David M. O'Donnell

Limnological and Loading Information and a Phosphorus Total Maximum Daily Load (TMDL) Analysis for Onondaga Lake

ABSTRACT The phosphorus (P) total maximum daily load (TMDL) analysis and associated management plan for culturally eutrophic Onondaga Lake, NY, are critically evaluated based on available input/discharge and limnological information for the system. The evaluation is based on: (1) results from a long-term monitoring program conducted on the lake, its tributaries, and the adjoining river that receives the lakes outflow, (2) algal bioassay experiments of the bioavailability of particulate P (PP) in inputs to the lake, (3) loading rate calculations for forms of P in these inputs, (4) calculations of water densities in inflows and the lake, (5) model analyses of plunging interflows and responses to seasonal material loading, and (6) mass balance calculations for a tracer conducted around the lake outlet and the receiving river to estimate inflow to the lake from the river. Several important system-specific characteristics were found not to be accommodated in the current TMDL analysis, including: (1) a P load from the river back into the lake, (2)seasonal plunging of tributaries to depths below the productive layers of the lake, (3) incomplete and different bioavailabilities of PP in the various inputs, (4) the different settling velocities of PP from these sources, (5) false high estimates of TP loading from tributaries associated with turbidity interferences in P analyses, and(6)the implications of the high flushing rate of the lake for strong seasonality in the relative impacts of externals loads. The TMDL analysis is demonstrated to understate the present role of the dominant point source and overstate the importance of non-point sources. Recommendations are made to upgrade the TMDL analysis through an integrated program of model development, testing and application, supporting process studies and monitoring, and re-evaluation of management options.

Optical characterizations and pursuit of optical closure for the western basin of Lake Erie through in situ measurements

ABSTRACT In situ measurements of inherent (IOPs) and apparent optical properties (AOPs), along with laboratory measurements of optically active constituents, were made at sites (n = 14) in western Lake Erie following a wind event to advance the characterization of the underwater and emergent light fields of these waters and to support related IOP-based model development and testing. Modern instrumentation was used to make spectral (wavelength,&lgr;) measurements of the IOPs of absorption [a(&lgr;)], particulate scattering ]bp(&lgr;)], and particulate backscattering [bbp(&lgr;)] coefficients, and the AOPs of remote sensing reflectance ]Rrs(&lgr;)], and the diffuse attenuation coefficient for downwelling irradiance [Kd(&lgr;)], Optical closure analyses were conducted to demonstrate the credibility of the measurements, by comparing AOP observations to predictions based on radiative transfer expressions that utilized IOP measurements as inputs. Substantial spectral variations in a and its contributing components, and more modest wavelength dependencies for bp and bbp, were documented that are consistent with observations reported for marine case 2 systems. The backscattering ratio, bbp:bp, was strongly positively related to the contribution of minerogenic particles to the overall concentration of suspended particulate material. Major spatial differences in both IOPs and AOPs were observed that were driven by the attendant differences in the concentrations and composition of the optically active constituents, but particularly minerogenic particles, mediated in part by sediment resuspension. Good optical closure between the independently measured IOPs and AOPs was achieved. Direct measurement of bbp(&lgr;) was found to be critical to pursue closure for Rrs(&lgr;) and thereby support related remote sensing initiatives.

Turbidity and suspended solids levels and loads in a sediment enriched stream: implications for impacted lotic and lentic ecosystems

Abstract The implementation of an automated stream monitoring unit that features four probe-based turbidity (Tn) measurements per hour and the capability to collect frequent (e.g., hourly) samples for total suspended solids (TSS) analyses during runoff events to assess the dynamics of Tn, TSS and corresponding loads in sediment-rich Onondaga Creek, NY, was documented. Major increases in both Tn (maximum of 3,500 NTU) and TSS (maximum of 1630 mg/L) were reported for the stream during runoff events. Relationships between Tn, TSS and stream flow (Q) were developed and applied to support estimates of TSS loading (TSSL). Tn was demonstrated to be a better predictor of TSS than Q, supporting the use of the frequent field Tn measurements to estimate TSSL. During the year of intensive monitoring, 65% of the TSSL was delivered during the six largest runoff events that represented 18% of the annual flow. The high Tn levels and extensive in-stream deposition have negatively impacted the streams biota and the esthetics of a downstream harbor. Onondaga Creek is reported to be the dominant allochthonous source of inorganic particulate material to downstream Onondaga Lake. These sediment inputs have important implications for the lake, within the context of two on-going rehabilitation programs aimed at contaminated lake sediments and the effects of extreme cultural eutrophication, by contributing substantially to sedimentation and turbidity. A satellite image documented the occurrence of a conspicuous turbidity plume that emanated from Onondaga Creek following a minor runoff event, suggesting such an effect is common and that related impacts are not spatially uniform.

America’s Most Polluted Lake:Using Robotic Buoys to Monitor the Rehabilitation of Onondaga Lake

have resulted in the most extreme cases of water pollution. Invaluable local fresh water resources have been lost as part of the development and activities of urban areas associated with increasing levels of discharge of waterborne pollutants. Substantial damage was done before there was full scientific understanding of the implications of the discharges and before there were technological solutions and alternatives. Major improvements in the ecological and water quality conditions of fresh waters have been achieved in recent years in many urban areas based on advancements in the scientific understanding of society’s impacts on water quality, technologies of wastewater treatment, and implementation of these technologies. These efforts have been driven both by public health concerns and the desire of communities to recover resource uses of these surface waters (e.g., recre-

The effect of municipal wastewater effluent on nitrogen levels in Onondaga Lake, a 36-year record.

This work presents a retrospective analysis of long-term trends in loading of forms of nitrogen (N) from the Metropolitan Syracuse Wastewater Treatment Plant (Metro), N concentrations in the receiving urban lake (Onondaga Lake, New York), and related water quality status for the period from 1972 to 2007. The history of the evolution of treatment and discharge at Metro, as it affected N loading, is reviewed and forms the basis for identification of five regimes during which unifying conditions of loading and in-lake conditions prevailed. Changes in industrial waste inputs have complicated the effects of upgrades in treatment at Metro from primary (until 1978) to advanced (starting in 2004). Current N loading from Metro is approximately 35% lower than the peak levels observed in the late 1980s to late 1990s, but the areal rate to the lake remains extremely high (approximately 97 g/m(2).y), representing approximately 75% of the overall N load. Implementation of year-round nitrification treatment has resulted in transformation of the composition of the N load from Metro from ammonia (T-NH3) to nitrate (NO3(-)) dominance. High N concentrations have prevailed in the upper waters of the lake throughout the study period with averages of total N ranging from 2.6 to 4.3 mg/L for the five regimes. Total N levels and partitioning among the forms in the lake generally have tracked Metro loading conditions for the five regimes. The effects of Metro loading on seasonal in-lake patterns are demonstrated to be modified by both hydrologic inputs from tributaries and in-lake operation of biochemical processes. Resolution of these effects is supported by application of both empirical and dynamic mass balance models. Water quality problems related to high concentrations of forms of N are documented, including (1) augmentation of dissolved oxygen depletion during fall mixing from in-lake nitrification events, enabled by high T-NH3 levels; (2) violations of ammonia toxicity limits; and (3) violations of nitrite toxicity standards. These problems were either greatly ameliorated or eliminated by Metros most recent treatment upgrades. Prevailing conditions are considered in a management context, including (1) likelihood of exceedances of toxicity limits in the future and (2) potential role of elevated nitrate levels in preventing mobilization of methyl mercury from the lakes sediments.

Insights for the structure of a reservoir turbidity model from monitoring and process studies

Abstract An array of in situ and laboratory measurements were made and in situ settling velocity experiments were conducted to support identification of model structure features necessary to simulate transient turbidity impacts in Schoharie Reservoir, NY, from runoff events. The program included: (1) extended deployments of recording instruments measuring temperature (T) and specific conductivity (SC) in the primary tributary and the reservoir surface waters; (2) automatic sampling of the tributary during runoff events for laboratory turbidity (Tn) measurements; (3) collection of vertically detailed profiles of T, SC, and the beam attenuation coefficient at 660 nm (c660; a surrogate of Tn) at multiple sites along the longitudinal and lateral axes of the reservoir with rapid profiling instrumentation; (4) chemical and morphometric characterizations of individual particles from the tributary and reservoir during dry weather conditions and for a runoff event with scanning electron microscopy coupled with automated image analysis and X-ray microanalysis (SAX); and (5) in situ measurements of settling velocity (SV) as a function of particle size with a LISST-ST®. A strong positive relationship between Tn, associated primarily with clay minerals, and tributary flow (Q), and a negative relationship between SC and Q, were reported. The entry of the primary tributary as a plunging turbid density current because of its lower T, and associated spatial and temporal patterns in c660 and SC imparted in the reservoir, were documented for two runoff events. SC was identified as a viable tracer of the movement of density currents in the reservoir, and the internal contribution of resuspension to c660 levels was depicted. The results of SAX analyses demonstrated a substantial fraction (i.e., 30–40%) of the Tn that enters the reservoir from the primary tributary was associated with particles >9.1 μm in diameter that do not contribute to Tn levels in the lacustrine portions of the reservoir. Higher SV values were observed for larger particles, but were much lower than Stokes Law conditions, suggesting that they existed as aggregates. The monitoring and SV experiment results were considered within the context of the structural needs of turbidity models, for two levels of complexity, to simulate the transient impacts of runoff events on the reservoir. A two- or three-dimensional transport submodel will be necessary to represent spatial patterns, and a kinetics submodel will need to represent (either implicitly or explicitly) size dependent settling, particle coagulation, and sediment resus-pension.

Comparison of an Urban Lake Targeted for Rehabilitation and a Reference Lake Based on Robotic Monitoring

Abstract A reference lake, Otisco Lake, NY, was selected to evaluate rehabilitation initiatives to mitigate severe cultural eutrophication of Onondaga Lake, NY. Onondaga Lake was mesotrophic before European development. The reference lake selection was based on an analysis of paired monitoring datasets for temperature, fluorometric chlorophyll (Chlf/a) and dissolved oxygen (DO), collected daily by robotic profiling platforms for the spring to fall interval of three years. The various metrics of trophic state documented here for Otisco Lake represent reasonable informal interim goals for the rehabilitation of the cultural eutrophication of Onondaga Lake. The use of Otisco Lake as a reference site is supported by its similar stratification/mixing regime and mesotrophic state, in addition to its proximity (~25 km) and similar morphometry with Onondaga Lake. Strong contrasts in water quality manifestations of trophic state are depicted in Onondaga Lake, including higher Chlf/a (3.5-fold), prevalence of blooms, greater deviations of DO from saturation conditions, much lower minimum DO values at fall turnover in the upper layers and a higher volumetric hypolimnetic oxygen deficit (VHOD; 1.55-fold). Advantages of the fine vertical and temporal scale capabilities of the monitoring platforms are demonstrated in characterizing these and other limnological features. Continued robotic monitoring at Otisco Lake as a reference site and Onondaga Lake through the rehabilitation program will support ongoing comparisons to assess progress and will help engage stakeholders in the process.

Resolution of spatial patterns in three reservoirs with rapid profiling instrumentation

Rapid profiling instrumentation is used to resolve spatial patterns of temperature (T), specific conductance (SC), chlorophyll (Chl) and beam attenuation (c660), in three dimensional space for three water supply reservoirs (Pepacton, Rondout and Ashokan) located in New York State, U.S.A. Conspicuous patterns depict the operation of important processes that include the development of deep chlorophyll maxima, the entry of major tributary and tunnel inflows as interflows, and the development of benthic nepheloid layers. SC is demonstrated to be a valuable tracer of the interflow process in these reservoirs. Distinct longitudinal structures are documented for T in spring, SC, Chl and c660, along the major axes of Pepacton, Rondout, and one of the two (separated) basins of Ashokan. Substantial differences are demonstrated to prevail between the two basins of Ashokan; treatment as two basins in series is recommended for modeling purposes. Three-dimensional structures in SC and c660, apparently imparted from interflows, are documented for one of the basins of this impoundment. The needs of mechanistic model frameworks to accommodate the observed spatial patterns and processes are considered.

Turbidity and temperature patterns in a reservoir and its primary tributary from robotic monitoring: Implications for managing the quality of withdrawals

Abstract A robotic water quality monitoring network, consisting of 2 in-reservoir profiling platforms and a unit positioned in the primary tributary, was used to document patterns of temperature (T) and turbidity (Tn) and the impact of runoff events on Tn levels over the spring to fall interval of 3 years. The patterns were evaluated in the context of water quality goals for T and Tn for reservoir withdrawal and potential benefits of specified management alternatives. Exceedences of a proposed withdrawal T goal of 21.1 °C (70 °F) and a conservative representation of the Tn goal of 15 NTU were demonstrated. The exceedences occurred in late summer during intervals of extensive drawdown for T and irregularly following runoff events for Tn. Conspicuous increases in Tn in the tributary and lacustrine portions of the reservoir were demonstrated in response to all monitored runoff events (n = 34). Lacustrine levels exceeded 75 NTU following several major events. The turbidity load from the tributary usually enters the reservoir as a turbid density current during runoff events, at a depth predicted well by stream temperature. The high frequency and vertical resolution attributes of the robotic monitoring (2 profiles per day for reservoir deployments) were invaluable in resolving impacts because these were usually attenuated within a week following events. The diminishment of reservoir Tn levels following events was demonstrated to be well represented by a first-order loss rate. The loss rate for the largest runoff event of the study (return interval ~25 y) was more than an order of magnitude lower than any other, indicating a difference in settling attributes of turbidity-causing particles for this extreme case. Benefits from a shift to delayed withdrawals for the existing intake, or installation of a multi-level intake facility, for improving status with respect to the water quality goals are suggested from the monitoring data. However, continuously meeting the Tn goals for particularly severe events may not be feasible through these approaches.

Use of Robotic Monitoring to Assess Turbidity Patterns in Onondaga Lake, NY

Abstract Selected temporal and vertical patterns of turbidity (Tn) are documented for an eutrophic urban lake, Onondaga Lake, NY, and their diagnostic value in identifying hydrodynamic and metabolic processes and in estimating clarity is established. The analysis is supported by five years (spring to fall) of daily robotic profiling of Tn, temperature (T), and dissolved oxygen, and an array of more temporally limited measurements that included Tn and T levels in the major tributary input of terrigenous solids; lake particle characterizations with a profiling particle counter and a scanning electron microscope coupled with automated image analysis and X-ray microanalysis; and Secchi disc transparency (SD). Major runoff events are demonstrated to cause conspicuous short-term increases in Tn that are manifested as metalimnetic peaks in summer and early fall, associated with the entry of the negatively buoyant primary tributary source as an interflow. The annual occurrence of Tn maxima within the oxycline of the metalimnion in October is documented. Evidence supports the position that this layer is a bacterial plate of oxidizing bacteria that develops seasonally in response to increasing vertical transport of reduced species from the hypolimnion with the approach to fall turnover. A strong relationship between SD and Tn in the upper waters is reported, that is demonstrated to have utility in resolving the dynamics of substantial changes in SD that occur in the lake during clear water phases.