This document discusses types of rain gauges used to measure rainfall. It describes non-automatic/non-recording rain gauges like Symon's rain gauge which collect rainfall manually. It also describes automatic/recording rain gauges like weighing bucket, tipping bucket, and float type gauges that record rainfall continuously without manual measurement. Recording gauges provide rainfall intensity over time through a pen on a rotating drum, while non-recording gauges only give total rainfall. Recording gauges do not require an attendant but are more expensive and prone to mechanical faults.

2. HYDROLOGY
Second Term, Final Year
B.E. Civil Engineering

3. Topics
Illustration of various types of rain-
gauges.
Advantaged and disadvantages of
various types of gauges.

4. Types of Rain-Gauges
Following are the main types of rain-gauges used for
measurement of rainfall.
Non-automatic / Non-recording Rain-gauge
Symon’s Rain-gauge
Automatic / Recording Rain-gauge
Weighing Bucket Rain-gauge
Tipping Bucket Rain-gauge
Float type Rain-gauge

5. Non-automatic (Non-recording) Rain-gauge
 These are called non-recording rain gauges because they do
not record the rain but only collect the rain.
 The collected rain is then measured by means of graduated
cylinders so as to directly represent the rainfall volume in cm of
water depth, i.e.
Depth of rain water in cm =
Note: The amount of precipitation/rainfall is expressed as the
depth in cm or inches.
3
2
Volume of water collected in cm
Area of aperatureof the guage in cm

6. Symon’s Rain-gauge
Most common type of non-automatic rain-gauge.
Consists of cylindrical vessel 127 mm (5”) dia
with a base enlarged to 210 mm (8”) dia.
The top section is a funnel provided with
circular brass rim exactly 127 mm (5”) internal
dia.
The funnel shank is inserted in the neck of
receiving bottle which is 75 to 100 mm (3 to 4”)
dia.
Capacity of bottle is 75 to 100 mm of rainfall.
 The rain-gauge is placed in concrete block
60cm×60cm×60cm (2’×2’×2’).
The rim should be 305 mm (12”) above the
ground surface.
Water contained in the bottle is measured by
suitably graduated measuring glass, with an
accuracy up to 0.1 mm.

7. Automatic (Recording) Rain-gauge
 Gauges which can give permanent and automatic
rainfall record without any bottle reading.
 Man has not to go to the gauge to measure the
amount of rain fallen.
 There is mechanical arrangement by which the total
amount of rain fallen, since the record was started,
gets recorded automatically.
 The gauge thus produces a record of cumulative rain
vs. time in the form of graph known as Mass Curve of
rain fallen.

8. Measurement of rainfall by an
Automatic (Recording) Rain-gauge
In general, automatic rain-gauge consists of rotating
drum with a graph paper fixed around it.
There is pen in contact with graph paper, which
moves up with the collected rain, and thus
recording cumulative rain, with the passage of time.
These are of three types
1. Weighing Bucket Rain-gauge
2. Tipping Bucket Rain-gauge
3. Float Type Rain-gauge

9. 1.Weighing Bucket Rain-
gauge
 Consists of a receiver
bucket supported by a
spring or lever
balance or any other
weighing mechanism.
 The movement of
bucket due to its
increasing weight is
transmitted to a pen
which traces the
record on a clock
driven chart.

10. 2.Tipping Bucket Rain-gauge
Consists of 30 cm dia sharp edge
receiver.
At the end of receiver funnel is
provided.
Under the funnel a pair of buckets are
pivoted (the central point which
balances) in such away that when one
bucket receives 0.25 mm (0.01”) of
rainfall it tips (to fall or turn over),
discharging its contents into reservoir
bringing other bucket under funnel.
Tipping of bucket completes an electric
circuit causing the movement of pen
to mark on clock driven revolving drum
which carries a record sheet.

12. 3.Float Type Rain-gauge
 Working is similar to weighing
gauge bucket.
 Funnel receives the rain water
which is collected in rectangular
container.
 Float is provided at the bottom of
container.
 Float is raised as the water level
rises in the container.
 Movement of float is being recorded
by a pen moving on recording drum
actuated by clock work.
 When the water level in the
container rises so that float touches
the top, the siphon comes into
operation, and release the water;
thus all the water in the box is
drained out.

13. Advantages of Recording Gauge over the
Non-recording Gauge.
 In recording gauge rainfall is recorded automatically
& therefore, there is no necessity of any attendant.
 Recording rain-gauge gives the intensity of rainfall @
any time while the non-recording gauge gives the
total rainfall in any particular interval of time.
 As no attendant is required such rain-gauge can be
installed in far–off places also.
 Possibility of human error is obviated.

14. Disadvantages of Recording Gauge over
the Non-recording Gauge.
 It is costly in comparison with non-
recording gauge.
 Fault may be developed in electrical or
mechanical mechanism or recording the
rainfall.