Maintenance- the following steps should be adopted to ensure quality of harvested rain water:
Impact assessment will help you answer the following questions:
Monitoring for quality- Quality of water harvested can be monitored by sending water samples to labs for testing or using easily available water testing kits.
Monitoring for quantity- Monitoring quantity of rain water harvested will help you provide concrete evidence of the impact of rainwater harvesting. If the data is positive it will help to catalyse other people to follow in your footsteps. A monitoring system will help determine:
Groundwater recharge rate can be calculated using water level monitoring or infiltration test. It is recommended that the monitoring be done monthly especially pre and post-monsoon. If ground water is being extracted monitoring extraction from tubewell will give you total extraction based on the formula = Hours of pumping X yield of tubewell
Using a water level indicator- The water level indicator consists of a probe, a graduated cable or tape, and a cable reel with built-in electronics. The probe is lowered down the standpipe until a buzzer indicates contact with water. Depth-to-water measurement is read from cable or tape. Regular monitoring will show trends for the impact of RWH. It takes few years to show tangible outputs.
Infiltration or recharge rate test- A simple test to know the exact recharge rate from the recharge wells. Use a water meter to measure the level of water flow into the recharge tank followed by continuously monitoring of the level of water in the tank.
CSE has been regularly monitoring water levels in all its model RWH projects. It was found that in places where rainwater harvesting was undertaken, the water levels had not declined. In the same period, there was a general decline in the water table in the areas of Delhi where the model projects were situated.
In order to monitor the quantity of water being used, the following audit should be carried out: