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Describe how irrigation ditches are laid out.

The mother ditch, or main ditch or canal, leads water to the headgates, which control the main flow. Lateral ditches run perpendicular to the main ditch and bring water to the fields for field irrigation. A drain canal brings water back to the stream.

Explanation:

disease was the number one killer of native peoples. they had had little exposure to the diseases of europe. this led to some villages being almost completely wiped out and some tribes destroyed.

i believe it was spain