Substituting stored rainwater for regular tap water to irrigate can help reduce outdoor water use, which can have far reaching environmental benefits. Water conservation reduces water demand, which allows rivers and streams to maintain adequate water levels and flow. This helps to sustain healthy aquatic ecosystems. Conservation also reduces the need to develop new water treatment and new water storage - a process that often causes unfavorable environmental repercussions. Additionally, conservation reduces the need to overdraw from groundwater resources, which can be vulnerable to depletion and contamination. Indirectly, saving water also helps to reduce energy consumption.
Figure 1: Adequate stream flows are necessary to maintain healthy aquatic ecosystems. Photo source: Aquacraft, Inc.,