An irrigation system comprising a fluid-carrying conduit, two or more spaced-apart mobile towers, and a height-adjusting system. The two or more spaced-apart mobile towers are configured to support and move the conduit above a field. Each mobile tower includes a pair of legs, wheels, and a motor. Each leg has a first end coupled with the fluid-carrying conduit via a swivel connection and a second end. One of the wheels is connected to each of the second ends of the legs. The motor is for driving at least one of the wheels. The height-adjusting system is configured to move the second ends of the legs of each mobile tower relative to one another to raise or lower the irrigation system. The height-adjusting system may include an expansion mechanism for permitting adjustments to the height of the irrigation system or for applying a force to help make the adjustments.