Hydrophysical and Ecological Modelling of Deep Lakes and Reservoirs: Summary Report of an IIASA Workshop, December 1977

A series of questions related to the geophysical and ecological modelling of deep lakes and reservoirs were formulated and distributed in advance of the workshop. This workshop report summarizes the discussion of each of the questions relating to the following topics: element cycles, nutrient uptake and grazing rates by phytoplankton and zooplankton, single versus multi-layer models, vertical mixing and diffusion, lake circulation and methods of parameter estimation

Modeling Wind-Driven Circulation in Lake Balaton

This paper reports the results achieved to date in a program of research to develop and apply mathematical computer models of water quality in shallow lakes. The portion of the research which is the specific topic of this paper is the development, testing and trial application of a transient three-dimensional model of wind-driven circulation. The results are presented in the context of an application to Lake Balaton in Hungary, a large yet very shallow lake. The paper presents a review of the mathematical formulation of the circulation problem and the major methods used in computer models of wind-driven circulation. Detailed examinations of the model assumptions and parameters are also included. A description of the application lake follows and a three-dimensional model appropriate to shallow lakes is proposed and derived. This model is examined for consistency with Lake Balaton's characteristics, and the important need for congruence with an eventual coupled biogeochemical model of the water quality is described and investigated. The requirement that the length and time scales of the hydrodynamic model and the biogeochemical model be consistent with each other and with the processes of interest in the lake is stressed. The proposed circulation model employs a Galerkin technique to compute the vertical velocity profile using a depth-dependent vertical eddy viscosity. The parameters for this model are determined by calibration using simple hypothetical seiche simulations as a standard. It is found that the function specified for the vertical eddy viscosity is a crucial determinant of the model response. The resulting model and calibration are then successfully verified with historical events on Lake Balaton. A detailed examination of the results of one of these event simulations explores aspects of the model predictions pertinent to the mass transport of water quality constituents. Conclusions of the paper include identification of the need to improve the representation of mass transport in existing models of Balaton's water quality and an agenda for future development of a coupled hydrodynamic-biogeochemical water quality model

Waste heat management in the electric power industry : issues of energy conservation and station operation under environmental constraints

Over the past three years, the Energy Laboratory, in cooperation with the R.M. Parsons Laboratory for Water Resources and Hydrodynamics at M.I.T. has been under contract with DOE/ECT to study various water and waste heat management issues associated with the choice of cooling systems for large steam-electric power plants. The purpose of this report is to summarize the major findings to-date of this study. In addition, an introduction or background section proceeds the summary so that the results can be better integrated into the larger picture of water and waste heat management.Over the past three years, the Energy Laboratory, in cooperation with the R.M. Parsons Laboratory for Water Resources and Hydrodynamics at M.I.T. has been under contract with DOE/ECT to study various water and waste heat management issues associated with the choice of cooling systems for large steam-electric power plants. The purpose of this report is to summarize the major findings to-date of this study. In addition, an introduction or background section proceeds the summary so that the results can be better integrated into the larger picture of water and waste heat management

Three Essays on the Economic Well-Being of Communities Near Energy Development

Recent United States energy policies have sought to reduce greenhouse gas emissions while keeping fuel and electricity prices affordable. For example, continued promotion of the burgeoning natural gas and renewable energy industries, along with the installation of new utility infrastructure, could provide extensive economic benefits. However, in each of these industries, local communities have faced disamenities, often without sharing in the associated benefits. Citizens have responded by opposing development, resulting in outcomes that range from delays caused by prolonged zoning hearings, to statewide bans on unconventional natural gas development. This suggests that policymakers must understand and address disamenities, or else risk the creation of inequities or the prevention of otherwise welfare improving investments. This dissertation is comprised of three essays, each of which aims to develop our understanding of the distribution of costs and benefits near energy developments, and the extent to which public policy can modify them to promote the well-being of both local communities and society

The mechanics of submerged multiport diffusers for bouyant discharges in shallow water

Prepared by the Ralph M. Parsons Laboratory for Water Resources and Hydrodynamics in association with the Energy LaboratoryA submerged multiport diffuser is an effective device for disposal of water containing heat or other degradable wastes into a natural body of water. A high degree of dilution can be obtained and the environmental impact of concentrated waste can be constrained to a small area. An analytical and experimental investigation is conducted for the purpose of developing predictive methods for buoyant discharges from submerged multiport diffusers. The following physical situation is considered: A multiport diffuser with given length, nozzle spacing and vertical angle of nozzles is located on the bottom of a large body of water of uniform depth. The ambient water is unstratified and may be stagnant or have a uniform current which runs at an arbitrary angle to the axis of the diffuser. The general case of a diffuser in arbitrary depth of water and arbitrary buoyancy is treated. However, emphasis is put on the diffuser in shallow receiving water with low buoyancy, the type used for discharge of condenser cooling water from thermal power plants. A multiport diffuser will produce a general three-dimensional flow field. Yet the predominantly two-dimensional flow which is postulated to exist in the center portion of the three-dimensional diffuser cart be analyzed as a two-dimensional "channel model", that is a diffuser section bounded by walls of finite length and openings at both ends into a large reservoir. Matching of the solutions for the four distinct flow regions which can be discerned in the channel model, namely, a buoyant jet region, a surface impingement region, an internal hydraulic jump region and a stratified counterflow region, yields these results: The near-field zone is stable only for a limited range of jet densimetric Froude numbers and relative depths. The stability is also dependent on the jet discharge angle. It is only in this limited range that previous buoyant jet models assuming an unbounded receiving water are applicable to predict dilutions. Outside of the parameter range which yields stable near-field conditions, the diffuser-induced dilutions are essentially determined by the interplay of two factors: frictional effects in the far-field and the horizontal momentum input of the jet discharge. Three far-field flow configurations are possible, a counter flow system, a stagnant wedge system and a vertically fully mixed flow, which is the extreme case of surface and bottom interaction. A three-dimensional model for the diffuser-induced flow field is developed. Based on equivalency of far-field effects, the predictions of the two-dimensional channel model can be linked to the three-dimensional diffuser characteristics. Diffusers with an unstable near-field produce three-dimensional circulations which lead to recirculation at the diffuser line: effective control of these circulations is possible through horizontal nozzle orientation. The diffuser in an ambient cross-current is studied experimentally. Different extreme regimes of diffuser behaviour can be described. Performance is dependent on the arrangement of the diffuser axis with respect to the crossflow direction. Experiments are performed in two set-ups, investigating both two- dimensional slots and three-dimensional diffusers. Good agreement between theoretical predictions and experimental results is found. The results of this study are presented in form of dilution graphs which can be used for three-dimensional diffuser design or preliminary design if proper schematization of the ambient geometry is possible. Design considerations are discussed and examples are given. For more complicated ambient conditions, hydraulic scale models are necessary. The results of this study indicate that only undistorted scale models simulate the correct areal extent of the temperature field and the interaction with currents, but are always somewhat conservative in dilution prediction. The degree of conservatism can be estimated. Distorted models are less conservative in predicting near-field dilutions, but exaggerate the extent of the near-field mixing zone.Stone and Webster Engineering Corp., Boston, Mass., Long Island Lighting Co., Hicksville, New York, and the National Science Foundation, Engineering Energetics Program. GK-3247

A Comparison of Water Quality Models of the Aerobic Nitrogen Cycle

The objective is to compare a sequence of biochemical water quality models of increasing complexity and diversity, in order to determine the level of complexity needed for predictive models. Primary consideration will be given to models simulating chemical, bacterial and algal components that can be compared with laboratory data. The aerobic nitrogen cycle containing seven chemical and biological components of nitrogen is chosen for the comparative study. The nitrogen components can be coupled by various linear and/or non-linear transformation functions representing mineralization and oxidation of organic nitrogen and phytoplankton-zooplankton interactions. Results of simulation runs for batch systems are compared with the same data. It is concluded that the non-linear couplings, representing bacterially mediated and plankton reactions, have a significant influence on both the system dynamics and the steady state nitrogen concentrations. Future research directions for comparative model studies are indicated

Stability and mixing of submerged turbulent jets at low Reynolds numbers

Originally presented as the first author's thesis (M.S.), Temperature reduction in a submerged vertical jet in the laminar-turbulent transition, M.I.T. Dept. of Civil EngineeringAn experimental study is made of the variation of volume and centerline dilution as a function of Reynolds number in non- buoyant and buoyant round jets discharged vertically from a submerged nozzle. The jet Reynolds numbers covered the laminar- turbulent transition with values ranging from Re = u D/v = 100 to 20,000 where u = jet exit velocity, D = jet diameter, and V = kinematic viscosity. Measurements of jet temperature profiles are obtained by using both fast and slow thermistor probes. Turbulent dilution is found to be independent of Reynolds number for non-buoyant jets above a critical Reynolds number of about 1,500. For buoyant jets (densimetric Froude numbers in the range 25 to 50), the critical Reynolds number is about 1,200. Reasonable agreement is obtained with the results of previous investigators for dilution values at high Reynolds numbers. Dye studies of transition Reynolds numbers are compared with a study by A.F. Pearce (1966) and good agreement is found. The results are useful in determining the minimum length scale ratio for hydro-thermal model studies, especially those of submerged multiport diffusers. It is concluded that modeling of turbulent jets is acceptable provided the model Reynolds number is larger than the critical Reynolds number and provided no other constraint becomes binding. In addition, the model jet's laminar length, if any, must be insignificant when compared to the total length of the path of the jet.New England Electric System and Northeast Utilities Service Company under the M.I.T. Energy Laboratory Electric Power Progra

Applying the COM-B model to creation of an IT-enabled health coaching and resource linkage program for low-income Latina moms with recent gestational diabetes: the STAR MAMA program.

BACKGROUND:One of the fastest growing risk groups for early onset of diabetes is women with a recent pregnancy complicated by gestational diabetes, and for this group, Latinas are the largest at-risk group in the USA. Although evidence-based interventions, such as the Diabetes Prevention Program (DPP), which focuses on low-cost changes in eating, physical activity and weight management can lower diabetes risk and delay onset, these programs have yet to be tailored to postpartum Latina women. This study aims to tailor a IT-enabled health communication program to promote DPP-concordant behavior change among postpartum Latina women with recent gestational diabetes. The COM-B model (incorporating Capability, Opportunity, and Motivational behavioral barriers and enablers) and the Behavior Change Wheel (BCW) framework, convey a theoretically based approach for intervention development. We combined a health literacy-tailored health IT tool for reaching ethnic minority patients with diabetes with a BCW-based approach to develop a health coaching intervention targeted to postpartum Latina women with recent gestational diabetes. Current evidence, four focus groups (n = 22 participants), and input from a Regional Consortium of health care providers, diabetes experts, and health literacy practitioners informed the intervention development. Thematic analysis of focus group data used the COM-B model to determine content. Relevant cultural, theoretical, and technological components that underpin the design and development of the intervention were selected using the BCW framework. RESULTS:STAR MAMA delivers DPP content in Spanish and English using health communication strategies to: (1) validate the emotions and experiences postpartum women struggle with; (2) encourage integration of prevention strategies into family life through mothers becoming intergenerational custodians of health; and (3) increase social and material supports through referral to social networks, health coaches, and community resources. Feasibility, acceptability, and health-related outcomes (weight loss, physical activity, consumption of healthy foods, breastfeeding, and glucose screening) will be evaluated at 9 months postpartum using a randomized controlled trial design. CONCLUSIONS:STAR MAMA provides a DPP-based intervention that integrates theory-based design steps. Through systematic use of behavioral theory to inform intervention development, STAR MAMA may represent a strategy to develop health IT intervention tools to meet the needs of diverse populations. TRIAL REGISTRATION:ClinicalTrials.gov NCT02240420

Stability and mixing of a vertical round buoyant jet in shallow water

Also issued as a M.S. thesis in the Department of Civil Engineering at Massachusetts Institute of TechnologyDischarging heated water through submerged vertical round ports located at the bottom of a receiving water body is a currently used method of waste heat disposal. The prediction of the temperature reduction in the near field of the buoyant jet is a problem of environmental concern. The mechanics of a vertical axisymmetric buoyant jet in shallow water is theoretically and experimentally investigated. Four flow regimes with distinct hydrodynamic properties are discerned in the vicinity of the jet: the buoyant jet region, the surface impingement region, the internal hydraulic jump, and the stratified counterflow region. An analytical framework is formulated for each region. The coupling of the solutions of the four regions yields a prediction of the near field stability as well as the temperature reduction of the buoyant discharge. It is found that the near field of the buoyant jet is stable only for a range of jet densimetric Froude numbers and submergences. A theoretical solution is given for the stability criterion and the dilution of an unstable buoyant jet. A series of experiments were conducted to verify the theory. The experimental results are compared to the theoretical predictions. Good agreement is obtained

Can Collective Action Institutions Outperform the State? Evidence from Treatment of Abandoned Mine Drainage.

A core public administration literature seeks to understand whether decentralized collective action institutions will emerge to provide public goods, such as management of environmental resources. Few studies examine how they perform relative to the state at providing public goods, and they fail to account for the possibility that the state might self-select into providing public goods in the most challenging contexts. If it does, finding that the state performs worse than collective action institutions could reflect its more challenging context rather than differences in knowledge, skill, or motivation. We examine several quantitative measures of performance in remediating polluted water discharges from abandoned coal mines in Pennsylvania, a task sometimes done by the state and sometimes by nonprofit watershed associations. We find that the two types of institutions address discharges with generally similar water quality problems and build systems that yield similar initial improvements in water quality. However, watershed association systems better maintain effectiveness at reducing acidity and removing heavy metals over time. The findings suggest a role for sustained public investment in collective action institutions to address complex and enduring environmental problems