A reliable lawn irrigation system keeps your grass lush and green throughout the heat of summer. If you don't have an underground system of "pop-up" sprinklers for your lawn, you may want to consider an above-ground approach -- otherwise you'll have to dig up the lawn to install the piping. Above-ground systems are also less expensive to install and you won't ever have to deal with finding a leaks in buried pipe.
Hose and Sprinkler
A sprinkler attached to the end of a hose is the simplest and most common above-ground irrigation system. However, watering your lawn evenly with this method is not so simple. The first step is to find sprinklers that fit the shape of the lawn. Rotary sprinklers are a good match for lawns with irregular, rounded edges, as they spray in circular patterns. Oscillating sprinklers are a better choice for rectangular shapes. You may have to experiment to refine your sprinkler setup so that all areas receive sufficient water without over-watering other parts of the lawn. Once you find the right combination of sprinklers, you may want to stake them in place and leave them all summer so you don't have to figure it out again each time you water.
Micro-sprinklers are perfect for small lawns. They can be added to existing drip-irrigation systems, an approach in which above-ground tubing is used to emit precise quantities of water exactly where the plants need it. The micro-sprinklers plug directly into the flexible tubing that supplies water to drip systems and can spray about 5 to 10 feet, depending on the model. You don't want to run the tubing through the lawn, so they are limited to the amount of lawn they can reach by spraying from the edges. If you run a line down both sides of the lawn, they could cover an area up to 10 or 15 feet in width, allowing for the overlapping spray pattern that is needed to ensure even coverage.
Spinklers on Risers
For larger lawns, you can use a bigger version of the micro-sprinklers. Rigid spray nozzles, similar to those used in pop-up sprinkler systems, can be mounted on short posts around the periphery of the lawn. Their spray distance is only limited by the amount of water pressure that can be supplied. Typically, a 3/4-inch flexible tube is used to supply these spray nozzles, which can be concealed with a covering of mulch. You will need barbed "T" fittings to connect each spray nozzle to the supply line.
Timers for hose-end sprinklers are reminiscent of a kitchen timer. You turn the dial to the time you want the water to stop and it turns it off for you -- saving lots of water for those who are prone to turn on a sprinkler and forget about it. Micro-sprinklers and their larger cousins can be controlled with a timer that turns them on and off according to a weekly regimen. Simple, battery-powered versions can be mounted right on the hose faucet, but fancier systems are mounted in the garage and are like a mini-computer, capable of complex watering schedules.