Water Solutions: Microeconomics

So we've all heard of the big-picture, let's-revolutionize-water "solutions" to world water shortages.  My personal favorite is probably ship-towing glaciers across oceans to consumers.  But sometimes we forget that the best solutions might not be revolutionary at all. 

That's why I'm proposing a simple microeconomic threshold-then-tax model for world water to deal with the problem that water is simply too cheap in wasteful nations:

• Make it illegal to not own a water-usage meter (just like with smoke alarms).
• In high per-capita consuming countries like the US, establish a threshold of acceptable water usage.  Let's say this threshold starts at 90% of the average American's usage.
• Below the threshold, keep the price of water low.
• Above the threshold, impose a tax that deters people (and corporations) from wasting water.
• Use the revenue from the taxes to fund source-solutions, such as grants to companies who invent water-efficiency technologies.

The best part about this policy is that the threshold eliminates any significant regressive qualities, so it would fix water usage but not fuel economic inequality.