How could the government try to pursude people to you less water?

For the most part, in the United States, US State water companies supply water to State towns & cities. In times of drought with water reservoirs low due a lack of rain and / or low snowfalls in the winter, the State will first place a ban on lawn watering. This measure alone would save millions of gallons of water. In a severe drought situation, TV commercials, flyers enclosed in water bills could emphasize

that using washing machines should be done with washing large loads of clothes rather than splitting the wash into small parcels.

Also, the State could have the water utility company put a surcharge on water usage above the highest amount used the previous year.

In large US Cities where the city owns & controls the water supply, a ban on the traditional opening of fire hydrants could be installed. This along with local TV & radio commercials emphasizing the need to preserve water can be aired.