When sun shines on surface water the water evaporates to form clouds. Rain falling from those clouds travels through what is called the water cycle.
Outside Hoses and Faucets
Hoses and outside faucets are often left running. Common garden hoses (2" or 5/8" inch diameter at full flow) can use up to 630 - 1,020 gallons per hour; larger hoses use more. The amount of your water bill, may increase substantially due to extended outside water usage or water loss.
And, it's important to prevent someone from using your water without your permission. When leaving your home for an extended period, turn off your outside faucet from the inside valve to protect against water loss.
In The Garden
Use plants, both native and from around the world, that do not need extra summer watering. Leave established plants that are often adapted to low water conditions.
Mulch beds to keep in moisture and help prevent weeds. Add compost to your soil to improve its water holding capacity.
Porous paving materials such as brick or gravel help keep water in the garden.
Use drip irrigation to apply water slowly, reducing run-off and promote deep rooting. Automatic timing devices allow efficient watering.
Water in the cool parts of the day to cut down on evaporation. Don't overwater -- water only when the soil is dry.
Water trees and shrubs which have deep root systems longer and less frequently than shallow-rooted plants which require smaller amounts of water or more often.
Raise your lawnmower cutting height. Longer grass blades shade each other and cut down on evaporation.