Hydrologic and Hydraulic Monitoring

Long-term records of stream and sewer system flow information are essential for seeing results of our stormwater management and watershed restoration initiatives.

Water level sensor installed in brick sewer (left), USGS hydrologist calibrates stream flow gage (center), USGS stream gage wireless transmitter (right)


PWD requires a large amount of hydrologic and hydraulic data for sewer system operation, design, and planning, in addition to watershed monitoring. PWD monitoring resources include a network of 24 rain gages, 11 USGS stream gaging stations, as well as a number of permanent and temporary in-system flow monitoring systems. Many of these systems provide data in real time or within hours.

PWD Rain Gage Network

PWD operates a network of 24 tipping-bucket type rain gages in the City of Philadelphia, providing rainfall data accurate to 0.01 inch at 2.5-minute intervals. Most of these gages are located on PWD or other City-owned facilities, distributed throughout the City to provide even coverage as much as possible. PWD rain gage information is presently only available to the public via the web in the CSOcast web application, but we are developing alternate electronic data delivery mechanisms and data are available upon request.

For long-term trends, such as storm event recurrence intervals, PWD relies on data collected from Philadelphia International Airport, a station with more than 100 years of meterological data.

USGS Stream Gaging Stations

PWD partners with the USGS to provide near real-time water quality and streamflow data at 11 stream gaging stations in Philadelphia's watersheds. USGS maintains streamflow monitoring equipment, while PWD staff are responsible for maintaining water quality instrumentation.
Philadelphia Water Resources Monitoring Program Website

In-System Flow Monitoring

PWD collects flow data at several locations throughout the stormwater and wastewater networks, utilizing permanent and temporary monitoring equipment. This flow information is presently used primarily for modeling purposes to plan and analyze alternatives for improvements to the sewer system. However, in the future these data will be used, along with other types of monitoring, to evaluate the success of stormwater management and watershed restoration initiatives. For example, the impact of small-scale green infrastructure projects that affect only a few City blocks or a few acres of impervious cover will generally be easier to detect within a small sewer catchment rather than at USGS stream gaging stations with relatively very large drainage areas.