Water, Water everywhere (or nowhere)

[Jo Farrow]

“Depletion of groundwater, left unabated, threatens to undermine food security, basic water supplies and resilience to the climate crisis on a global scale”. UN WATER

#WorldWaterDay2022 focusing attention on the importance of water. This year's theme Groundwater, draws attention to the hidden water resource. 

https://www.netweather.tv/weather-forecasts/news/11357-world-water-day-2022---unseen-groundwater

[Roger J Smith]

And yet desalination, one obvious strategy, is not a big priority in many developed countries. In the southwestern U.S., a combination of dry climate trends and rapid population growth has made the Lake Mead reservoir (behind the Hoover Dam on the Colorado River) dangerously short of available water, the levels vary from 10 to 20 metres below design levels. It is the same story upstream in Lake Powell which was not designed for irrigation, the dam is for hydro-electric power generation and requires a steady outflow, so in the drier climate Lake Powell is also draining down, leaving a nasty "bathtub ring" -- we crossed it by car ferry in 2018 and the ramp starts about a quarter mile up a hill from where the ferry can now dock. The other primary purpose of the Lake Powell project was to provide recreational opportunities which still exist although as with the ferry example, a lot of the infra-structure is now almost disconnected from the present water levels (and the lower lake level encourages more algae and prevents dispersion of waste dumped by some boaters). Another problem with the project is that the water being discharged through the dam into the Grand Canyon segment of the river is "bottom water" in the lake which is a lot colder than the previous river flow, and this has destroyed fish habitats in the river below Glen Canyon dam. 

There are other reservoirs in the western U.S. that have either shrunk down to half their design size and area, or else have dried up entirely (at least in dry seasons). So there is more and more pressure on artesian water systems which are being depleted more rapidly than nature can sustain. 

You would think the state governments of CA, NV and AZ could pool their resources and divert water supply from Lake Mead or the downstream Colorado River (what's left of it, that never reaches the ocean nowadays) to desalination projects located near the same places that need the water most. But little has been done. As far as I know there is not much of a push on in western Australia either, another region that must need more water than it has available. Chile and Peru would be other places that could benefit. We would never run out of ocean water and in fact the more desalination projects are underway, the slower would be the eventual rise in ocean levels if Greenland and other arctic ice continues to melt faster (as I think is very likely). 

West Africa is certainly another region that could benefit, and nothing done there yet at all, but political tensions make co-operation difficult. 

I have been thinking about these large-scale water balance issues for some time, people tell me that even the largest array of desalination projects one might imagine would not keep pace with rising sea levels, so that being the case, I also wonder if there are any sustainable methods of diverting glacial meltwater from reaching the Atlantic (from Greenland and or eastern Canadian arctic, Svalbard) and going instead into supply where needed. So far I have not come up with any workable model for this. But in theory, the water draining off melting land ice is still some distance above sea level where it runs out from under the ice margins (which have always been some distance inland in most parts of Greenland and are now a bit further inland). In most cases, there is a steep-sided valley or fjord which receives a torrent of meltwater which takes a few miles to reach the ocean. If that water could be stored and diverted then it would go some place where it would be useful, and not into a rising ocean. Both parts of that seem difficult to solve (storage outside the ocean, transport). You could do it on a small scale with some sort of ocean tankers but the cost effectiveness of that (and potential carbon neutrality issues) would be hard to justify, especially as the best uses of the water would be a long way from Greenland. 

In the past there were also schemes discussed for capturing large ice masses breaking away from the Antarctic ice shelves and directing them towards water-short coastal areas of the Pacific. Those schemes have never been tested in real world situations as far as I know. But in very general terms, this seems like the biggest challenge of the mid to late 21st century, otherwise supply from global agriculture will start to lag further and further behind demand. We seem to have plenty of money for all sorts of other projects ranging from the frivolous to the dangerous, but no money for water. That has to change. 

Edited March 25, 2022 by Roger J Smith