Lehigh Tannery Temperature Comparison of 2002 and 2005 Seasons
|This graphic shows a comparison of water temperatures recorded for the month of June at Tannery during the years of 2002 and 2005. Tannery is located approximately 6 miles below the FEW. In 2002 the Army Corps raised the lake elevation by 92 feet (1392 ft above sea level) above normal pool elevation for low flow augmentation to push back the salt line in the Delaware River at Trenton. In 2005, the Corps raised the lake by 35 feet (1335 ft above sea level) for recreational enhancement purposes.
Both years had similar weather conditions, HOT & DRY. The water temperatures for 2002 remained relatively cool. For most part below 20 Deg C (or 68 Deg F) as water was being discharged off the bottom of the lake. In 2005, water temperatures were typcially above 20 Deg C. In addition, water was being discharged at two locations in the lake water column. Water was being discharged through the bottom release gates and a set of by-pass gates located at elevation 1297 feet, approximately 45 feet off the bottom of the lake. On June 14, 2005 (see red circle area), the Lehigh River saw its first EVER designated coldwater release. For a period following June 14th, water temperatures remained relatively cool and below 20 Deg C.
What this shows us is that if greater quauntities of water can be stored in the reservoir a coldwater release is possible. The recent operation of the by-pass gates can now isolate the coldest water in the lake which may be retained until needed to reduce the water temps on the river. The Study that is required to be conducted by the Corps on FEW will investigate optimal uses of both the bottom release and by-pass gates and if there are any additional modificiations necessary in order to maintain the recommended release of water at 55 Deg F.