Cannonsville Reservoir Research Articles

Chemical Exchange at the Sediment-Water Interface of Cannonsville Reservoir

ABSTRACT Rates of chemical exchange at the sediment-water interface of Cannonsville Reservoir were determined using intact sediment cores. Reference sites for coring were selected based on the results of a surficial sediment survey. Higher levels of volatile suspended solids, chemical oxygen demand, total organic carbon, total nitrogen, and total phosphorus were noted at deep water stations proximate to the dam and near the discharge of the West Branch of the Delaware River (WBDR, the reservoir's major tributary). Rates of sediment oxygen demand (SOD), measured at 20 °C at the three reference sites, ranged from 0.66 to 1.67 gO2 · m−2 · d−1 with a mean±s.d. of 1.06±0.23 gO2 · m−2 · d−1. No statistically significant variation in SOD with location in the reservoir was noted. No phosphorus (P) release was detected under aerobic conditions. Rates for cores incubated under anaerobic conditions ranged from 9.2 to 15.6 mgP · m · −2 · d−1, with a reservoir-wide mean±s.d. of 12.9 ± 2.2 mgP · m−2 · d−1. P-release rates at P-enriched sites (surficial sediment survey) were higher than at mid-reservoir locations with lower sediment-P. Rates of ammonia-nitrogen (NH3−N) release ranged from 19.6 to 43.2 mgNH3−N · m−2 · d−1 with a reservoir-wide mean ± s.d. of 31.8 ± 7.2 mgNH3−N · m−2 · d−1. A general trend of decreasing sediment NH3−N release with distance from the discharge of the WBDR was noted. Rates of sediment exchange measured here are consistent with those reported for other systems of a similar degree of nutrient enrichment and trophic state. Downcore profiles of sediment chemistry suggest that while organic carbon and nitrogen are undergoing diagenesis in the reservoir (SOD is exerted and NH3−N release is observed), P deposited to the sediment remains in the particulate form and is not recycled. The sediments are, however, rich in the forms of particulate P which support release. High rates of P exchange maybe expected if trophic state conditions deteriorate further, resulting in extended anoxia.

Characteristics and Origins of Metalimnetic Dissolved Oxygen Minima in a Eutrophic Reservoir

ABSTRACT The occurrence and characteristics of metalimnetic dissolved oxygen (DO) minima are documented, the origins of the phenomena are evaluated, and the contribution of DO consumption in this layer to overall consumption below the epilimnion is resolved, for Cannonsville Reservoir, NY. The analysis utilizes detailed vertical profiles of temperature and DO collected in the lacustrine zone of the reservoir over the 1988–1997 interval, profiles of scalar irradiance and fluorescence measured in 1995, calculations of vertical profiles of phytoplankton production and respiration of DO for selected conditions, and mass balance analyses for DO in the metalimnion and hypolimnion of the reservoir over the 10-year record. The metalimnetic minimum is shown to be a recurring phenomenon in the reservoir, that was conspicuously manifested in late summer in each of the 10 years. The position of the minimum below the water surface has been rather uniform in mid-summer but other features, including the extent of DO depletion, have varied greatly. Respiration of relatively high concentrations of phytoplankton biomass within the metalimnion, located below the compensation depth, contributed to the development of the observed minima. The high phytoplankton concentrations of the metalimnion probably are associated with slowed descent rather than interflow(s). On average, ~ 70% of the DO consumption exerted below the epilimnion over the 1988–1997 interval occurred in the metalimnion. The average DO consumption rate in this layer, normalized for layer volume, was 80 mg·m−3·d−1. It was necessary to accommodate the important effects of export and exchanges between layers (entrainment flows) associated with reservoir operations in the mass balance framework used to estimate consumption rate(s).

Development and Testing of One-Dimensional Hydrothermal Models of Cannonsville Reservoir

ABSTRACT Two one-dimensional (vertical) hydrothermal models of Cannonsville Reservoir, a water supply serving New York City, were developed and tested. A two-layer model, capable of hindcasting temperature dynamics for two (epilimnion, hypolimnion) completely-mixed, variable-volume layers, was calibrated by determining die seasonal variation of the vertical heat transfer coefficient. This model was used only to hindcast temperature for the spring-fall period of 1995. A multi-layer model (average layer thickness 1.5 m over 50 m maximum depth) was developed that has the capability of forecasting stratification and vertical transport conditions in the reservoir based on specified meteorologic, hydrologic, and reservoir operation conditions. As a part of calibration, the multi-layer model was used to hindcast stratification and vertical transport conditions for the continuous period 1988 through 1995. The model accurately reproduced observed temperature profiles and other observed features such as thermocline depth, rate of hypolimnetic heating, and duration of stratification. A sensitivity analysis indicated that vertical transport of heat to the lower waters of the reservoir in summer is largely associated with advection caused by release of water at the base of the dam; vertical diffusion plays a relatively small role. Model forecasts indicate that stratification characteristics are relatively insensitive to intake location (three intakes over a range of elevation are available), but are more sensitive to the rate of dam release.

Cucumber Flavor in Philadelphia's Drinking Water

Since 1981, when the use of free chlorine was curtailed to control trihalomethanes at the Baxter Treatment Plant in Philadelphia, Pa., a seasonal cucumber flavor problem occurred. Flavor profile analysis was the only tool available to guide treatment. During 1990, the cucumber odor was tracked more than 250 mi (402 km) up the Delaware River to the Cannonsville Reservoir, and the odor‐causing compound was identified as trans,2‐cis, 6‐nonadienal. Algae growth beneath the winter ice produced the compound. Other treatment plants on the river that used free chlorine for disinfection and a final residual never had a problem with trans,2‐cis,6‐nonadienal. Therefore, use of chlorine was increased at the Baxter plant to control the cucumber flavor. Studies were conducted on trans,2‐cis, 6‐nonadienal to describe its sensory characteristics and analytical detection limit.