Anniina Kittilä, ETH Zürich, Institute of Geophysics, Geothermische Energie u. Geofluide. Sonneggstrasse 5, 8092 Zürich, Switzerland e-mail: anniina.kittila(at)erdw.ethz.ch
Measurement of flow rates is import when trying to achieve sutainable closure of the mine site. In the closure planning stage eg. sizing of channels and ditches need to approximated properly to avoid spillages and excess cost. In post closure stage the environmetal loading of harmful substances need flow rate measurements that the load can be calculated.
In general, flow rates are measured in l/s if the discharge is small, but most commonly in m3/s. The places for monitoring, observation and measurements are chosen from those locations where the flow is stable and representable. This usually means that the direction of the flow must be same, and relatively stable, along the whole cross-sectional area of the channel. Considering technical success in measuring and obtaining representable data, the flow rate in the channel should not have strong and random fluctuations. Also, the cross-section of the channel should be clear and measurable. However, “snapshot” measurements can vary significantly over time, especially if the channel is very dynamic. Seasonal problems can also arise when the channel is choked with vegetation or ice (Mustonen 1986). There are various different methods, structures and devices to measure the flow rate both in open channels and in pipes, and some of the most known are presented in the following sections:
Mustonen, S. 1986. Sovellettu hydrologia. Vesiyhdistys r.y., Helsinki, 436 p. (In Finnish)