Active and Passive rainwater harvesting

Active rainwater harvesting requires a person, switch or valve to actively turn it on/open or off/closed. The more active a system, the more energy it requires. The best example of this are storage tanks or cisterns that collect rainwater from roofs. This allows you to store the water for when you need it, like summer, to be used to water plants or anything else. The downside is these systems tend to cost more than earthworks and limit your storage capacity to the size of the tank.

Active rainwater harvesting system - one of our ferrocement tanks

Passive rainwater harvesting freely works without the need of a person, switch or valve. The more passive a system, the less energy it needs.  Earthworks, simple structures and strategies that change the topography and surface of the soil, are a great example of this system. They can speed the infiltration of water, augment soil moisture and nutrient availability and provide large quantities of high quality rainwater to gardens and landscapes. Water can be collected in huge amounts from roofs, streets, vegetation, bare dirt or greywater drains. This water is only available for limited periods after rainfall depending on soil type, mulch, climate and plant uptake but it can recharge groundwater.

Something as simple as applying a layer of mulch around your plants can reduce water usage by 25%, creating a passive system.

Passive rainwater harvesting at our education and demonstration site