Clean Green Tasman?
Remember how the Tasman District Council lost their fight to keep its secret contaminated site register under wraps?
It turns out that our record of preserving the integrity of our water is not a battle we are winning either. The latest groundwater nitrate report shows little improvement and paints a bleak picture moving ahead.
The following excerpt is from the introduction of said 2005 WAIMEA PLAINS GROUNDWATER NITRATE SURVEY – REPORT EP05/11/11:
Over 90 groundwater samples were collected from the Waimea Plains aquifers between 19 May and 4 August 2005 and tested for nitrate. Well owners have been informed of their results. This survey was the fourth such plains wide survey of groundwater nitrate concentrations. Previous surveys were undertaken in 1986, 1994, and 1999/2000. . .
The most striking aspect to the data is the presence and persistence of areas of high nitrate concentration in the groundwater. Of all the bores sampled in the 2005 survey, 36% were above (i.e. did not comply with) the NZ drinking water standard of 11.3 g/m3-N.
Groundwater from the Waimea Plains is widely used. By volume irrigation is the predominant use, however, many households rely on groundwater for drinking water supplies, and a significant portion of the Richmond Municipal Water Supply is sourced from a bore field adjacent to Lower Queen Street.
The elevated nitrate concentrations encountered in the groundwaters of the Waimea Plains do not meet the groundwater quality required by Policies 33.1.3 and 33.1.4 and Schedule 36.1B of the TRMP. These policies require that the groundwater and land resources of the Waimea Plains are managed so that the groundwater is not contaminated so as to make it unpalatable or unsuitable for consumption by humans after treatment (equivalent to coagulation, filtration and disinfection). Nitrate contamination of water can not be readily treated by coagulation, filtration or disinfection. [emphasis mine]
If this is not concerning to those of you living in the affected drinking water area, it should also concern those who like eating fish, whitebait, and shellfish caught in or in the vicinity of the area. There are no practical treatment options for the removal of nitrate from groundwater.
Especially concerning, in case you missed it in the introduction, is the statement found in the summary: “There are no practical treatment options for the removal of nitrate from groundwater.”
In other words, this is not a problem that will go away unless we prevent it from occurring in the first place. It is especially pertinent as the problem crops up in another study.
The potential effects of the Lee dam on water quality are considered minor or able to be mitigated by providing flushing flows (up to three flushing flows over 5 m3/sec for >3 hours from November-April inclusive aimed at interrupting any periods of low flow >40 days) and good practice during dam construction (Young and Doehring, 2014). However, providing fish passage over the dam for red fin bully and longfin eel (downstream only with hydro-electric generation) will be challenging, and some off-set mitigation is recommended. There are potential indirect effects of the dam as more water available for irrigation could increase nitrogen leaching to groundwater, particularly on Ranzau soils where leaching rates are highest. Modelling (using SPASMO) has shown that, compared with nitrogen losses from current land uses, full irrigation within the Lee Dam service zone could increase nitrogen concentrations entering the groundwater by 23% and in a hypothetical worst case by up to 50% if the entire plains were converted to irrigated market gardening (Fenemor, 2013). These increases, however, are mitigated (diluted) by increased drainage rates to groundwater of 6% and 19% respectively caused by the increased irrigation. The effect of this on surface water would be most prominent in spring-fed streams in the lower Waimea Plains, particularly Neimann Creek.
2015 State of the Environment Water Quality Report information for the Waimea Water Management Area.
The dam itself may not be bad, but this study suggests that it will magnify our water nitrate issues (already failing the human consumption recommendations). I am not advocating that this means we should not build a dam, but I am advocating that we need to take the water nitrate issue seriously.
If we do not figure out a way of better managing nitrate levels before a dam is constructed then our clean and green image is going to be seriously tarnished by big hazard signs on waterways warning people not to drink the water. Remember we have no feasible method of treating nitrate infused water.
How seriously do you think the council should be taking this issue?
Do you think that no improvement between reports stretching back to at least 1986 reflects a council taking the issue serious enough?