FORM AND FUNCTION: COMPARING TWO CONSTRUCTED WETLANDS AT BINGHAMTON UNIVERSITY

Impervious surfaces in urban areas have created a need for stormwater management practices to mitigate runoff quality and quantity concerns. Artificial wetlands are one of these practices, and Binghamton University has two constructed wetlands on campus, Bartle Wetlands (BW) and Lake Lieberman (LL), each with differing sizes and shapes. These wetlands are designed to improve the quality and lessen the amount of runoff flowing into downstream areas. Both capture runoff from closely sized catchments with similar percentages of impervious surfaces (36%). BW consists of multiple pools connected to each other (1000m² in total surface area), and three vertically stacked 8cm diameter PVC pipes at the exit to allow stormwater discharge. LL consists of a single large pool with a 2m weir at the exit, and a permanent pool surface area of about 4,000m².

The overall goal of our work is to provide a quantitative comparison between the two systems, and to determine which is better at stormwater attenuation. This required the use of physical and chemical mass balance calculations, with sensors providing continuous water quality and quantity measurements. Collection of water samples and rain gauge data were used to supplement the sensor data.

We will present information to: 1) demonstrate how sensor placements were optimized to reveal the dilution and mixing that occurs in the wetlands after road salting and rainfall events, 2) determine volumetrically how much water enters and leaves the retention ponds during and after rain events, 3) compare the water retention time of each site in relation to size and intensity of rainfall, 4) compare the baseline conductivities of runoff at both sites during different seasons to determine how long saline water is retained in soil or groundwater, and 5) determine residence time of road salt within constructed wetlands after winter salting events.

A major finding was that the smaller exit at BW results in a longer retention time of both stormwater and road salt. However, it was found that LL has more groundwater input, which assists in diluting legacy and recent road salt additions to stormwater prior to exiting this system. Quantitative analysis of the form and function of the constructed wetlands on campus is translatable for improving future green infrastructure in many urban areas.