Having not done any particularly rigorous research, the evidence I have seen indicates that agriculture is the primary driver of natural freshwater store depletion. Climate change may be an exacerbating force, but it is highly likely that freshwater stores are being consumed significantly faster than they are being naturally replenished even if we assume no changes in the natural water cycle. Here is a graphic illustration of the depletion of the Aral Sea [1] and a link to Google Maps [2] to provide perspective on its size if you are unfamiliar with the geography.

In terms of solutions, as I have mentioned desalination is a functional solution that developed countries will likely be able to deploy that should make the worst case scenario of mass starvation or thirst unlikely. In fact, given the costs of desalination it is likely that developed countries will be able to deploy it just because they do not want any lifestyle changes. Other than that, the most likely solution will be a massive reduction in water usage which is, based on my recollection, predominantly agriculture (~70%) followed by industrial (~15%) followed by recreational/aesthetic (~12%) followed by personal (~3%) or something similar to that distribution. Given how small personal usage for things such as drinking, cleaning, bathing is, this reduction would largely need to come from agriculture with maybe some coming from reductions in industrial and aesthetic uses such as lawns. Frankly any calls to reduce personal usage should probably be seen as evidence of a lack of understanding of the problem or possibly even a deliberate act of sabotage since it would have little impact on the problem, but come with a large human cost.

In terms of the feasibility of water usage reduction, a large reduction in water usage seems quite doable in the US given that it consumes ~3-4x more per-capita than similarly wealthy European countries. To some extent this is a partial misrepresentation since the US is a major food, and thus water, exporter, but I am fairly certain even without looking at the underlying numbers that the US can significantly reduce consumption without significant lifestyle changes. From what I have heard, but not investigated thoroughly, this is mostly blamed on the relatively large amount of meat consumption/production in the US which is not implausible on its face. Assuming this is the case, a reduction in meat consumption to European levels would be a fairly minor change in lifestyle that would dramatically reduce water consumption. Alternatively, the development of meat substitutes or artificial meat with far lower water needs could solve that problem. I am uncertain if this is a sufficient reduction as I do not know about the raw consumption/replenishment rate of water resources, but if it is not it would at least provide a significantly longer lead time to solve the problem in other ways.

In terms of research into desalination or the like I do not have any particular resources. Most of my knowledge is fairly surface level from piecing together random snippets that I find and doing some first-principles analysis.

[1] https://earthobservatory.nasa.gov/world-of-change/aral_sea.p...

[2] https://www.google.com/maps/place/Aral+Sea/@45.9900368,43.86...