Goa University shows state how to harvest rainwater
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%
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.
The rainwater harvesting structures built in the campus have minimum maintenance activities and recurring costs. The various annual maintenance activities include: