Water Resources Research Act Program

Details for Project ID 2017DC191B

Assessing the effectiveness of urban gardens in reducing stormwater pollution

Institute: District of Columbia
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $9,790 Total Non-Federal Funds: $19,675

Principal Investigators: Karen Knee

Abstract: The goal of this project is to better understand how urban gardens in Washington, DC, prevent runoff and reduce stormwater pollution. Urban gardens are increasing in popularity and are present in all of DC’s eight wards, often in public green spaces such as city parks, schoolyards and the U.S. Arboretum. Although many of the benefits and ecosystem services provided by urban gardens are well-documented, their ability to reduce runoff and stormwater pollution, especially in comparison to other types of vegetated urban land cover, has not been quantified. The proposed research will address that data gap by collecting field data from 9 planted beds in urban gardens, as well as 3 grassy plots and 3 green roof plots for comparison. A rainfall simulator will be used to simulate a heavy but realistic level of rainfall, and runoff collectors installed at each site will collect runoff from the plot during simulated and real rainfall events. Sampling with the rainfall simulator will be conducted monthly to observe how runoff quantity and quality varies over the course of the growing season and during fallow periods. Real rainfall events will be sampled as much as possible and compared to simulated rainfall events to assess how realistic the simulations are. During each sampling event, the quantity of real or simulated rain falling on the plot, the quantity of runoff generated, and in situ water quality parameters of the runoff (temperature, conductivity, and pH) will be measured and samples will be collected for later analysis of nutrient and dissolved metal concentrations at American University. An EasyChem plus discrete analyzer will be used to measure nutrient (nitrate+nitrite, phosphate, and ammonium) concentrations and an ICP-OES will be used to measure dissolved metal concentrations. This project builds upon research conducted by graduate student Anna Spiller, which resulted in the development of effective designs for the rainfall simulator and runoff collector as well as preliminary data suggesting that urban garden plots differ substantially from adjacent grassy plots in terms of the runoff they generate. It will provide support for a graduate student at American University. I also anticipate, based on strong student interest in urban agriculture and sustainability, that one or more undergraduate students will work on the project as volunteers or for academic credit. This project will quantify the hydrological ecosystem services provided by urban gardens and to compare them directly to other types of green space or green infrastructure commonly found in the urban environment. The data generated will help agencies such as DC Water, District Department of the Environment and the Department of Parks and Recreation make informed decisions about how urban gardens can be part of the District’s overall stormwater management plan, thus promoting better stormwater management and leading to improved water quality in local rivers and streams. The results will also be broadly applicable to other cities with similar climate and rainfall where urban gardens are present.