River gauging

MNV undertakes river flow gauging and analysis to quantify flows in rivers and to generate statistics about the flow regimes.

We gauge all types of river systems as well as flows in ditches, channel and pipes and can carry out instantaneous flow measurements or continuous flow monitoring over long periods of time. The gauging results are used to quantify flood flows which will be used for flood protection designs, low flows to quantify minimum flows for habitat assessments or dilution of waste water. Continuous flow data is used to develop flow duration curves which are used for water resources assessments and the time series are used for hydrological modelling of catchments and the effects of land use change.

The equipment we use is supplied by SEBA Hydrometrie which is robust, accurate and versatile. We have a range of current meters for different applications including very small watercourses, larger rivers and rivers with heavy weed growth. For very deep rivers we use an Acoustic Doppler Current Profiler (ADCP), a sonar device which gives a profile of the speed of the water and the depth across the river. We follow international standards for taking the flow measurements and have rigorous quality control procedures to ensure the data are accurate.

The analysis we carry out includes the development of flow duration curves for the period of record and the scaling up of relatively short periods of data to long term flow duration curves using representative analogue stations from other catchments. From the long term data sets we carry out additional analysis to quantify the flow duration curve in average (P50), dry (P90) and wet (P10) years. We also undertake regional flow analyses to determine regional patterns in low, medium and high flows which makes the estimates of flow regimes in un-gauged catchments more accurate.