JNTU B.Tech III WATER RESOURCES ENGINEERING-I Previous Question Paper (October - 2020 - R13)

The weighing bucket rain gauge operates on the principle of measuring the weight of accumulated precipitation over time. It consists of a collector funnel that directs rainfall into a bucket resting on a spring-loaded platform or a counterbalanced lever system connected to a recording mechanism.

As rain falls into the bucket, its weight increases, causing the platform to move downward. This movement is transmitted through a mechanical linkage to a pen arm. The pen records the vertical displacement on a clock-driven rotating drum covered with a chart paper. The vertical axis of the chart represents the cumulative depth of rainfall, while the horizontal axis represents time. When the bucket reaches its capacity, it is typically designed to automatically empty via a siphon or a mechanical trip, allowing the pen to return to the zero position and continue recording.

Advantages:

• It provides a continuous, permanent record of rainfall intensity and duration.
• It can record all forms of precipitation, including snow, hail, and sleet, as it measures mass rather than volume.
• The data is easily accessible for analysis of storm patterns and intensity-duration-frequency curves.

Disadvantages:

• The mechanism is complex and requires regular maintenance and calibration to ensure accuracy.
• It is more expensive to install and operate compared to simpler non-recording gauges.
• The moving parts are susceptible to mechanical failure or friction errors if not properly lubricated and protected from environmental factors.

Sketch Description: The apparatus features a cylindrical outer casing containing a funnel at the top. Below the funnel, a bucket sits on a platform connected to a spring balance. A pen arm attached to the spring mechanism rests against a clock-driven drum. As the bucket fills, the spring compresses, moving the pen upward to trace the cumulative rainfall curve on the rotating chart.