Simplify the following text for a Grade 10 native English-speaking person.
Original: In the 20th century , the development of major irrigation areas in the Murray and Murrumbidgee valleys has led to the introduction of crops such as rice and wine grapes .
Simplified: In the 20th century , the building of major irrigation areas in the Murray and Murrumbidgee valleys has led to the introduction of crops such as rice and grapes .