They had been releasing water at a fairly high rate quite consistently for some time this past mid spring into mid summer via the S. Br. Rockaway Crk. This creek had its headwaters cut off when the res was built so a release mechanism was designed into the dam to allow for a maintenance flow to maintain an established baseline flow in the creek. In addition they often use this outlet in conjunction with or as an alternate to the pumping station on the S. Br. Raritan to help maintain the required baseline flow in the mainstem Raritan.
I don't know why they lowered the res as they have, although I do have an idea or 2, but if you check this USGS guage you can see the extent and volume of the releases...
http://waterdata.usgs.gov/nj/nwis/uv...65,00060,62614 You'll see they finally shut off the flow most recently on July 28. My first guess as to the 'why' would be an intent to pump some 'fresh' more nutrient-bearing water from the SBR into the res at some point in an attempt to boost the food chain from the bottom up since this has been an on-going problem there. Then again it may just be a need to do some maintenance work on some structures there.
BTW, the water isn't pumped from Spruce Run Res, it's pumped directly from the SBR just above the YMCA Camp Carr. They have the ability to both pump up to the res from here as well as release water back into the SBR, which they often do during the summer to maintain the Raritan mainstem flow level. An alternative release into the SBR from RVR would be via Prescott Brk which also had its headwaters cut off by the res and as such has a release built into the dam on the SW side of the res to maintain the brooks flow. However this outlet is generally never used for this purpose, just as a maintenance flow for the brook.
