Borehole yield and use of the Bucket Pump

Borehole Yield and Use of the Bucket Pump

The yield of boreholes in volcanic rocks of Maharashtra is
generally low, rarely exceeding 2000 liters per hour. For the use
of the hand-pumps (Mark II (see photo) or Mark III pump) a borehole supplying
less than 500 liters per hour is considered to have a poor yield,
and wells supplying between 500 and 1000 liters per hour are a
good yield, if supplies more than 1000 liters per hour is
considered to have a good yield. Boreholes with less than 500
liters per hour may be subject to high water level fluctuations
and yield little water during the driest months. Those with good
yield generally supply water all year round, even if the water
level is subject to fluctuations during the dry season.
Boreholes with more than 1000 liters per hour are considered by
the Ground Water Survey and Development Agency (GSDA) suitable
for the installation of electrical pumps if villages have a
population of at least 500 people; for smaller villages, GSDA
currently installs Mark III hand pumps.

The water level fluctuation is related not only to the yearly
rainfall regime, but also to a number of other factors such as
the geo-morphological conditions of the area where the borehole
is sited, the number of people supplied by the well, and the
depth of the water entries. Boreholes with shallow water entries
are generally subject to greater water fluctuation than those
that struck deep fissures.

It appears clear that the criteria for the installation of a
bucket pump has to be based upon all the factors mentioned above;
in addition, special consideration should be given to the
relation between depth of the water level versus well yield.

All the above aspects will be also useful for defining the length
of the wire rope (the length of the wire rope in the 27 boreholes
equipped with bucket pumps varies from 32 to 60 ft). A wire rope
longer than 60 ft would create too much stress on the people and
lessen its duration.