Measurement of Depth of Water
The depth of water is measured by the subsequentmethods are given bellow. of hydrographic survey.
The depth of water is measured by three methods:
1. Sounding Rod
It is a wooden or bamboo pole of 5 cm diameter and two and half meter length. it’s given a disc of 15 cm diameter at rock bottom . it’s graduated in metres and 1/10th of a metre.
The sounding rod is suitable for measuring the depths of small rivers, of the order of two meters.
o live depth, the sounding rod is slowly immersed vertically from a ship , at the specified place, in order that the bottom plate just touches the bed of the river.
The level of water is then noted from the graduation (Fig. 13.6).
2. Sounding Cable
When the depth of water is quite 2 m and water current is high, the speed rod isn’t practicable.
Hence this case, a cable or rope is released slowly from a ship by means of a pulley system (Fig. 13.7).
The cable Comprise of a counter weight of about 5 kg.
When the load just touches rock bottom of the river, a mark is formed on the cable exactly at the water level. Then the depth is measured by tape.
The echo-sounder is employed for measuring depths of enormous rivers, in way over 10 m, and people of seas.
It’s an electrical instrument, during which a sound impulse from the surface of water is shipped towards the bottom level of the river or sea (Fig. 13.8).
The sound waves are reflex back from the bed in the form of an echo which is arrested by the receiver.
There is an automatic recording of the time of onward and backward travel of the acoustic wave .
Taking the speed of sound in water to be approximately 1,470 m/s, the depth of water will be computed.
Generally, the echo-sounder is placed just at the water level to eliminate transmission loss and acquire an accurate result.
Here in this post we have covered the three methods to measure the Depth Of Water.