6.2. Non-Recording Rain Gauges

Non-recording rain gauges are simple devices that collect rainfall over a specific period. They do not provide information on the time distribution or intensity of rainfall.

Non-recording rain gauges are basic instruments used to measure how much it has rained over a certain time frame. Unlike recording gauges, they don't track the exact moment rain falls or how heavy it is; they simply collect rainwater. This makes them easier to use but less informative regarding rainfall intensity and duration.

Think of non-recording rain gauges as a cup that you leave outside when it's raining. You can measure how much rain your cup collects, but you won't know when the rain started or how hard it was falling at any moment.

The Symons rain gauge is the standard non-recording gauge adopted by the Indian Meteorological Department (IMD).

Components:

• Cylindrical collector (outer metallic container)
• Receiver (funnel and collecting bottle)
• Measuring jar (graduated in mm)

The Symons rain gauge is a specific type of non-recording gauge recognized for its reliability, especially in India. It has three main parts: a cylindrical outer container that collects rain, a funnel that directs the rain into a collecting bottle, and a measuring jar marked in millimeters for easy reading of the collected water level.

Imagine a funnel that directs water into a bottle. This is similar to how the Symons rain gauge works. The funnel catches rainwater and channels it into a measuring bottle, which shows you how much rain has been captured.

The gauge is mounted on a concrete base with the rim at 30 cm above ground level. It must be placed in an open space, away from buildings or trees.

For accurate readings, the Symons rain gauge needs to be installed correctly. It should be set on a solid concrete base at a height of about 30 centimeters from the ground to avoid interference from surface water. Additionally, it should be located in an open area free from obstructions like trees or buildings that could block rain.

Consider how you might choose an area to set up a tent. You'd want a flat, open space free from overhead branches that could drip rain onto your tent. The same principle applies to placing a rain gauge to ensure it accurately collects water without interference.

Procedure:

• Rainwater is collected in the bottle.
• The collected water is measured daily at 8:30 AM using the graduated measuring cylinder.

The operation of the Symons rain gauge involves collecting rainwater in its bottle. Each day at 8:30 AM, the water is measured using a graduated measuring cylinder, which shows how much rainfall occurred since the last measurement. This daily check helps keep track of precipitation levels.

Think of this process like checking the water level in a fish tank every morning. Just as you use a measuring cup to see how much water you need to add, you measure the rainwater collected in the rain gauge to know how much rain has fallen.

• Cannot record the intensity or time variation of rainfall. • Manual observation required; prone to human error. • Not suitable for remote or automated monitoring systems.

While non-recording rain gauges like the Symons gauge are useful for collecting data over time, they have specific limitations. They cannot provide details about how hard it rained or when the rain started and stopped, which limits their usefulness in understanding rainfall patterns. Additionally, since results are recorded manually, there's a chance of mistakes, and they are not ideal for areas that require automatic measurements.

Imagine a person trying to keep track of their daily steps by writing them down each evening. If they forget, or if they're not precise about their counting, the record will be flawed. Similarly, non-recording rain gauges rely on human observation, which can lead to errors.

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