Step 1: Understanding the Concept:
The question asks to identify a water flow measurement device that is particularly suitable for use in channels carrying water with a high sediment load (silt) or floating debris. This means the device should be resistant to clogging.
Step 2: Detailed Explanation:
Let's analyze the susceptibility of each device to clogging:
(A) Orifice: An orifice is a small, submerged opening with a sharp edge. It is very susceptible to being clogged or having its effective area changed by suspended sediment and floating debris, which would make its readings inaccurate.
(B) Weirs: A weir is a dam-like structure over which water flows. It has a sharp crest. Sediment can accumulate upstream of the weir, changing the approach conditions and affecting accuracy. Floating debris can get caught on the weir crest, also disrupting the flow and the measurement.
(C) Parshall flume: A Parshall flume is a type of open-channel flow measurement device that works by constricting the flow. It has a converging section, a narrow throat, and a diverging section. A key feature of its design is that it has a smooth, unobstructed floor and walls. This design, combined with the increase in velocity as water passes through the throat, creates a "self-cleaning" action. The high velocity tends to scour away any deposited sediment. Because there is no sharp crest or small opening for debris to get caught on, it is very resistant to clogging and is the preferred device for measuring flow in natural streams and irrigation channels that carry silt and debris.
(D) Water meter: This typically refers to a mechanical device with a propeller or turbine placed in a pipe. The moving parts are very vulnerable to being damaged or clogged by silt and debris.
Step 3: Final Answer:
The Parshall flume, due to its self-cleaning properties and open design, is the water measuring device that does not easily get clogged by silt or debris. Therefore, option (C) is the correct answer.