1) Artificial 2) Emma and Dan are not natural 3) Like lake mead 4) Like Lake Mead or Lake Powell 5) Like Lake Nasser 6) Like lakes behind dams 7) Like reservoirs 8) Like some satellites 9) Not found in nature 10) Not natural 11) Produced artificially 12) Synthetic 13) Unnatural 
[adj] - (chemistry) not of natural origin
semisynthetic adjective not of natural origin; prepared or made artificially; `man-made fibers`; `synthetic leather`