Rainwater Harvesting Potential Bangalore


blog7The total amount of water that is received in the form of rainfall over an area is called the rainwater endowment of that area. Out of this, the amount that can be effectively harvested is called the water harvesting potential. Among the several factors that influence the rainwater harvesting potential of a site, climatic conditions especially Rainfall and the catchment characteristics are considered to be the most important.

Rainfall Quantity: Rainfall is the most unpredictable variable in the calculation and hence, to determine the potential rainwater supply for a given catchment, reliable rainfall data are required, preferably for a period of at least 10 years. Also, it would be far better to use rainfall data from the nearest station with comparable conditions.

Pattern: The number of annual rainy days also influences the need and design for rainwater harvesting. The fewer the annual rainy days or longer the dry period, the more the need for rainwater collection in a region. However, if the dry period was too long, big storage tanks would be needed to store rainwater. Hence in such Regions, it is more feasible to use rainwater to recharge groundwater aquifers rather than for storage.

Bangalore is blessed with a relatively well distributed rainfall and has a rainfall distribution which is Bi-modal (Two peak rainfall seasons in a year). In this context, the following strategy has been found most suitable for rainwater harvesting implementation in Bangalore:


Parameter Measure
Total Annual average rainfall 970 mm
Total no of rainy days 60 rainy days
Peak hour intensity of rain in Bangalore 60 mm/hr


The rainfall distribution pattern in Bangalore
JAN 0.2 2.70
FEB 0.5 7.20
MAR 0.4 4.40
APR 3.0 46.30
MAY 7.0 119.60
JUN 6.4 80.80
JUL 8.3 110.20
AUG 10.0 137.00
SEP 9.3 194.80
OCT 9.0 180.40
NOV 4.0 64.50
DEC 1.7 22.10
TOTAL 59.8 970.00
AAverage annual Rainfall (in mm) In Karnataka
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