The soil moisture in a GSI subsurface system increases or decreases over time as water enters the system or as it moves deep down to the underlying surface or to the sewer system, respectively. The variation of these soil moisture conditions needs to be addressed as it allows us to understand how the water dynamics within the soil column is defining the flow condition. For understanding the water availability in subsurface layer in a GSI system, the soil moisture behavior is studied for a GSI unit in Philadelphia where soil moisture sensors are installed at 10 cm, 35 cm and 60 cm soil depth at two horizontal locations. The soil moisture measurement for the selected GSI unit at these distinct depths is studied for specific rainfall events, to provide a conceptual framework of quantitatively understanding the soil moisture behavior for different water availability scenarios in pre-, during and post-storm conditions. Soil moisture sensors respond to the input of stormwater into the soil. As the void spaces in the soil is filled with water, the permittivity of the surrounding soil material increases followed by an increase in volumetric moisture content and decreases as water is infiltrated deep into the soil. The soil moisture trends are identified to interpret the soil moisture content over time, which can indicate the impact on runoff generation, plant growth or soil erosion. Preliminary results indicate that while there is variability, overall, there is a consistent trend in behavior. This field scale measurement of soil moisture provides the detail of the field variability in the GSI system, and the overall trends demonstrate broader knowledge of subsurface GSI dynamics.

Access the Conference Proceedings Paper on ASCE Library

The soil moisture in a GSI subsurface system increases or decreases over time as water enters the system or as it moves deep down to the underlying surface or to the sewer system, respectively. The variation of these soil moisture conditions needs to be addressed as it allows us to understand how the water dynamics within the soil column is defining the flow condition. For understanding the water availability in subsurface layer in a GSI system, the soil moisture behavior is studied for a GSI unit in Philadelphia where soil moisture sensors are installed at 10 cm, 35 cm and 60 cm soil depth at two horizontal locations. The soil moisture measurement for the selected GSI unit at these distinct depths is studied for specific rainfall events, to provide a conceptual framework of quantitatively understanding the soil moisture behavior for different water availability scenarios in pre-, during and post-storm conditions. Soil moisture sensors respond to the input of stormwater into the soil. As the void spaces in the soil is filled with water, the permittivity of the surrounding soil material increases followed by an increase in volumetric moisture content and decreases as water is infiltrated deep into the soil. The soil moisture trends are identified to interpret the soil moisture content over time, which can indicate the impact on runoff generation, plant growth or soil erosion. Preliminary results indicate that while there is variability, overall, there is a consistent trend in behavior. This field scale measurement of soil moisture provides the detail of the field variability in the GSI system, and the overall trends demonstrate broader knowledge of subsurface GSI dynamics.

**[Access the Conference Proceedings Paper on ASCE Library](https://doi.org/10.1061/9780784481783.017)**

Subsurface Monitoring of a GSI System using Soil Moisture - A Philadelphia Case Study

Created in 1999, the Environmental & Water Resources Institute (EWRI) is the recognized leader within ASCE for the integration of technical expertise and public policy in the planning, design, construction, and operation of environmentally sound and sustainable infrastructure impacting air, land and water resources.

[Paper Proceedings](https://doi.org/10.1061/9780784483466)

Conference DOI: https://doi.org/10.26226/m.6329c39b68fb0e00131f77d2