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DATA REQUIREMENTS AND SPECIFICATIONS Upon completion of study area setup and documentation, collection of data for hydraulic simulation may proceed. It is assumed herein that the reader has some experience in the basic techniques required for the collection of data for hydraulic simulations. This discussion deals primarly with what to measure, not how to measure. A more complete amplification of basic measurement techniques may be found in the appendices. Several types of data are common to all hydraulic simulation tech- niques mentioned in this paper. Common data requirements include: 1. Stationing. 2. Headstake elevations. 3. Water surface elevations. 4. Bed elevations. 5. Discharge measurement. 6. Estimate of substrate size. If the Manning equation with velocity calibration or rating curve approaches are to be used, another type of data must be added to the list: j1_ 7. Velocity distribution at each transect. STATIONING Stationing refers to the measurement of the distances between transects. These measurements should be made between transects on both sides of the stream, particularly around bends. For consistency, cross sections should orginate from the same side of the stream. Identify left or right stream bank according to their position when looking downstream. Station indexing should start (0+00) at the most downstream cross section. A station index should be the distance along the thalweg (deepest portion of the channel) between transects, but may be given as the average of the distances measured on both banks. If the latter technique is used, make sure that-the headstakes for each transect are nearly equidistant from the banks. The precision for stationing should be to measure this. distance to the nearest foot (30 cm). HEADSTAKE ELEVATIONS Headstake elevations are usually referenced to an arbitrary datum at the benchmark (usually 100.00 feet). If desired, the headstake elevations may also be referenced to elevation above mean sea level if a reference of known elevation is near the study area. Headstake eleva- tions should be read to the nearest 0.01 foot if English units are used, or the nearest 0.5 cm if metric.. Headstake elevations should be surveyed from downstream to upstream, and then re-surveyed back to the ?0 2