Goa University shows state how to harvest rainwater

What started as an effort to showcase rainwater harvesting methods and their benefits at Goa University, has now become an effort worth emulating by the entire state.

Aquifer recharge and RWH project at Goa University

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29 Jun 2014, 3:48 am

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As a faculty of the Earth Sciences Department at Goa University, Dr. A.G Chachadi wanted to develop a facility to harvest rainwater and recharge groundwater at the campus at Taleigao Plateau. He wanted to showcase rainwater harvesting within the campus and also spread awareness on the benefits of doing it.

Initial calculations showed that groundwater at the University campus was pumped out at a rate of about 250 m3 per day from all the 7 operational borewells for about 300 days in a year. That totals about 75000 m3 of groundwater every year. He did a simple calculation to understand how much rainwater could be harvested before implementing the system.

Total drainage area contributing surface runoff = 30000 m2
Daily average monsoon rainfall in the area = 0.02m/day
Surface runoff collected per day (50% of rainfall) = 300m3
Estimated recharge to sub-surface thru borewell = 250m3
Ratio of aquifer recharge to runoff collection= 250/300 = 83%
Amount lost due to seepages, evapo-transpiration and other factors = 17%

The well yield tests carried out on two borewells located in close proximity of the present recharge structure in May 2008, that is after one year of operation of the first recharge structure, have confirmed that there is an increase in the well yields by 13% to 15%.

Device to measure groundwater recharge. The well yield tests carried out on two borewells located in close proximity of the present recharge structure in May 2008, that is after one year of operation of the first recharge structure, have confirmed that there is an increase in the well yields by 13% to 15%.

How does the system work?

At the site, the rainwater falling on the ground is collected into a 70m x 50m size depression using gravity flow. The structure has three parts of which the first part with a size of 20m x 10m and depth of 2m allows the suspended solids to settle down.

Schematic diagram of the surface runoff harvesting system

Overview of the structures

The rainwater harvesting structures built in the campus have minimum maintenance activities and recurring costs. The various annual maintenance activities include:

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rainwater_harvesting_for_aquifer_storage_recovery.pdf

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urban_rainwater_harvesting_report.pdf

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Groundwater