Date: 09/15/2015

Final
Residential Precipitation Collection

WATER RESOURCES REVIEW COMMITTEE

Votes: View--> Action Taken:
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10:00 AM -- Residential Precipitation Collection

Reagan Waskom, Director, Colorado Water Institute, introduced himself to the committee, and gave a brief overview of the presentation. He also introduced his fellow presenters, Dr. Larry Roesner, Colorado State University (CSU) Professor of Civil and Environmental Engineering, and Chris Olsen, Director, CSU Stormwater Education Program. He explained that he and the fellow presenters do not have a position on any legislation, but are rather advocating for efficient water management.

10:06 AM

Dr. Roesner introduced himself and iterated that he does not have a position on any legislation. His presentation (Attachment A) was distributed to the committee prior to the meeting. Mr. Roesner explained that his presentation would provide an unbiased assessment of the effects on runoff and infiltration of 100 gallons of rainwater capture capacity for a typical household using defensible scientific methods and Colorado-specific (Denver) climatic conditions. Mr. Roesner described the methodology of a recent study that determined the effect two rain barrels on a residential lot would have on surface water runoff. He explained that the study determined that there was no significant or measurable difference in the runoff of a developed lot with rain barrels. Mr. Roesner identified rain barrel adoption rates in other states and estimated that there would be approximately a 5 percent adoption rate of rain barrels in Colorado if allowed. Dr. Roesner explained that allowing 100 gallons of rainwater storage per household will not decrease surface runoff by any detectable amount on a typical lot. Development on previously undeveloped land (“greenfield”) has a significantly greater effect on surface runoff and infiltration than rainwater storage.

Attachment A.pdfAttachment A.pdf

10:15 AM

Mr. Olsen answered questions from the committee regarding the impact of rain barrels on surface runoff. He explained that there is not a difference in the amount of runoff because water captured in rain barrels would have evaporated or been consumed by vegetation. Mr. Olsen and Dr. Roesner responded to questions from the committee about the calculations that lead to the determination that rain barrels have an insignificant affect on stream flows. Dr. Roesner explained that creating an augmentation plan for rain barrels would be difficult because their effect on streamflows is so small. In response to another question, Mr. Olsen explained that because the amount of surface runoff does not change with the use of a rain barrel, there would not be a measurable impact if more people used rain barrels. Mr. Olsen responded to questions regarding the adoption rates of rain barrels in other states; and explained that the City of Milwaukee collects data on the sale of rain barrels to estimate their impact on runoff. Mr. Waksom responded to questions from the committee regarding the way in which the water captured by rain barrels is used and why it would be difficult to calculate their impact on stream flows.