Page - 333 - in Book of Full Papers - Symposium Hydro Engineering

2.3. LONGITUDINAL SECTION SURVEY OF RIVERS IN THE RESERVOIR AREA Two methods shall be used for the longitudinal section survey of rivers in the reservoir area: First, the polar coordinate method; Second, GPS RTK real- time dynamic positioning method. The GPS RTK real-time dynamic positioning is the major method to be adopted with the polar coordinate method as the supplementary means. All the waterpoints within the reservoir area shall be surveyed in addition to the important feature points on land for data collection at a space of 20m. The main technical requirements for the survey operation are as follows: (1) Survey Scale: 1:2000. (2) Survey Coverage: From the Manwan HPP dam site to the warning line of the Xiaowan HPP (from the dam site to LM73), including a main-stream river length of 58km and a branch river length of 3km. (3) Characteristic positions, such as cross sections, bridges, hydropower plants, tributary inlets, water gauges, and the flow gauging cable way of the hydrometrical station shall be provided with the measuring points and labeled with names. The measuring points shall be densified at the river sections with rapids, drops, river bends and branching based on the principle of controlling the longitudinal change of the river. (4) The measuring point shall be indicated where it is at a place with a characteristic topography or ground feature. For example, villages, bridges, tributaries (gullies) inlets (left and right banks), rapids, drops, river bends, beaches, and the hydropower plants. Also, the elevations of the characteristic places like the bridge decks and hydropower plants (plant floor, tail water) shall be indicated. 333