Influx of irrigation water
The cycle begins with input of fresh irrigation water, this is often referred to as the primary water supply for the greenhouse. Preferably this should be rain water collected from the roof. When the amount of rain water is insufficient (and/or storage is too expensive), alternative primary water supplies can be used such as ground water (which is sometimes called “well” or “bore” water), surface water or tap water. However, this water must comply with quality requirements for use in a hydroponic system (See also download "Best Practice Guidelines for Greenhouse Water Management").