premise: Salt River Valley is in central Arizona, surrounding Phoenix.
hypothesis: Gila River Valley . The central portion of the river flows on the southern Phoenix valley region - ( where Phoenix , in the Salt River Valley joins the Gila River Valley ) , and the final sections in southwestern Arizona form agricultural , irrigated smaller valleys within the Gila River valley , ( for example Dome Valley , Mohawk Valley , and Hyder Valley ) . The Salt River Valley is an extensive valley on the Salt River in central Arizona , which contains the Phoenix Metropolitan Area .