Reservoir Flows Advisory Committee
The purpose of the Reservoir Flows Advisory Committee (RFAC) is to make recommendations to the Delaware River Basin Council (DRBC) for flows regimes regarding the three NYC DEP reservoirs of the Upper Delaware system. Glenn Erikson of the WTF regularly attends these meetings. WTF has evolved into becoming a primary voice for East Branch of the Delaware River fishery in these hearings. We believe that the most important current matters before the RFAC regarding flows from all three reservoirs revolve around high water temperature events and maintaining a maximum of 75 degrees at Lordville. Regarding the East Branch we feel the most important issues are: 1) the annual amount of water flowing out of Pepacton Reservoir be no less than that of Revision 7 of the operating plan, and/or a summer flow of 225 cfs at Harvard, and 2) late summer/early fall flows be maintained at a significantly higher level than the current FFMP, primarily to insure that late summer heat waves do not overly increase water temperatures. We also believe that more research needs to be done regarding the health of the fishery in relation to anchor ice (which can kill juvenile trout wintering in crevices near shore), frazil ice (ie ice in the water column that can become caught in a trout’s gills causing death), and Didymo (which often blooms and thus displaces algae food sources for juvenile trout and aquatic insects).
Delaware Watershed Conservation Coalition (DWCC). WTF is a founding member of the DWCC, which is led by Dan Plummer of the Friends of the Upper Delaware River (FUDR), and includes as its members such fly fishing conservations organizations as Theodore Gordon Flyfishers (TGF) and Trout Unlimited (TU), as well as other conservation organizations such as the
Water Temperatures. Subsequent to the construction of the Pepacton Reservoir the NYC Department of Environmental Preservation (NYC DEP) has operated its releases from under what are known as the original operating agreement and Revisions 1 through 7. This operating agreement is between the NYC DEP, the NYS Department of Environmental Conservation (NYS DEC) and the Delaware River Basin Commission (DRBC). Under the flow regimes established by Revision 7 the summer high water temperatures recorded at the Harvard USGS gauge never exceeded 70 degrees---except when the Pepacton Reservoir releases were operating under drought conditions and thus at much lower flow levels. Since the adoption of the Flexible Flow Management Policy (FFMP) in 2007, the summer high water temperatures have exceeded 70 degrees five times. On an annual basis, they have exceeded 70 degrees three years out of four. Temperatures above 70 degrees are harmful to trout and are a limiting factor to the sustainability, let alone the growth, of the fishery. Temperatures above 75 degrees are lethal to trout. One of the goals of the WTF is to effectuate a change in the FFMP for the Pepacton Reservoir so that these summer water releases are higher, and thus provide the lower temperatures required for the sustainability of this fishery. In addition, as there is an inverse relationship between water temperature and levels of dissolved oxygen, increasing dissolved oxygen will to some extent mitigate for higher water temperatures.
Dissolved Oxygen Levels. Both the reduced water flows and higher water temperatures noted above also effect the levels of dissolved oxygen in stream waters. Dissolved oxygen is extremely important to trout as this is the oxygen their gills extract from the water for them to live. As water temperatures increase, the physiology of trout is such that the amount of dissolved oxygen must increase or they will be under greater stress. At 70 degrees this becomes critical. However, the East Branch of the Delaware is a relatively low gradient trout stream, with an average gradient of only 0.05% from the Route 206 bridge to the Route 17 bridge, a total of 15 miles. Thus there are no rapids and relatively few “white water” riffles to replace the oxygen that naturally dissipates from the water as it travels downstream. Thus, given the lower FFMP water releases that have increased the temperatures in the East Branch, we believe that dissolved oxygen is now a potential limiting factor at Long Flat, and certainly must be in the lower sections of the river.
Food Biomass. The lower water flows resulting from FFMP will necessarily reduce available food biomass to trout due to the direct relationship between the two. Unfortunately, this reduction in water occurs in the late summer and fall, just when trout need to bulk up for the winter. However, we believe that for available food biomass to be a limiting factor in adult trout biomass, all other more limiting factors must first be resolved. For example, if there is insufficient winter yearling cover resulting in a high die off of yearlings, then an increase in available food biomass will have little or no impact on observed adult trout biomass. However, once more limiting factors have been favorably resolved, then adding available food biomass for adult trout we believe would increase their biomass.