Test: Streamflow Measurement - 1 - Civil Engineering (CE) MCQ

Indirect methods are those methods which make use of relationship between the flow discharger and the depths at specified locations. Two types of these indirect method are flow measuring structures and slope area methods.

The float-operated stage recorder is the most common type of automatic stage recorder in use. In this a float operating in a silting well is balanced by means of a counterweight over the pulley of a recorder, To protect the float from debris and to reduce the water surface wave effects on the recording, silting wells are provided in all float- type stage recorder installations.

Discharge in the channel
= x area of channel Area of channel

Area of channel

The moving-boat technique measures the velocity over the width of a segment by suspending the current meter at a constant depth during the transverse of the boat across the stream.
The measured velocity and the additional information of the depth gives the discharge.
Thus, velocity of the river is determined by whether the current meter measures along or opposite of the stream and the velocity it measures.
The depth multiplied with velocity gives volume per unit width of water flown. The volume divided with time gives discharge flown.

The dilution method has the major disadvantage that the discharge is estimated directly in an absolute way. It is a particularly attractive method for small turbulent streams, such as these in mountainous areas.