Aquifers – the water source humans tend to forget until it is too late
Before I read Maude Barlow and Tony Clarke’s ‘Blue Gold’, I didn’t know anything about aquifers. In fact, I didn’t know how to spell the word! So it was a total shock to learn that the largest aquifer in the United States, The Ogallala Aquifer in Texas, was in danger of drying up. In the scientific language of aquifers, it was being drained faster than it could recharge. Many areas of the world do not get enough rainfall to be able to draw water from rivers or roof tanks because they are arid or semi-arid.
So, what is an aquifer? These are layers of underground material that hold water, and are made up of porous rock or sediments like sand and gravel. Some of the rain that falls will be soaked deep into the ground and accumulate in these underground stores. Some of the water in the planet’s aquifers are centuries old, with humans having dug access to this source of water for centuries, either as wells or deep boreholes.
However, something terrible is happening to this crucial water source. Last year, a research paper outlined data that suggested that of the 1,700 worldwide aquifer systems, groundwater stores have declined by 71%. More than 2/3 of these aquifers are declining by 0.1 metres a year and, even worse, 12% are declining at 0.5 metres a year. Nearly a third of aquifers are experiencing accelerated depletion and this is just going to get worse in places where climate change is experienced as more excessive droughts.
Not being able to ‘draw water’ if it is needed is bad enough, but the drying aquifers can also trigger peculiar geological and hydro-logical side effects e.g. the shrinking of rivers and groundwater loss along coastlines allows seawater to flow subterraneously back into the depleted aquifer, increasing the salinity in the remaining groundwater. The land can also sink and it is estimated that in the next two decades, this subsidence could affect 1.6 billion people. In California, the overuse of groundwater for agriculture has already caused the land to sink dozens of feet in some places. You might read this and think we don’t have a problem on Waiheke as most houses have alternative water sources i.e. water tanks. I thought this until I read a Gulf News letter from a hydrologist some years ago when Waitemata Infrastructure Limited (WIL) wanted to build a huge retail and apartment complex at Matiatia. Planned bore use was going to draw a very large amount of water per year. The hydrologist pointed out the potential risk of excessive withdrawal of groundwater, so close to the coast, which can lead to saline pollution of the remaining groundwater. WIL’s application failed, but since then I have noted that more and more resource consents for bores (domestic and commercial) are being applied for.
My questions to Council have led to the reassurance that recharge rates for Waiheke’s aquifer (under the island and over towards Coromandel) are checked regularly and are within sustainable limits. The current WaterCare 30-year water and wastewater plan also repeats these reassurances. However, I’m not sure how much increasing severe climate change events have been factored into these calculations. We may of course have excessive wet periods, which could help recharge the aquifers naturally, but we may have more excessive dry periods, where people rely more on their bores, rather than their water tanks. The mainland based planners in Council imagine an accelerating population growth rate for Waiheke, restricted only by how much land capacity there is for building. At no point is anybody asking the question of ‘do population numbers need to be aligned with water source capacity and therefore capped?’ The capitalist growth narrative is still dominant in national and city economic thinking and, therefore, exorbitantly expensive solutions for Waiheke residents and ratepayers like island wide reticulation (where water is piped to the island) may be foisted on us.
No one on Waiheke or few people in other parts of the country are planning for, or even talking about sustainable ‘aquifer recharge’ solutions e.g. finding aquifers to direct storm-water into or deploying urban infrastructure that soaks up rainwater (sponge cities). We have a small scheme for recycling wastewater via the Owhanake system but as most of our wastewater is dealt with sustainably onsite and eventually trucked away for processing, recycling and replenishing land; we don’t need ‘supercity’ solutions.
We do, however, need to keep up our well-documented annual water usage lower compared to the isthmus and keep asking hard questions about our aquifer health though – of those testing its recharge rate, plus questioning the need for unlimited population growth on a finite island with no notable waterways.
Sue Fitchett
Project Participant