Rainwater Harvesting at the NAU ARD Building


The ARD Team

Porject Description

Design Process

Site Location

Precipitation Analysis

Water Consumption

Rooftop Analysis

Sizing and Location

Water Distribution

Applicable Regulations



Water Consumption

SSLUG Community Garden

When the ARD building was completed in 2007, there were plans to landscape and beautify the storm water detention basin that stands in the foreground of the site.  Due to budgetary reasons the landscaping was never completed, and as it stand the basin is filled with weeds.  Recently, grant money was awarded to the Sustainable Communities Program at Northern Arizona University to re-landscape the detention basin using native as well as other plants well suited to Northern Arizona.  As a part of this plan Students for Sustainable Living and Urban Gardening will be building an urban garden on the site.

Water Availability for the Garden

At this time the only water available for use in the garden is treated wastewater which is used for irrigation on most of campus.  The preferred method of irrigation, however, would be harvested rainwater from the roof of the ARD building.  Because planting season coincides with Flagstaff’s dry season of the year, water for the system will have to be collected and stored prior to the beginning of Flagstaff’s short growing season. 

Plant Varieties

The Plants that will be used for the storm water basin have yet to be chosen by the groups on campus involved in this project.  It is expected that a number of plants native to Northern Arizona and the Colorado Plateau will be used for the overall beautification of the basin.  There may, however, be use of other non-native plants that are well suited to high altitudes.  Because of the focus on sustainability for this project the plants chosen will most be drought tolerant, and require little to no irrigation.  The plants in the garden are also expected to be native edible plants that will require little irrigation. 

Garden soils

The soils that are predominant in Northern Arizona range from volcanic to clayey soils.  These soils are not ideal for gardening.  Therefore, in order to have the best conditions possible for gardening, compost and gardening soils will have to be used.  The porosity of the native soils are in the range of 0.4 - 0.6, while the porosity of a gardening soil is in the range of 0.8 – 0.95. For our calculation of the volume of water that will soak into the soil we chose a porosity of 0.7 which falls in between these two ranges.  For this choice we assumed that the soil would be a mixture of the native soil and gardening soils, and that there would be some compaction to offer stability for the plants to root.

Water Needs for a Small Community Garden

The minimum volume of rainwater needed for the community garden during the dry season will be the use of 1 in. of water weekly over the gardening area.  The watering area will be the sum of the areas of evenly distributed raised beds. Each raised bed is a 4 x 12 ft. box with an area of 48 ft2, and there are a total of 15 raised beds.  The expected volume of water that will be used weekly is approximately 450 gallons.  For a gardening period of 3 months, or approximately 12 weeks the expected total volume needed is 5400 Gallons.