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Water balance monitoring for two bioretention gardens in Omaha, Nebraska, 2011–14

Scientific Investigations Report 2015-5188
Prepared in cooperation with Douglas County Environmental Services and the Nebraska Environmental Trust
By: , , and 
https://doi.org/10.3133/sir20155188

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Abstract

Bioretention gardens are used to help mitigate stormwater runoff in urban settings in an attempt to restore the hydrologic response of the developed land to a natural predevelopment response in which more water is infiltrated rather than routed directly to urban drainage networks. To better understand the performance of bioretention gardens in facilitating infiltration of stormwater in eastern Nebraska, the U.S. Geological Survey, in cooperation with the Douglas County Environmental Services and the Nebraska Environmental Trust, assessed the water balance of two bioretention gardens located in Omaha, Nebraska by monitoring the amount of stormwater entering and leaving the gardens. One garden is on the Douglas County Health Center campus, and the other garden is on the property of the Eastern Nebraska Office on Aging.

For the Douglas County Health Center, bioretention garden performance was evaluated on the basis of volume reduction by comparing total inflow volume to total outflow volume. The bioretention garden reduced inflow volumes from a minimum of 33 percent to 100 percent (a complete reduction in inflow volume) depending on the size of the event. Although variable, the percent reduction of the inflow volume tended to decrease with increasing total event rainfall. To assess how well the garden reduces stormwater peak inflow rates, peak inflows were plotted against peak outflows measured at the bioretention garden. Only 39 of the 255 events had any overflow, indicating 100 percent peak reduction in the other events. Of those 39 events having overflow, the mean peak reduction was 63 percent.

No overflow events were recorded at the bioretention garden at the Eastern Nebraska Office on Aging; therefore, data were not available for an event-based overflow analysis.Monitoring period summary of the water balance at both bio-retention gardens indicates that most of the stormwater in the bioretention gardens is stored in the subsurface.

Evapotranspiration was attributed to a small percentage of the outputs on an annual basis (3 percent at Douglas County Health Center site and 5 percent at Eastern Nebraska Office onAging site), which indicates that vegetative water uptake is not a primary factor in the water budget.

Suggested Citation

Strauch, K.R., Rus, D.L., Holm, K.E., 2016, Water balance monitoring for two bioretention gardens in Omaha, Nebraska, 2011–14, U.S. Geological Survey Scientific Investigation Report 2015–5188, 19 p., https://dx.doi.org/10.3133/sir20155188.

ISSN: 2328-0328 (online)

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Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Water Balance Monitoring
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Water balance monitoring for two bioretention gardens in Omaha, Nebraska, 2011–14
Series title Scientific Investigations Report
Series number 2015-5188
DOI 10.3133/sir20155188
Year Published 2016
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Nebraska Water Science Center
Description vi, 19 p.
Country United States
State Nebraska
County Douglas County
City Omaha
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Additional publication details