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Pyke G.,Hazen and Sawyer | Weiss J.,Hazen and Sawyer | Pulokas T.,HydroLogics Inc. | Effler S.,Upstate Freshwater Institute
Watershed Management Conference 2010: Innovations in Watershed Management under Land Use and Climate Change - Proceedings of the 2010 Watershed Management Conference | Year: 2010

The Catskill District of New York City's West-of-Hudson water supply system is one of three major reservoir systems that supply water to New York City and includes Schoharie Reservoir, Shandaken Tunnel, and Ashokan Reservoir. Approximately 40% of the City's average demand is provided by the Catskill System, with an average of 50% and 10% provided by the Delaware and Croton Systems, respectively. The New York City Water Supply System (Figure 1) is operated by the New York City Department of Environmental Protection (NYCDEP) to provide more than 1.1 billion gallons per day of water to more than 9 million customers in the City and the surrounding communities. In the Catskill System, Schoharie Reservoir is fed by a 314-square mile watershed, and diverts up to 615 mgd to Esopus Creek via the Shandaken Tunnel. Esopus Creek drains a watershed of 200 square miles, and flows into Ashokan Reservoir. Water from Ashokan Reservoir is conveyed via the roughly 600-mgd Catskill Aqueduct to Kensico Reservoir, where it mixes with water from the Delaware System before disinfection and delivery to NYC. NYC has maintained a continuous waiver from the federal filtration requirements for its Catskill and Delaware surface water supplies since 1993. In 2002 and 2007, the US EPA issued Filtration Avoidance Determinations (FADs) that classify the Catskill and Delaware Systems as meeting the requirements for an unfiltered water supply given in the Surface Water Treatment Rule (SWTR) and the Interim Enhanced Surface Water Treatment Rule (IESWTR), contingent upon construction of a UV disinfection facility. Due to development in the Croton watershed, the Croton System was not eligible for filtration avoidance; construction is underway on a filtration plant to treat Croton water. Despite the typically pristine nature of the West-of-Hudson supplies, the Catskill System is subject to occasional periods of elevated turbidity levels following major storm events. NYCDEP developed the water supply - water quality modeling framework presented here in order to evaluate alternatives for controlling turbidity in the Catskill reservoirs. This paper describes the development of this modeling tool and its application to Catskill turbidity control issues. © 2011 ASCE. Source


Weiss W.J.,Hazen and Sawyer | Wright B.,Hazen and Sawyer | Sheer D.,HydroLogics Inc.
Watershed Management Conference 2010: Innovations in Watershed Management under Land Use and Climate Change - Proceedings of the 2010 Watershed Management Conference | Year: 2010

Adequate supplies of high quality water are essential both for economic development and basic human survival. As populations continue to rise, municipal supplies, irrigation, power supply, resource extraction, industrial development, recreation, ecological services, and waste disposal will continue to place significant, often conflicting, demands on limited water resources within a region. Increasing scarcity leads to conflicts as existing frameworks for apportioning resources, or lack thereof, cease to function properly such that stakeholder needs are no longer met. Similarly, excessive supplies can result in conflict as well due to flood damage or complaints of water being "wasted" as large volumes flow downstream. Because water is closely connected with our livelihoods, quality of life, and values, water resource disputes can be bitter and seem intractable. Effective management of water resources requires the use of robust, scientifically defensible methods along with collaboration and support of multiple parties to build support for policies or projects. Systems models, which are designed to model a water supply system using hydrologic data and realistic operating rules, can be a tool for achieving these goals. This presentation describes an innovative modeling framework for assisting utilities, regulators, and other watershed stakeholders in developing solutions to complex, multi-objective water management issues and presents a number of applications used in real-world projects to resolve difficult watershed issues. © 2011 ASCE. Source


Sheer A.M.S.,HydroLogics Inc.
Proceedings - 7th International Congress on Environmental Modelling and Software: Bold Visions for Environmental Modeling, iEMSs 2014 | Year: 2014

Active stakeholder participation is critical when trying to find local solutions to environmental problems. When consultants present externally developed suggestions, stakeholders often distrustful. This paper describes a novel methodology that encourages and stakeholder participation, trust, and cooperation while developing model-informed solutions to such issues. This process is illustrated by examples from recent work in the Bow River Basin in Alberta, Canada. The Computer Aided Negotiation process (CAN) is a form of Computer Modelling for Decision Support developed by HydroLogics Inc. and facilitated with OASIS software. It has 4 main stages intended to keep stakeholders engaged and clear difficult problems in advance of the negotiation itself. These stages are: 1. Develop Performance Measures 2. Aggregate/Evaluate Data 3. Build Model 4. Develop and Evaluate Alternatives The key to this process is that each step involves both developing materials for the negotiation itself as well as providing a forum for resolving major disagreements in isolation - i.e. preventing issues from compounding themselves. Data sources, for example, are often contentious. Discussing and developing a data source with the stakeholders prior to modelling allows the stakeholders to trust the model's results. Similarly, developing performance measures at the beginning allows stakeholders to legitimize their interests and gives them an opportunity to dive deeper into what they really want to see in a practical sense. What a stakeholder thinks they want, and what they really want after reflection, may be very different things. Using this process HydroLogics has helped develop solutions in water management for nearly 20 years in both US and international settings. As environmental issues become ever more pressing, these processes have become increasingly critical. Source


Chartrand S.M.,HydroLogics Inc. | Jellinek M.,University of British Columbia | Whiting P.J.,Case Western Reserve University | Stamm J.,South Dakota School of Mines and Technology
Geomorphology | Year: 2011

Understanding the geometric structuring of alluvial step-pools is an enduring problem in mountain stream geomorphology. Many previous studies propose that the key control parameter governing the step-pool form is mean bed slope. As explored through several examples, however, we find that slope control formulations are inconsistently demonstrated for broad data sets. On this basis we reexamine the bed form architecture of step-pools with a new descriptive parameter termed the aspect ratio (α): active stream width divided by step drop height. We test α with data collected from three different mountain settings for step-pools observed over mean bed slopes ranging from 2% to 22%. We find that step wavelength and height are well described by α when these dimensions are normalized by the step drop height; furthermore, we observe that α varies inversely with mean bed slope. Context for our findings is provided by recent field and laboratory work which highlights that the cross-stream component to the overall flow structure in step-pools and scour pools is significant. This is important because it expands upon, and relates our work to formative models which are based on jet scour, and the associated three-dimensional flow structure of step-pools. Our work has practical implications for the design of step-pool channels because existing approaches are based in large part on structuring artificial systems according to a narrowly defined geometry. We observe, however, that under certain conditions this approach may yield constructed step-pools that are unstable. As an alternative approach, we propose that the geometric relationships developed here can be applied to identify artificial step-pool geometries that will be more fully reflective of natural analogs, and thus possibly more stable. © 2011 Elsevier B.V. Source


Caldwell C.,HydroLogics Inc. | Characklis G.W.,University of North Carolina at Chapel Hill
Journal of Water Resources Planning and Management | Year: 2014

Water transfers are one method of allowing utilities to meet demand during dry periods while avoiding, or at least forestalling, the construction of costly new supply capacity. Nonetheless, transfer agreements must have clearly defined terms and decision rules to be effectively implemented. In developing these rules, careful consideration should be given to the risk tolerance of both the buying and selling utilities because these factors can significantly impact the nature of the agreements. This study uses a simulation approach to evaluate interutility transfer agreements that include different mechanisms to reduce risk for both the buyer and seller. For the seller these can include seasonal and volume-based transfer limits that ensure its ability to meet the demands of its own customers before making transfers. For the buyer, important features involve defining the conditions under which it can request transfers, a choice dictated by the buyer's risk tolerance. Several potential agreement structures are considered, with the volume and frequency of transfers as well as the costs varying considerably depending on the risk-reduction mechanisms incorporated. Results indicate that more risk-averse contract structures can significantly increase costs relative to more risk-tolerant scenarios, even though the same reliability objectives are met. While some level of risk aversion is warranted based on uncertainties related to factors such as future demand growth and climate change, the degree of risk aversion justified is a question that deserves greater scrutiny in water resource management plans. In this case, even the most risk-averse agreements were still less expensive than comparable structural alternatives for improving supply reliability. © 2014 American Society of Civil Engineers. Source

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