Why was it important to always have a canal or waterway next to a field in Mesopotamia?

Colorado River width at Blythe CA? How many rivers are there in Europe? What is the closest building to mount everest? How does the new colossus affect the way we view the statue of liberty? Why does people brush their teeth in the river ganges? Where is situated 'toor' mountain? What are 5 African countries that touch the Mediterranean sea? How many times could mt Everest fit into Hawaii? What restrictions are placed on national historic homes? What is the famous bridge in Dublin? Direction of heat flow? What was indus river known as in ancient times? What is San Juan Bautista known for mission? What rock is used in red fort? Are the Rocky Mountains located in New Mexico? What is the continental slope of the pacific ocean? What supernatural features does the lake have in Beowulf? How do ecologists generally divide the oceans into zones? Animals in Victoria falls? Why was Stonehenge built in wiltshire?