Barnes Brook begins atop Bartlett Mountain in North Branch Township, Wyoming County. It flows west-southwest for a few tenths of a mile before turning northwest and beginning to quickly descend the mountain into a deep valley. After several tenths of a mile, the stream enters Colley Township, Sullivan County and receives its only named tributary, Coffee Brook, from the. The stream then turns north for several tenths of a mile before turning north-northwest for a few tenths of a mile. It then exits the valley and reaches its confluence with North Branch Mehoopany Creek. Barnes Brook joins North Branch Mehoopany Creek upstream of its mouth.
Tributaries
Barnes Brook has one named tributary, which is known as Coffee Brook. Coffee Brook joins Barnes Brook upstream of its mouth and drains an area of.
Hydrology, geography, and geology
The elevation near the mouth of Barnes Brook is above sea level. The elevation near the stream's source is above sea level. Barnes Brook is a high-gradient stream, falling at a rate of. This is the second-highest gradient of any named direct tributary of North Branch Mehoopany Creek, after Catlin Brook. It flows in a generally northwesterly direction. Mountains in the watershed of the stream include Bartlett Mountain and Briskey Mountain, the latter of which is where its headwaters are. In an August 2001 study by the Pennsylvania Fish and Boat Commission, Barnes Brook was found to be entirely dry, except for a number of stagnant pools. When the ambient air temperature was, the water temperature at the stream's mouth was found to be. The pH of the stream at its mouth was 6.6 and the alkalinity was. The water hardness was and the specific conductance was 111 umhos.
Watershed and biology
The watershed of Barnes Brook has an area of. The stream is entirely within the United States Geological Survey quadrangle of Jenningsville. It joins North Branch Mehoopany Creek near Lovelton. Only 4 percent of the length of Barnes Brook is within of a road. However, 51 percent is within of a road and 64 percent is within of one. In 2000, the population density of the stream's watershed was 4 people per square mile. Most of the watershed is forested land and part of it is in Pennsylvania State Game Lands Number 57. Barnes Brook is classified as a Coldwater Fishery. In 2001, the stream was found to lack fish habitats. However, the Pennsylvania Fish and Boat Commission will hold a meeting in January 2018 to consider adding the entire length of the stream, along with many other streams, to its list of wild trout streams.
