Which of the following is a method of conserving water?

Rainwater harvesting is a method of conserving water because it involves collecting and storing rainwater for later use, thus reducing reliance on conventional water sources. This practice can be particularly beneficial in areas experiencing water scarcity or where water resources are limited. By capturing rainwater from surfaces like rooftops, it provides an alternative water supply for irrigation, washing, and other non-potable uses. This method effectively utilizes a natural resource, making it sustainable and eco-friendly.

Other methods mentioned, such as dynamite irrigation, overhead watering, and frequent flooding, do not promote water conservation. Instead, they can lead to water wastage or inefficient water use by either applying water in an uncontrolled manner or through practices that do not optimize water resources.