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Surface water and the atmosphere
Published in Ian Acworth, Investigating Groundwater, 2019
The basic principle in the use of current meters is to measure the flux of water through a river cross-section by determining the velocity of the water at a large number of points in the cross-section. The most commonly used flow meters are the propeller type velocity meters. The current meter can be operated from a cable way, bridge or boat or by wading in the river if it is shallow enough.
Evaluating the impact of LID-BMPs on urban runoff reduction in an urban sub-catchment
Published in Urban Water Journal, 2023
Sedigheh Arvand, Zahra Ganji Noroozi, Mahdi Delghandi, Akbar Alipour
Since the rainfall volume transformed to runoff differs for each catchment, rainfall-runoff models need to be evaluated (Zakizadeh et al. 2022). For this purpose, it is necessary to measure runoff discharge (Q) in different rainfall events. In this study, runoff discharge was measured at the outlet of the urban drainage system (rectangular channel) during nine different rainfall events (Table 1). Due to the lack of hydrometric stations along the channel route, two methods of Float method and Current Meter were used to measure the flow velocity. The Current Meter can be hand-held in the flow in a small stream, suspended from a bridge across a larger stream. Based on the USGS standard, to determine the average velocity, the current meter must be mounted at a depth of 0.6. Once the depth of the flow exceeds 2 feet, the flow velocity is measured at depths of 0.2 and 0.8, and the average of these two velocities is assumed to be the average velocity in the vertical section (Chow, Maidment, and Larry 1988). After it began to rain, the depth of the runoff was measured at 30-min intervals in the drain leading to the outlet of the catchment (Figure 4). The drain was rectangular as shown in Figure 4, and the cross-section was calculated by measuring the depth of the runoff. At the same time, the runoff velocity was measured with the Current Meter and the Float method. The mean velocity was multiplied by the cross-sectional area to determine the runoff discharge at different times. The hydrograph of the urban runoff was determined by plotting discharge values versus time. These measurements were performed in the winter and spring of 2017.