If you find that water is running off your lawn when you water, then you will need to adapt your watering strategy. A simple cause of run off could be that you are adding more water to lawn than the soil can absorb - if this is the case slow the rate at which you water. This can be a common problem when using sprinkler systems.
Aerating your lawn will also help – because by forking your lawn and adding small holes, it will allow water to penetrate deeper into the soil and allow fresh oxygen to reach the grass roots which is required for healthy grass growth.
A good alternative to this is the use of water butts which collect water when it rains. This water can then be used on flowers, plants or on your garden when water is in short supply.
Another helpful tip is to cut your grass frequently and leave your grass clippings on the lawn. As the grass clippings break down and return to the lawn, they release water and nitrogen which is absorbed by the soil, helping to promote healthy grass growth.