Pump test at Cubbon Park

 

On 21^st May, 2017 while the TCS World 10k was ongoing, a group of 11 workers from Peddanna’s Rain water harvesting were enthusiastically carrying out their work of cleaning the well. TCS world 10k during its 10^th edition had announced ‘give back’ to the city which gave rise to The Cubbon Park Rejuvenation project. The scientific support is given by Biome Trust, a leading water conservation and eco-architectural firm.

A total well cleaning is an excellent opportunity to carry out pumping test. A pump test a.k.a Aquifer test has two parts which includes the flow test and aquifer recharge test. In the flow test, the amount of water drawn out is monitored along with fall in water level in the well at certain interval. Well Peddanna used a 3 horse power motor pump to pump out water and it took approximately 6 hours to drain out the well 12 feet diameter and 25 feet of water, the total depth of well is 40 feet.

Aquifer recharge test is done by draining out all the water from the well and checking the amount of water rise after 24 hours. Another way of doing this would be continuous monitoring at fixed interval until the initial water level is achieved after a complete drawdown. These being manual methods, there are more technically advanced methods incorporating sensors that would help in continuous monitoring and reporting without one being physically present at the site.

Cubbon park has 7 open well, depending on the dimensions, each holds more or less 60,000 liter of water. Water from the well will be used for watering the rose garden around the state central library.  So back to pump test, which was done from 20^th to 22^nd May, 2017. The total time taken to pump it the water was 6 hours when the water level around 18 feet with average of 3 feet per hour of drawdown. The recharge of the well was checked after 24 hours. The water recovered to 8 feet in 24 hours i.e 25,620 litre.
The significance of aquifer recharge test is to estimate the amount of water that can be drawn per day. Below are the observation as recorded during the study:
 Initial water depth : 18 ft Initial volume : 57,645.9 litre

Time Interval (From-To)	Drop in level (ft)	Volume Extracted (litre)
1 hour (8-9a.m)	4.3	13,771.1
1.5 hours (9-10:30am)	4.1	13,130.5
1 hour (10:30-11:30am)	3.5	11,208.9
1 hour (11:30 am- 12:30pm)	3.2	10,248.1
1.5 hours (12:30-2:00pm)	2.9	9,287.3

Water level after desilting and removing debries : 0.54ft

Volume of water after complete draw down : 1500 l (approximate as the surface was not even)
A major interference in aquifer recharge test is that the water that was drawn out during the clean up was let out in the close proximity. A further study is necessary in different season to estimate the recharge capacity acurately throughout the year. This study would be essential to determine and plan the amount of water that can be withdrawn during each season.