Instead of using a representative sample to determine the size of a population, why not just count the individuals to determine the total number?

and after water is usually warmed by the sun the water temperature raises and then evaporates .

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.