Cierto: Channel Islands Environmental Rain Technology Options
Six rain barrels of varying capacities were installed across campus as a case study to investigate the feasibility of installing barrels campus wide. While the costs of purchasing these already prepared barrels were significant, the internal costs of prepping and installation would have been a fraction of this cost.
KEYWORDS: rain barrels, precipitation, runoff, storm
Rain barrels are a centuries-old technique used by many cultures to collect rainwater from rooftops for later use or consumption. In a Mediterranean climate where water is a precious commodity, rainfall and in turn rainwater availability is often highly variable. Typically, there are years of significant rainfall followed by years with little rainfall. Collected rainwater may help ease the burden of this inherent variability in our local climate. In addition, these systems bolster groundwater infiltration by capturing water that would otherwise become storm runoff.
The extent of southern California's climate variability is shown in Fig 1. The "year" for this data set is the water year. A water year runs from October 1 to September 30. The maximum amount of rainfall in the previous decade was 82 cm in 2005, nearly four times the precipitation that fell in 2004 (21 cm). Few years are near the mean of 34 cm, illustrating the difficulty of predicting the amount of rainfall. >The median is 28 cm, six cm less than the mean.
Nezlin and Stein (2005), found that rainfall from 1996 to 2003 averaged 37 cm, with a maximum of 83.73 cm in 1997 and minimum of 14.82 cm in 2001. The mean for 2002-2013 and 1996-2003 differ by three cm.
California State University Channel Islands (CSUCI) is expanding as the student population increases. The university is trying to become more sustainable and currently, one option the campus is exploring is using reclaimed water. During the period of July 2011 – June 2012, CSUCI reported a total use of nearly 7.5 million L of reclaimed water on the Anacapa Hall meter. The minimum water usage was in September 2011 at 254,851 L and the maximum water usage was in June 2012 at 1.47 million L. Though the campus utilizes native landscaping and xeriscaping to reduce water consumption, water usage generally spikes during dry months.
In February 2013 we installed six rain barrels of varying capacities were at three separate locations on the campus of California State University Channel Islands (CSUCI). We installed two wooden barrels around the "C" building of Anacapa Village and one wooden barrel near the pool (Fig 2). According to the manufacturer, these barrels have a capacity of 53 gallons, approximately 200 L. Two plastic barrels with a capacity of 220 L were installed on the side of Napa Hall. One wooden barrel with a capacity of 200 L was installed in Malibu Hall. This barrel also included two rain chains.
The installation methods for the barrels differed depending on the type of barrel. The rain chain barrel required the downspout to be cut and a hook installed. This allowed the rain chains to be easily attached and removed. The housing barrels, excepting the one outside of housing, were attached via a rain water diverter. The downspouts were directly attached to rain barrel outside of housing and the Napa Hall barrels.
Once the barrels were installed, the water levels were measured after rain events or after draining the barrels. A hole was drilled in the top of the barrel and a wood dowel was placed in the barrel. It was rotated gently to ensure that the water made a clear distinction between the wet and the dry part. The dowel was then removed and the wetted segment measure to the nearest 0.1 cm.
Locations of rain barrels on CSUCI campus.
The two rain chains connected to the rain chain barrel.
We developed a computer program, CIERTO barrels, to estimate the actual volume of water within wooden barrels and the plastic barrels. The wooden barrels needed several measurements to approximate the general volume. The arc height and circumference were measured to estimate the radius and height, and subsequently, the volume. We tried minimizing error by accounting for the thickness of the barrel and the spacing at the top and bottom to better estimate the actual volume. The error in the program is approximately six liters. A minimum value of 10 cm is necessary for the program to work.
This project was successful in giving insight to a rain barrel program campus wide.
Rooftop areas were measured from the CSUCI campus master plan map and multiplied by rainfall totals to give an estimated volume of rooftop runoff. The total amount of roof area in Anacapa, excluding the housing office, was approximately 3840 m. For a two cm storm, that is approximately 76,860 L. Table 1 includes the rooftop areas that drained into the rain barrels. These volumes are clearly insufficient to completely offset campus reclaimed water usage. However, they are significant enough to contribute to a reduction in consumption, particularly if water collected in wet months can be used to offset peak usage during the dry summer months.
March 10, 2013 Rain Event
March 10, 2013 Rain Event Capture Efficiency
As we have only recorded three rain events, it is difficult to draw any robust conclusions. For a more extensive analysis, at least a full year of data is necessary. It is recommended that data collection continue for more than a year to support any conclusions as the annual precipitation is not consistent. Furthermore, research on the capture efficiency of the rain chains is also desired.
Rain barrels are working well to date, but we will likely need another full rain year to test our rates of return and perfect our estimates of water diverted from storm drains following a full build out of rain barrels across campus. Furthermore, our theoretical capture amounts differ significantly from our actual capture amounts [Table 2]. Some of this is definitely due to the way the barrel is attached. But for those directly attached, future research should focus on why the capture efficiency is so low.
Our purchase cost of the plastic barrels was $150. The purchase cost for the rain chain barrel and the other wooden barrels was $350 and $375 respectively. If wooden barrels or other plastic drums were donated, students can build the barrels themselves for a fraction of the cost. All costs estimates are from Home Depot. The cost for the EarthMinded DIY Rain Barrel Diverter and Parts Kit is $26.98. A rubber stopper should also be included to take measurements. In order to make a rain chain barrel, only spigot ($5.30), an overflow ($7.96), and the rain chain. There is leftover mosquito netting that can be used for this project. Otherwise, mosquito netting can be purchased for $16.44 which will likely cover five barrels.
Wooden barrels require some water to remain in the barrel at all times since the wooden shrinks and swells. While plastic barrels do not have this drawback, when students and faculty were asked which barrel they preferred, the wooden barrels were overwhelmingly popular. For future projects, wooden barrels are recommended.
This is a project that students should continue, with some alterations. Assuming that there are 12 campus buildings and three wooden barrels were installed at each building, if:
- Manufacturer prepared barrels were installed, the internal cost would be $13,500.
- Student-constructed barrels were installed, the internal cost would be $944.
- Student prepped barrels are 7.2% of the cost of the manufacturer prepared barrels.
For future barrel installations, our recommendation is that the barrels are student made. This offers not only hands on experience for students, but is also a more fulfilling project as students can apply these skills for their own gardens.
We would like to thank CSUCI's Instructionally Related Activities and California State Student Association for providing funding. We would also like to express our gratitude to CSUCI's Department of Facilities Services crew for quickly installing the barrels. We would like to thank Cameron Embree from CSUCI's Science, Technology, Engineering and Mathematics Center for the computer program. We also thank our Gloria Ramirez and Janine Hernandez for their assistance, and Todd Saunders for data collection.
CNRFC, N. s. N. W. S.-. 2005. California Nevada River Forecast Center.
Nezlin, N. P. and E. D. Stein. 2005. Spatial and temporal patterns of remotely-sensed and field-measured rainfall in southern California. Remote Sensing of Environment 96:228-245.
1 Environmental Science and Resource Management Program, CSU Channel Islands.
3 Faculty Advisor: Sean Anderson email@example.com