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Regional & Global Trends

Numerous environmental, social and developmental trends materializing in Philadelphia's watersheds raise concern for the future health of our waterways.

Climate Change

Climate change is a change in the statistical distribution of weather over periods of time, ranging from decades to millions of years. In the northeastern U.S., increased overall precipitation and changes in vegetation could exacerbate bank scouring and lead to more pollutants washing into our waterways. Climate change can be detected through the examination of various indicators.

Sea Levels

As sea levels rise, the salt line from the Atlantic Ocean creeps further upstream into the fresh water of the Delaware River. The Water Department has intakes on the Delaware River that supply drinking water to the city. If the water level rises enough for salt water to reach these inlets, it could inundate our infrastructure and have a large impact on our drinking water. The current drinking water treatment process is not designed to remove salt. As rising sea levels and an encroaching salt line become legitimate threats, we would have to re-engineer our treatment plants or move the inlets farther upstream — either of which would carry a significant cost.

Surface Temperature

Studying historical trends and comparatively monitoring current data help us draw conclusions about future surface temperature changes. Increased surface temperatures naturally raise the temperature of water bodies. As water becomes warmer, bacteria growth proliferates, choking the oxygen supply for aquatic life.

Severe Weather Conditions

As surface temperatures climb, so will the frequency of short-term droughts and intense storms. These weather extremes can affect our drinking water quality and quantity, inhibit the ability of aquatic life to survive, and cause massive flooding - ultimately increasing CSO overflows into our waterways. More severe weather could compromise facilities and lead to more frequent spills and accidents.

Land Change

When land is altered from its natural state, the hydrology cycle is interrupted. This is primarily a concern for the Schuylkill and Delaware watersheds, which are very large and where development occurs far upstream of Philadelphia.


One form of land change results from development and construction. As housing and street networks expand to accommodate growing populations, more impervious cover is created, which exacerbates stormwater runoff and non-point source pollution. The availability of water becomes a legitimate concern as development and sprawl consume more land and natural resources.

Population Change

As populations increase or decrease, the environment consequently undergoes changes.

Population size impacts the carrying capacity that a given environment can sustain over the long term. Food, water, living space, environmental conditions, and sanitation infrastructure are all variables necessary to survival, and their availability largely relies on the demand of all biological populations.