Glen Brook is a tributary of East Branch Briar Creek in Luzerne County and Columbia County, in Pennsylvania, in the United States. It is approximately long and flows through Salem Township in Luzerne County and Briar Creek Township and Berwick in Columbia County. Its watershed has an area of . A number of dams and reservoirs have been built on the creek and two major bridges cross it. The stream lies over mudstone, siltstone, limestone, sandstone, and shale. Glen Brook is slightly alkaline, with a median pH of 7.37. The median water temperature of the stream is . It is inhabited by trout and is considered to be Class A Wild Trout Waters. Course Glen Brook begins on the southern side of Lee Mountain in Salem Township, Luzerne County. It flows east-southeast for a short distance before turning southwest and flowing into a valley. After approximately a mile, it enters Briar Creek Township, Columbia County and receives an unnamed tributary. It then turns south-southeast for several tenths of a mile, passing the Glen Brook Number Four Dam. Near the border between Columbia County and Luzerne County, the stream turns southwest and flows into Foundryville, where it makes a sharp turn east and then west, entering Berwick. In Berwick, it turns west-northwest and then southwest, roughly following the northern border of the borough. After several tenths of a mile, the stream leaves Berwick and returns to Briar Creek Township. A short distance later, it reaches its confluence with East Branch Briar Creek. Glen Brook joins East Branch Briar Creek upstream of its mouth. Hydrology The discharge of Glen Brook ranges from 0.58 to 60.2 cubic feet per second. The median discharge is 4.915 cubic feet per second. The water temperature of the stream ranges from to . The median water temperature is . The electric conductance of the stream's waters ranges from 68 to 266 milli-siemens, with a median of 96 milli-siemens. The minimum pH of Glen Brook is 7.06 and the median pH is 7.37. The maximum pH is 7.79. The concentration of total dissolved solids in the stream ranges from 35 to 145 parts per million, with a median of 49 parts per million. The concentration of alkalinity in the waters of the stream is 16 milligrams per liter. In a visual assessment by the Briar Creek Association for Watershed Solutions, Cabin Run was given a score of 7.0