Data interpretation is difficult under the simplest of conditions and requires hydrologic studies that are carefully designed. Good research presupposes carefully collected data, as well as data that were obtained at times when the information content was highest. To accomplish the careful design of hydrologic studies and to obtain quality data, the U.S. Geological Survey works through small organizational units. The principles of a well-designed study are: 1) Use the scientific method, 2) define the problem and the approach, 3) state the objectives of the data collection, 4) determine what and how to sample, 5) decide where to sample, 6) begin report preparation early in the study, 7) do the work with little or no rework, and 8) complete the report on schedule.