Many practitioners separate water harvesting into two major categories—passive water harvesting and active water harvesting. Sometimes these two groups are called simple (passive) and complex (active) water harvesting. Very simply, passive water harvesting works by shaping the earth to slow the velocity of runoff, infiltrate it into the soil, and direct it to where it can be beneficially used by vegetation. Active water harvesting, in contrast, uses rain barrels, cisterns, and other types of containers to store rainwater for later distribution. The stored water can be used outdoors to irrigate vegetation or indoors for non-potable (toilet flushing, laundry washing) and potable (with extensive filtration and disinfection) uses. Active water harvesting systems can “extend” the rainfall season and maximize the use of collected water, but are also significantly more expensive than passive systems. The payback period for active systems can be quite long, especially in areas with low costs for water.
Keywords: water harvesting, active, distribution, first flush, barrel, tank