Editing Canal pound (section)

====Water supply====
[[File:Patowmack_canal_used_as_feeder_to_C_and_O_Canal.jpg|right|thumb|200px|A feeder canal to feed the Georgetown level of the Chesapeake and Ohio Canal.]]
One main concern to the engineer was the canal's water supply. Pumping would contribute greatly to operating expense, especially at the summit level, hence gravity fed water is preferred. Feeder canals could be {{convert|20|mi|-1}} to {{convert|30|mi|-1}} in length, if needed.<ref name="Oldtowpaths303">Old Towpaths, 303</ref> The canal bed would have to slope so that the water would not flow too fast down the canal and impede the progress of upstream boats.<ref name="Oldtowpaths303"/>

Rivers were often dammed to raise the water's height so that the canal could be fed, for instance, the Chesapeake and Ohio canal had seven dams built to feed water.<ref>Unrau, Historical Resource Survey, p. 241-242</ref>

If a dam was not built, often water had to be pumped. The Chesapeake and Ohio put a steam pump near the South Branch, near mile 174, which had a capacity of about {{cvt|25|cuft/s|m3/s}}, since the water from Dam No. 8 was insufficient.<ref>Hahn, Thomas. Towpath Guilde</ref><ref>{{cite web|url=http://www.nps.gov/history/history/online_books/choh/unrau_hrs.pdf|title=Historical Resource Study: Chesapeake & Ohio Canal|author=Unrau, Harland D.|publisher=[US Department of the Interior, National Park Service]|access-date=2013-05-02}}, p. 470</ref> This problem is particularly acute on summit pounds (see below).

On the [[Pennsylvania Canal (Delaware Division)|Delaware Division]] canal, the Delaware River was made to pump its own water into the canal, using an undershot water wheel which was connected to another wheel which had buckets attached, thereby lifting the river water up to the canal.<ref>Old Towpaths, p. 306</ref>