The Allegheny in New York, at Print Size
Every river, creek and run in the corner of New York whose water ends up in the Gulf of Mexico, drawn long enough to hang over a doorway. Free, at full resolution.
10,800 × 4,500 pixels at 300 DPI, which is 36 × 15 inches on paper: a panorama, because the watershed is one. It is 125 miles wide and 40 miles deep, and no other shape would fit it without wasting half the sheet.
| Tributary system | Square miles | Miles of stream | Lakes & ponds | Miles to the Gulf |
|---|---|---|---|---|
| The Allegheny itself | 506 | 1,069 | 653 | 2,218 |
| Conewango Creek | 416 | 737 | 1,975 | 2,197 |
| Chautauqua Lake & the Cassadaga | 350 | 516 | 1,626 | 2,200 |
| Ischua & Olean Creeks | 207 | 422 | 427 | 2,233 |
| Great Valley Creek | 140 | 334 | 205 | 2,200 |
| French Creek | 112 | 217 | 111 | 2,180 |
| Oswayo Creek | 90 | 160 | 70 | 2,229 |
| Brokenstraw Creek | 72 | 127 | 26 | 2,170 |
| Tunungwant Creek | 34 | 71 | 15 | 2,194 |
| All of it | 1,926 | 3,652 | 5,108 | 2,233 |
Why this corner and no other
New York drains four ways. Most of it goes to the Atlantic down the Hudson, the Delaware, or the Susquehanna to the Chesapeake; a great deal more goes out through the Great Lakes and the St. Lawrence. Only here, in Chautauqua, Cattaraugus and Allegany counties, does it go the other way: down the Allegheny to the Ohio, the Ohio to the Mississippi, and the Mississippi to the Gulf of Mexico. This sheet is the whole of it, 1,926 square miles against the 1,927 New York State publishes.
The edge is two different kinds of line
The boundary of this watershed runs 315 miles. 212 of them are a drainage divide, where rain landing on one side of the line ends in the Gulf of Mexico and rain landing on the other ends in the Atlantic. The remaining 103 miles are the 42nd parallel, surveyed in 1787, where rain landing on either side ends in precisely the same place. The sheet draws the first in gold and the second as a grey dash, because they are not the same kind of fact and a map about where water goes should not pretend they are.
The divide was then walked at four-hundred-metre intervals and asked, at every step, what lay on the far side of it. 156 miles answer Lake Erie and 57 the Genesee, and so Lake Ontario. Not one mile of it faces the Chesapeake: the Genesee gets between them. Every step of this line is the same choice between the Gulf of Mexico and the St. Lawrence.
Water leaves New York here in 69 places
It does not leave down one river. Every reach whose upstream end is in New York and whose downstream end is not was counted, and there are 69 of them, 23 carrying a name: the Allegheny itself, the Conewango, French Creek, Brokenstraw, Little Genesee Creek and eighteen more. Pennsylvania water crosses back the other way at 51, including the Allegheny, the Tunungwant running north out of Bradford, and Oswayo Creek, which leaves New York and comes back.
How far it is to the sea
Every reach was walked down its own river to the end of the survey, at the Point in Pittsburgh. The furthest point from salt water in New York State turns out to be the head of Ischua Creek, above Machias: 298 river miles to Pittsburgh, then the Ohio's 981 to Cairo and the Mississippi's 954 to the Gulf. 2,233 miles. The same walk gives the Allegheny River itself 328 miles against the 325 it is published at, which is the check that says the walk is right.
What it is drawn from
The divide and the nine tributary systems are the USGS Watershed Boundary Dataset: the seventeen HUC10 watersheds of the Allegheny subregion that reach New York, unioned and cut to the state. The water is the USGS National Hydrography Dataset at high resolution. NHD ships an arbolate sum and a stream order for this subregion and both are null in all 57,859 rows of them, so the network was rebuilt by snapping every reach end to end and accumulating length downhill; that number is what sets how wide each stream is drawn. The accumulation runs over the whole Allegheny basin and not just the New York part, because the river crosses the line at Portville already carrying 1,288 miles of Pennsylvania stream and a sheet that started counting at the border would draw it as a creek. The state line is US Census TIGER.
The reservoir at the bottom
Kinzua Dam was finished in 1965. The reservoir behind it flooded 10,000 acres of the Seneca Nation's Allegany Territory and nine of its communities, and forced the relocation of some 600 people, against the Treaty of Canandaigua of 1794. It is the largest body of water on this sheet and it is worth knowing what it is.
Printing it
It is a lot of dark ink. A matte or lustre paper holds the fine streams better than glossy, and any shop that takes a 300 DPI JPEG can run it at 36 by 15. Smaller is fine too: at 18 by 7.5 it is 600 DPI and every headwater is still there.
Free to print and hang, yours or a gift. If you sell it, that is not free. ☕ Coffee if it ends up on your wall.
There are sheets of all five Great Lakes basins and of Lake Ontario alone drawn the same way, on the other side of the divide at the top of this one.