Drinking 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.