I am a Summer Intern at HUD and a Full-time student at the University of Maryland. In our dorms at UMD, we have sensor toilets that detects how long you've been on the toilet. Although this may sound silly, the toilet accurately predicts what type of waste you are emitting (putting it kindly). The toilet then determines how much water is needed to flush away the waste. For bigger projects, more water is used. And for smaller projects, very little water is used. These sensors also have buttons on the top, in case you want to flush manually. You can determine how much water is needed to send your waste down the pipes.
This is an effective way to save money and cut down on the Government's water usage. With how many times a day people use the restroom (just to go #1) millions of gallons of water could be saved on a weekly basis.