USGS Nebraska Water Science Center

Monitoring the Effectiveness of Bioretention Cells

Eastern Nebraska Office on Aging

Bioretention Cell Design

The Eastern Nebraska Office on Aging (ENOA) bioretention cell is located in the central part of Omaha, Nebr., on the southwest corner of the intersection of 42nd and Center Streets. The ENOA bioretention cell initially had a drainage area of about 0.48 acre; however, after the initial 2 years of monitoring (2011–12), modifications were made at the bioretention garden that increased the drainage area to 0.78 acre and increased the size of the parking lot drainage gates.

The drainage area is almost completely impervious and consists of a part of the ENOA building’s rooftop, surrounding parking lot, and an area of greenspace to the southeast of the building. The runoff flow for the parking lot is collected into three lateral parking lot drain grates and is then routed by pipe to the bioretention garden inflow channel. Once the cell has reached capacity, overflows are routed through a valved pipe to the combined sewer.


Water Balance

The water balance of this cell is measured using

  • precipitation,
  • surface inflow,
  • outflow through the infiltration trench,
  • outflow through the overflow,
  • evapotranspiration, and
  • the change in stored runoff.

The remaining component of the water balance, infiltration, is being estimated as the residual of the water balance.

All of the components of the water balance were measured every 15 minutes during nonflow periods; however, inflow, outflow from the standpipe, and amount of ponded water were measured every minute when flow was measureable or when water depths were higher than 0.03 ft in each sensor (ponding). Collected data were stored using electronic data loggers and transmitted in near real time to the USGS National Water Information System Web site (NWISWeb).

Available Data

Data are available through the USGS NWISweb: ENOA DATA

Annual water balance components for all events, 2011–14.