Landscape architects serve an important role in the conservation and re-use of water. An l.a. should question how rainwater, groundwater and “waste” water will be managed on every project because water is too valuable to let it go down the drain.
On architectural projects we have found that capturing rainwater from the building roof is imperative so that stormwater runoff rates are not increased by the new development. This water from the roof can be detained temporarily and slowly released or it can be retained and re-used for another purpose. In many parts of the country, groundwater re-charge is important, so the captured rainwater is held until after the storm event and then slowly released back into the ground, so the addition of the building does not impact the groundwater levels.
Where groundwater levels are less of an issue, the rainwater can be collected and stored in a cistern for re-use for landscape irrigation or water features. If coordinated early with the project architect, no additional plumbing is required within the building to capture the rainwater. All that is required is a cistern constructed from a concrete tank, drainage pipe, or other chamber system. An irrigation pump then will supply the stored water to the irrigation system. Rainwater used for irrigation is much better for plants than potable water that has been treated with chlorine and other chemicals.
In areas where there are high water tables, groundwater may be pumped from below the building basement or slab and disposed of. This water should be tested to see if it is appropriate as a water supply for landscape irrigation.
Another potential supply of “waste” water in a building relates to the HVAC system. Air conditioning systems produce high volumes of excess water that is clean and pure, thus suitable for re-use for landscape irrigation or groundwater recharge.
Heating systems also can produce water, but the water quality should be tested before it is re-used. Depending on the heating system the water could be condensation that is relatively pure or it could be acidic. It is unlikely during the heating season when this water is produced that there is demand for landscape irrigation, so this water could be a source to re-charge groundwater.
by Kyle Zick, ASLA