Factors in selecting a gauging station site

A stream gauging station should be placed where the stage-discharge relation is stable and flow measurements are easy and accurate. Factors considered:

1. Straight reach: the channel should be straight and uniform for about 100 m upstream and downstream of the site, free from bends and sudden changes in cross-section.
2. Stable channel: the bed and banks should be stable (rock or hard material), with no scour, silting or shifting, so that the rating curve remains constant.
3. Control: a good natural control (rock bar, rapid or riffle) just downstream gives a sensitive and permanent stage-discharge relation. The site should not be affected by backwater from a confluence, dam, bridge or tide.
4. Flow conditions: velocity should be moderate, with no excessive turbulence, eddies, dead water or cross currents, and parallel flow lines.
5. Flood level: banks should be high and well defined, so that the gauge records the whole range of stages and flood discharge can be measured without overtopping.
6. Accessibility: the site should be reachable in all seasons for observers and equipment, near roads or villages, and with easy access to measure both low and high flows.
7. Location in the basin: near the point needed for the project, and not close to a tributary junction, so that the gauged flow represents the drainage area.
8. Suitable measuring section: a bridge, cableway or boat facility available for current meter work; gauge installation should be easy, and the cable/bridge should be safe.
9. Safety and security: protected from vandalism, floating debris, ice and erosion.
10. Permanency: the site should remain usable for long-term records, with no future development or change planned in the reach.