Short and Catchy:
* Drop by Drop, Make a Difference.
* Save Water, Save the Planet.
* Water: Use it Wisely.
* Every Drop Counts.
* Turn it Off, Turn it On.
Informative:
* Conserve Water, Conserve Life.
* Water Scarcity Starts with Us.
* Drought-Proof Your Future, Save Water Today.
* Water is Precious, Don't Waste It.
* A Little Change Makes a Big Difference.
Humorous:
* Don't Be a Drip, Save Water!
* Water: It's Not Just for Plants.
* Water: Use it, Don't Abuse it.
* Short Showers, Long Life.
* Turn the Tap Off, Not Your Life Off!
Bonus:
* [Your City Name] Needs You: Save Water.
* [Your Company Name] Supports Water Conservation.
Remember to choose a slogan that is relevant to your target audience and the message you want to convey.