Rainwater Harvesting

Rainwater Harvesting

By Jason Kulklinski, RLA, CCID; Senior Associate, Norris Design

May 20, 2013

Rainwater Harvesting
Every drop counts. Be water wise. Use only what you need. Slogans for limiting water use are well known in the west and southwest, and the importance of conserving water while creating a beautiful, xeric landscape are a part of Norris Design’s philosophy. Rainwater harvesting has become one of the more popular trends in sustainable development. In fact, many municipalities are considering or have passed legislation that requires efficient landscape water usage. According to the Environmental Protection Agency (EPA), 29 billion gallons of water is used daily by households in the US of which 7 billion gallons or 30% is devoted to outdoor water use. In more arid climates, like in the west and southwest, a household’s outdoor water usage can jump up to 70%.

This trend has led some communities to mandate the implementation of rainwater harvesting systems, both passive and/ or active. The City of Tucson, Arizona has adopted a Rainwater Harvesting Ordinance which requires that all commercial development must utilize 50% of their budgeted potable water allotment from harvested rainwater for landscape irrigation or face fines. At Norris Design, we take a proactive project-by-project approach to develop a design and evaluate the most cost-effective way to incorporate proper rainwater harvesting techniques or systems and efficient water conserving landscape irrigation designs.

What is Rainwater Harvesting?
There are two types of rainwater harvesting that can be incorporated into your project. The first is passive rainwater harvesting. Passive rainwater harvesting is a process by which the landscape design uses contouring of the site to direct and capture rainwater into small depressed areas or mirco-basins. Many techniques are utilized to direct the flow of rainwater run-off, such as creating curb cuts into landscape islands, curbless parking lots, directing roof run-off and heating evaporative to landscaped micro-basins. Many believe this is an accepted approach to maintaining a healthy native landscape with little to no supplemental water or irrigation because the majority of the precipitation occurs during the hottest, driest months when the native plants have the greatest water requirement.

Another type of rainwater harvesting is active rainwater harvesting, which may include a cistern or tank, first flush filtration device and some distribution device such as a hose or dripline. More complex active rainwater harvesting systems include pump systems, large storage tanks or cisterns, water treatment, filtration, control systems and cross-connections to the municipal water system. Active systems allow the storage of water for irrigation use over extended periods of time.

Challenges and Opportunities
There are challenges with the creation and implementation of any new technology or process, including existing water legislation in states like Colorado. Other significant challenges include the lack of regulation for proper design and installation to protect the health, safety and welfare of the public, the lack of experience and education for professionals to design rainwater harvesting systems, limited equipment and product resources, a lack of experienced contractors for system installation and a lack of training for facility managers and system maintenance. The biggest challenge, similar to most green development solutions, is that the return on investment will not be realized for many years.

Norris Design is an industry leader in the design and implementation of rainwater harvesting techniques. We realize the opportunity to reduce water use, design creatively while being conscious stewards of our resources. We begin each project by evaluating client goals, jurisdictional requirements and budget to develop a rainwater harvesting approach and irrigation system that conserves the use of potable water for landscaping. Norris Design works collaboratively with each design team member to implement passive and active rainwater harvesting techniques that result in an overall reduction in landscape water usage. We also work tirelessly with equipment suppliers and property owners and managers to train the end-user on the systems operation and maintenance. Proper design, operation and maintenance are critical to protect the investment in the system and to realize the potential energy and water cost savings.

Case Study :: Blue Moon Community Garden at the Tucson House
Tucson, Arizona

Project Highlights
Norris Design, in collaboration with KC Mechanical, Ewing Irrigation, City of Tucson Planning and Community Development Department and M. Anderson Construction, designed a successful rainwater harvesting system for the Blue Moon Community Garden at the Tucson House. The garden is being utilized as a demonstration garden and irrigation/rainwater monitoring site. Design goals included:

• Harvesting rainwater both actively and passively
• Incorporating monitoring devices to track water use
   - Determining the cost of a gallon of harvested rainwater based on power and infrastructure cost,
• Tracking maintenance schedule/lifetime of passive rainwater harvesting basins
• Determining the accuracy of the budgeted plant water requirements through the use of soil moisture sensors
• Determining if there is the potential to save water in additional Community Gardens of Tucson sites.

The Blue Moon Community Garden project site is approximately 1 acre. The proposed active rainwater harvesting system incorporates two (2) major collection areas for the active rainwater harvesting system; 6,000 square feet of the southeast corner of the existing Tucson House building and 300 square feet comprised of 1/2 of the proposed ramada roof. Norris Design developed interpretative signage that included information on Tucson’s rainfall, rain seasons, passive and active rainwater harvesting systems and how they have been implemented in the garden.

Rainwater Harvesting Systems
The active rainwater harvesting system collects water from the roof of the Tucson House building and the ramada structure. The total roof area from the Tucson House is approximately 6,000 square feet, which can collect an average of 45,000 gallons of water per year (based on the average of 12” of rain per year). The ramada roof collection area is approximately 300 square feet, which can collect approximately 2,200 gallons of water per year.

The garden has been designed to take advantage of the existing grading which slopes southeast to northwest. Passive rainwater harvesting basins have been design to capture site sheet flow. One half of the ramada roof has been design to drain into a passive rainwater harvesting basin adjacent to the ramada to demonstrate passive rainwater harvesting techniques.

Norris Design in conjunction with KC Mechanical and the general contractor tapped into the heating and cooling system to monitor and collect for storage. A flow meter was placed on this connection to determine the amount of condensation generated by the cooling system and added to the total collected water on site for landscape irrigation.

To monitor the electricity usage and cost, a separate electrical meter has been specified by the electrical engineer to track the electrical use of the following; rainwater harvesting pumps, irrigation brain boxes and irrigation controller.

The rainwater harvesting and irrigation design has incorporated flow meter/sensors which tracks water usage through a mechanical dial much like a potable water meter but also works in conjunction with irrigation controller to shut down the irrigation system when there is an abnormal flow (i.e. a break in the irrigation line).

Soil moisture sensors have been located in the community garden beds, citrus grove and a passive rainwater harvesting basin. The soil moisture sensors are installed at a depth within the root zone of the proposed plant material or the bottom of the passive rainwater harvesting basin to indicate to the controller not irrigate if there is water present at said depth of the soil within the root zone depth. This would typically occur after a rain event thereby saving water by not irrigating after a rain event.

The Baseline irrigation controller is a smart controller which offers multiple smart watering modes, complete flow management, soil moisture sensing and a multitude of programming options. The irrigation controller will learn flow and provide alerts of low or high flow scenarios and shut down in a rain event. For additional yearly cost, the controller can be monitored remotely via a desktop or laptop.

If you would like to discuss how to incorporate rainwater harvesting into your next project, please give us a call at 303.892.1166. We look forward to discussing how to make your next project more efficient, beautiful and sustainable.