Why do the benefits of canals and dams not reach everywhere?

On which river - the Platte River or the Colorado River - does the Hoover dam on the Arizona Nevada border form a large reservoir? What year did waterfalls come out by TLC? In what continent and country is the Gibson Desert? How old is edinbrugh castle? What are three symbiotic relationships in Lake Erie? What is the total load of a stream? Who was the first dog to climb mount everest? Who built the first cape may lighthouse? What does water symbolize in the story Crossing the Red Sea from the bible? How long does it take to go through the channel tunnel? How is the flow of stream affected by erosion and deposition? How humans modified the landforms? What is a Zone of rapid change in ocean temperature is called the? What was the fertile mouth of the delta river called? How do wetlands improve water quality in a river system? What animals are in zoos? What weapons were used on concentric castles? Is the great salt the only salt lake in the world? The largest sea or lake in Asia? Where on the roller coaster do you feel you go the fastest?