Consider the followingA stilling well is not required when the stage m...
Explanation:
To understand why option D is the correct answer, let's examine each of the given options and their relevance to stilling wells.
1. Bubble gauge:
A bubble gauge is a simple device used to measure the water level in a tank or reservoir. It consists of a transparent tube partially immersed in the water. When air is blown into the tube, bubbles rise to the water level, indicating the level of water. Since a bubble gauge does not require direct contact with the water surface, a stilling well is not needed.
2. Float gauge recorder:
A float gauge recorder is a device used to measure the water level in tanks, wells, or other water bodies. It consists of a float that moves up and down with the water level, connected to a recorder that records the level. In this case, a stilling well is not required because the float can directly measure the water level without the need for submergence.
3. Inclined staff gauge:
An inclined staff gauge is a device used to measure water levels in rivers, streams, or open channels. It consists of a graduated staff or rod that is inclined at an angle and placed in the water. The water level is determined by reading the height of the water on the staff. Since the staff gauge does not require direct contact with the water surface, a stilling well is not necessary.
4. Echo depth recording:
Echo depth recording is a method used to measure water depth using sound waves. A device known as an echo sounder is used to send sound waves into the water, and the time taken for the echoes to return is used to calculate the depth. This method does not require direct contact with the water surface, so a stilling well is not needed.
Therefore, based on the explanations above, we can conclude that options 1, 3, and 4 are correct. Hence, the correct answer is option D.