You should find a good local map of the watershed and find a site within 1.5 miles of where your stream begins. The second sampling site should be within 1 mile of the mouth of your stream. Our Research question deal with changes in the Water Quality Index from the beginning and end of a stream. A hypothesis is merely a tentative explanation proposed to account for the observed phenomena. You are speculating on how natural events will turn out, based on what you know.
Science is systematic in method because it seeks a system of prediction.
That prediction is the hypothesis. Any hypothesis selected or formulated must be testable. Experiments generally test hypotheses by testing the validity of the predictions or conclusions derived from them. The primary purpose of designing scientific experiments is to test the proposed hypotheses. It is important to know that hypotheses are never proven - they are either supported or not supported by the data from the experimental results.