Correct Answer - Option 3 : Slope-area method
Explanation:
Slope area method is an Indirect method of the streamflow measurement technique.
Direct method of Discharge Measurement: There are following method
- Area velocity method
- Moving boat method
- Dilution technique
- Electromagnetic method
- Ultrasonic method
Indirect method of Discharge Measurement:
(i) In this method, we include such technique which find the discharge with the help of relationship between discharge and depth
(ii) The broad classification of this method are:
- Flow measurement structure
- Slope area method
Slope area method:
(i) In this method we find the discharge with help of manning's equation.
(ii) This equation is used to relate the depths at either end of river reach to the flowing discharge in that reach and in this way by knowing the depth, we find out the discharge.
(iii) The selection of reach is the most important part of the slope area method. Following criteria should be followed.
- The accuracy of high water marks must be good.
- The reach should be straight and uniform so far as possible, if it is not possible then choose a gradually contracting section.
- As the length of reach increases, the accuracy in the discharge measurement also increases. A reach length should be greater than 75 times the mean depth.
