Credit: Dave Burbank PhotographyCredit: Dave Burbank PhotographyCredit: Dave Burbank PhotographyCredit: Dave Burbank Photography

Watershed Information

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What is a watershed?

A watershed is a geographical area where water drains into a particular stream or lake. In addition to the geologic setting are the biological and physical characteristics of a watershed, which determine how water flows across the land and underground until it reaches a stream, lake, or ocean. A healthy watershed is vital for a healthy environment and economy. 

Six Mile Creek Watershed

Six Mile Creek WatershedDrinking water in the City of Ithaca comes from the Six Mile Creek watershed, which extends southeasterly from the city about 20 miles and covers an area of approximately 46.5 square miles. The City of Ithaca has been working to manage the Six Mile Creek watershed for drinking water for over 100 years. 

A Piece of Six Mile Creek History

The last glaciation covered this region with ice, concentrating water flow into valleys, including that of Six Mile Creek. The glacial retreat left a deeper Cayuga Valley, and in some areas streams cut into bedrock, forming gorges. Throughout the 19th century, agricultural practices of land clearing eroded soil and increased the sediment load of Six Mile Creek. After groundwater sources were not enough to meet the needs of the growing Ithaca population, three reservoirs were created on Six Mile Creek between 1892 and 1911. These reservoirs dammed the post-glacial gorges along the stream. The first reservoir was a mill dam at Van Nattas (currently Giles St. stream crossing) purchased by the Ithaca Light and Water Company to bolster water sources. More upstream sources were required as demand grew, and in 1902 the 30 foot dam was built upstream of Van Nattas in a second gorge. Finally, to acquire more storage and reduce the cost of pumping water, the 60 foot dam (Potters Fall Reservoir) was constructed in 1911. Sediment began to fill the 60 foot dam, and by 1925 the smaller Silt Dam was constructed as a pre-settling basin. 

Present-Day Six Mile Creek

Today, the reservoirs continue to operate as designed, utilizing the gorges and gravity for water storage and delivery. However, the erosion rates and sediment load of Six Mile Creek continue to remain high despite more recent reforestation of the area. Current and future land management strategies will continue to take into account the local history and geology to reach a balance between present day land use, erosion rates, and drinking water needs. 

For more information about the Six Mile Creek watershed, view:


Cayuga Lake Watershed

The Six Mile Creek Watershed is a subwatershed of a larger network, the Cayuga Lake Watershed. Other major subwatersheds in Ithaca include Fall Creek, Cascadilla Creek, and Cayuga Inlet (see map on left). 

The Cayuga Lake watershed is the largest of the Finger Lakes, spanning 785 square miles of agricultural, industrial, residential, and forested land. The lake is fed by a network of 140 streams, and its watershed is home to over 120,000 people. Cayuga Lake is also the longest (38.2 miles long), widest (1.75 miles wide), and one of the deepest (435 feet deep) of the Finger Lakes. Because of Cayuga Lake's size and depth, water that enters the lake takes over a decade to cycle through the lake. 

Local partners, including but not limited to the Cayuga Lake Watershed Network and Cayuga Lake Watershed Intermunicipal Organization, help maintain and protect this essential water source.

For more information about the Cayuga Lake watershed, view: 


Keeping Our Watershed Safe 

The mission of the City of Ithaca Water & Sewer Division is to enhance the health and quality of life in the Ithaca Community by providing an adequate supply of safe water and to treat and dispose of the City's wastewater in a responsible manner. In keeping with this mission, the environmental integrity of the watershed is one of our major responsibilities. 

However, the public also plays an important role in maintaining the health of our watershed. Do your part in keeping our watershed safe by avoiding these common sources of pollution that harm our waterways. 

Sources that pollute the watershed: 
  • Littering
  • Improperly maintained septic tanks
  • Increase in paved areas
  • Improper use of lawn, crop and garden chemicals
  • Destruction of wetlands
  • Channelized and concrete-lined drainage ways
  • Oil, antifreeze, and gas leaks from autos
  • Improper containment and disposal of animal waste
  • Stream bank/road bank erosion
  • Agricultural, urban, and storm water run-off


Learn what you can do to help promote a healthy watershed through these tips from the Environmental Protection Agency (EPA).