Show feeds the che according to calculations of john birkenbine of philadelphia the drainage area of the mississippi river rive r is one and one fourth millions of square miles including nearly all of the country from the Alleg hanles to the and from canada to the gulf of mexico in his communication to the engineers club mr birkenbine estimates that one inch of rain falling evenly over this area would equal gallons of water the ave average ra ge yearly fall la in the mississippi watershed averages average from twenty to forty three inches according locality to the river iver has an average flow of cubic feet per second |