It was not only is the river Jordan that John the baptised. We can also be baptized in other rivers because did not only baptised in river Jordan.
St. John 3:23 And John also was baptizing in Aenon near to Salim, because there was much water there: and they came, and were baptized.
I won't be logical to make it compulsory for people to be baptised in river Jordan alone because people from far country away from Israel may not have the money to travel to Israel to be baptized in river Jordan. Baptism is a step to salvation. Our Lord Jesus only about the manner baptism and not the place baptism. It therefore mean we are allowed to be baptized in other river.