Though methods, techniques, and instrumentation vary, all gaging efforts involve the determination of
- channel shape
- cross-sectional area of the channel
- channel “roughness”
- water depth
- water volume
Once a gaging location has been selected, a reconnaissance of the site determines site-specific gradient, channel configuration, morphology, confluences with other water bodies, and the location of natural and manmade structures that might affect discharge and gaging. Most gaging instrumentation is permanently mounted to a structure for extended periods of time. Therefore, the equipment and instruments used must be rugged for long term deployments and capable of functioning reliably and accurately under any extreme conditions. Some maintenance is always necessary, but can be reduced significantly with careful selection of the most appropriate gaging, logging and communication equipment and instruments.