Question: Richardson has to pay for a minimum amount of water whether it's used or not. Where is the incentive to conserve? Isn't this like the stupidest thing you ever heard of?
Answer: Think of it this way: Richardson isn't paying for the water as much as for the infrastructure needed to supply that water -- reservoirs, pipes, pumps, water treatment facilities, etc. Those things cost the same amount of money in wet years as in dry years. You wouldn't tell Ford Motor Company, "I know I bought an F-150, but it turns out I'm not hauling as much as I thought I would. Can I get a break on my truck payment in months I don't haul as much?" Likewise, you shouldn't tell the North Texas Municipal Water District (NTMWD), "You know that reservoir you built for me? Turns out I probably don't need one that big this year. Can I just not pay for it this year?"
How much infrastructure is built is based on how much water we used in the past. Each year, growing cities set new high water marks (pun intended ;-). Mature cities with good conservation programs like Richardson don't. Richardson gets a bit of a refund for water it's contracted for but doesn't use, but it still has to pay something, year after year, for water not used.
Because more cities are staying under their own high water mark year after year, wet years and dry (Richardson's was in 2001), the NTMWD recognizes the need to rethink its contracts with member cities. It's agreed to establish a forum to address concerns about the current methodology that determines how much each city pays for water. So relief might be on the way.
In the meantime, keep conserving, even in wet years. It establishes habits that help ensure that the water will always be there when you turn on the tap. Paying for that comforting assurance is a first world problem.