WHAT IS HAPPENING AT PISB?
The rain garden at the Papadakis Integrated Sciences Building (PISB) receives stormwater runoff from the building’s rooftop and surrounding area, allowing the runoff to infiltrate slowly into the ground instead of quickly entering and overwhelming the sewer system when it rains.
This site consists of two rain gardens (drainage areas = 9,850 and 19,000 ft2, respectively) with underground rock bed and vegetated soil top. Rainwater collected from the roof of PISB and the nearby permeable paved sidewalk is directed into the garden. The rainwater either evaporates, is used by plants through transpiration, or slowly infiltrates into the soil. In the event of a heavy rainfall, rainwater will go into an overflow which directly leads to the combined sewer system.
The goal of the research is to use a variety of sensors to investigate how soil moisture is related to the ways that precipitation enters, exits, and is stored in rain gardens. The experiment tests low-cost environmental monitoring equipment for its ability to transmit and store data.
Ultimately, this experiment will help us learn more about how microclimate conditions and maintenance irrigation impact the soil moisture and plant health.
WHAT IS A RAIN GARDEN?
A rain garden receives stormwater generated on surrounding surfaces, helping to infiltrate it into the soil. Rain gardens can take on water from a roof, patio or yard, and are also being installed in sidewalks to capture runoff water generated from the street. Rain gardens are a type of Green Stormwater Infrastructure (GSI) being installed throughout Philadelphia to improve water quality in the Schuylkill and Delaware Rivers and their tributaries.
Rain gardens are one of the simplest and most effective ways to reduce stormwater pollution, while providing extra benefits such as beautifying the urban landscape and creating habitat for pollinators!
HOW DO WE COLLECT DATA?
Sensors measure the soil moisture in the rain garden. The sensor is connected to a microcontroller that transmits the data to a database.
Data is transmitted over a LoRa (Long Range) Network
WHAT DOES THE DATA LOOK LIKE?
The graph below shows the soil moisture responses in different parts of the rain garden: the east bank (orange), the west bank (purple) and the bottom (green).
Real-time soil moisture monitoring at PISB:
The site’s soil moisture is measured in three locations with two Particle Electron boards connected to Decagon EC-5 and 10-HS sensors. They report the soil moisture every seven minutes and store it in our Amazon Web Services database as well as on Thingspeak (an open-source Internet of Things application and API to store and retrieve data).
Real-time soil moisture data at the PISB rain gardens is shown in the below figures:
Real-time soil moisture data from PISB 1:
Real-time soil moisture data from PISB 2:
WHAT HAVE WE LEARNED SO FAR?
PISB is one of many gardens being monitored as part of this project. The custom-built, low-cost IoT (Internet of Things) monitoring setup performs well, and has been extended to monitor soil moisture at multiple rain garden sites across the city. Significant differences in soil moisture were observed between the bank and the low point of the monitored rain gardens.
This experiment is ongoing! Future research will model water content in the soil during dry spells and validate the model against data collected in the network to investigate if the need for irrigation can be predicted remotely.