4.1 The science and practice of water flow measurement is known as (b) hydro-meteorology (d) hydrometry (a) hypsometry (c) fluvimetry 4.2 The following is not a direct stream flow determination technique: (a) Dilution method (c) Area-velocity method (b) Ultrasonic method (d) Slope-area method 4.5 In a triangular channel, the top width and depth of flow were 2.0 m and 0.9 m respectively. Velocity measurements on the centre line at 18 cm and 72 cm below water surface indicated velocities of 0.60 m/s and 0.40 m/s respectively. The discharge in the channel (in m/s) is (a) 0.90 (b) 1.80 (c) 0.45 (d) none of these. 4.6 In the moving-boat method of stream-flow measurement, the essential measurements 162 are (a) the velocity recorded by the current meter, the depths and the speed of the boat. (b) the velocity and direction of the current meter, the depths and the time interval between depth readings (c) the depth, time interval between readings, speed of the boat and velocity of the stream (d) the velocity and direction of the current meter and the speed of the boat. 48 The surface velocity at any vertical section of a stream is (a) not of any use in stream flow measurement (b) smaller than the mean velocity in that vertical (c) larger than the mean velocity in that vertical section (d) equal to the velocity in that vertical at 0.6 times the depth