Simplify the following text for a Grade 13 native English-speaking person.
Original: The delineation of the Riverina region by government agencies and other bodies varies , but in common usage it generally comprises the agricultural and pastoral areas of New South Wales , west of the Great Dividing Range and in the drainage basin of the snow-fed Murray and Murrumbidgee Rivers .
Simplified: The area of the Riverina region is not fixed , but it usually includes the farming and pastoral areas of New South Wales , west of the Great Dividing Range and in the drainage basin of the snow-fed Murray and Murrumbidgee Rivers .