Rainwater harvesting (RWH) stores rainwater for reuse to supply non-potable uses like irrigation, wash water, toilet flushing, and laundry. During long dry periods the demand will drain the storage cistern down to a critical level where the pressurization pump(s) will need to shut down to prevent dry run damage. Make up water is typically a potable connection to the rainwater harvesting system to supply water, allowing the RWH system to continue to supply the non-potable end use applications until the next storm event refills the storage cistern.
Not done with siting issues yet, maybe this becomes five parts? One issue on siting and design is the hydraulic grade lines. Recall from your road drainage days the equations that were used to space catch pits and throat openings? The equations allowed for you to estimate gutter efficiency and top width for specified design storms. Well, these equations still apply, and I am thinking maybe even more considerations for very low flows.
At about 2.5% of the total water volume on the planet, we’ve always had roughly the same amount of freshwater. Unfortunately, it seems that, at the local level, the amount of fresh water made available through precipitation is increasingly erratic, with the last year featuring historic floods in the eastern US and historic drought in the west. In my adopted home state of California, 2013 was officially the driest year on record and snowpack, groundwater and reservoir levels throughout the state are critically low. Although we’ve undertaken extensive engineering feats in the form of reservoirs, diversions and water supply pipelines, local water management decisions provide our greatest leverage on local water supply.
© 2017 Contech Engineered Solutions LLC, a QUIKRETE Company
In the State of North Carolina, engineering services are provided by Contech Arch Engineering, Professional Corporation.