTC for us to gauge their tolerance to grey water and suitability for use in a wetland area. 1. Dysoxylum spectabile (Kohekohe) 2. Hebe elliptica var crassifolia (Kokomuka) 3. Peseudopanax arboreus (Five finger) 4. Melicope ternata (Wharangi) 2. Hebe elliptica var crassifolia (Kokomuka) nzpcn.org.nz The native plants were over-wintered in the school horticulture area until spring and then nine individual plants of each species were split into three equal groups and treated with 2 litres of collected  tap water, grey shower water and eco-friendly grey shower water on a weekly basis.  This enables the scientist to check out how individual species cope with the different types of grey water against a tap water control experiment. 3. Peseudopanax arboreus (Five finger) nzplants.auckland.ac The height and maximum width of each individual pl

One of the suggestions put to us at the start of the project was to build a wetland area to process grey water generated within our school.  This would require us first of all, to develop an understanding of the science behind grey water processing and then build a pilot-scale system on school grounds.  Whanganui District Council have given us permission to build a small system outdoors because our environmental impact would be small  and then our research on natural systems moved us towards adopting a water tolerant plant and  soil filtration system as our preferred method of processing.  Our inspiration can be found at    https://www.milkwood.net/2012/10/16/building-a-simple-biological-diy-greywater-system/   Grey water is very variable in composition.  It can contain soap and detergents and bits of dead skin, hair and lint that get washed off our bodies when we shower.  It should be low in nitrogen compounds as human urea is flushed separately down the toilet. 

Partnership Through Collaboration (PTC Trust) organised for our students to visit the Institute of Environmental Science and Research (ESR) Laboratory in Porirua. Along with the Year 10 STEM team, we also took with us students from the Y12 Horticulture class whose job it will be to create a landscape design when we install a pilot grey water system in the school grounds. The day long visit included a visit to a retired couple's home on the Kapiti coast to see first hand how waste water can be recycled. The trip was extremely useful for us as Science teachers because it enabled us to talk to experts in the field and to firm up the plans we had for this project. You will hear about our progress soon enough but we got some great ideas from the day to help get our project underway.