Clean Coastal Waters Understanding and Reducing the Effects of Nutrient Pollution (2000) / Chapter Skim
Currently Skimming:
7 The Role of Monitoring and Modeling
7 The Role of Monitoring and Modeling
Pages 195-236
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 195... ...
Understanding Abatement Strategies
|
From page 196... ...
The Long Island Sound nutrient input analysis illustrates the problems that can be encountered by applying export coefficient models in an area of high atmospheric deposition of nitrogen. The Long Island Sound study concludes that most of the nonpoint inputs of nitrogen to Long Island Sound come from natural sources not subject to human control (CDEP and NYSDEC 1998~.
|
From page 197... ...
· Effective marine environmental monitoring programs must have clearly defined goals and objectives; a technical design based on an understanding of system linkages and processes; testable questions and hypotheses; peer review; methods that employ statistically valid observations and predictive models; and the means to translate data into information products tailored to the needs of their users, including decisionmakers and the public. · There is no simple formula to ensure a successful monitoring program.
|
From page 198... ...
Monitoring can play an important role in understanding and mitigating nutrient over-enrichment problems by helping pinpoint the nature and extent of problems. Because nutrient over-enrichment often results in local problems, the management responses, including monitoring programs, is typically local.
|
From page 199... ...
Typical monitoring programs are built around fixed devices and sampling schemes. To design an appropriate sampling scheme, an estimate of the important scales of variability must be made.
|
From page 200... ...
Many mathematically simple models require extensive and expensive monitoring programs to provide data before they can produce accurate results. Thus, the level of model sophistication does not necessarily indicate savings in the resources that must be devoted to monitoring in order to produce accurate hindcasts or predictions.
|
From page 201... ...
Focused monitoring programs are generally established in response to, rather than in anticipation of, a problem. This means that baseline information can be missing from a monitored region.
|
From page 202... ...
The internet offers a relatively simple, widely accessible route for distribution. ELEMENTS OF AN EFFECTIVE MONITORING PROGRAM Effective marine environmental monitoring programs must have the following features: clearly defined goals and objectives; a technical design that is based on an understanding of system linkages and processes; testable questions and hypotheses; peer review; methods that employ statistically valid observations and predictive models; and the means to translate data into information products tailored to the needs of their users, including decisionmakers and the public (NRC 1990~.
|
From page 203... ...
Objectives and information needs must be defined before the program design decisions can be made rationally. Successful monitoring programs strive to gather the long time series data needed for trend detection, but at the same time must be flexible to allow reallocation of resources during the program.
|
From page 206... ...
Monitoring is often targeted to study more characteristics than simply the eutrophication of a particular coastal waterbody. Often, monitoring programs focus broadly on health of the ecosystem.
|
From page 207... ...
Unfortunately, the political will to maintain long-term funding for monitoring programs is often lacking because such programs rarely (and were never intended to) produce major breakthroughs in understanding.
|
From page 208... ...
The final step in design of any successful monitoring program should be establishment of a process of independent review and, if necessary, protocol modification. Such reviews are necessary for monitoring programs to take advantage of new measurement and analysis techniques, and they help determine if programs are effectively answering the questions for which they were designed.
|
From page 209... ...
No such consistent, coherent monitoring program now exists. One program, the Environmental Protection Agency's (EPA)
|
From page 210... ...
DEVELOPING QUANTITATIVE MEASURES OF WATERSHED CONDITIONS For a number of reasons, the development of watershed monitoring programs has proceeded for many years relatively independently of receiving water monitoring programs. The relative temporal stability of terrestrial distributions, when compared to estuarine and coastal distributions, has resulted in the development of map-based studies.
|
From page 211... ...
Effective monitoring strategies, however, must be spatially extensive as well as sufficiently frequent to detect real and statistically valid changes. Unfortunately, the outcomes and benefits of most monitoring programs will not be manifested for several years before yielding useful information.
|
From page 212... ...
1996~. Therefore, environmental threshold soil phosphorus levels will have little value unless they are used with estimates of site-specific potential for surface runoff and erosion.
|
From page 213... ...
This, in turn, implies that similar water quality standards, criteria, and monitoring strategies are likely to be valid in a given ecoregion (EPA 1996~. CONTROLLING COSTS As with all extensive monitoring programs, one of the main chal
|
From page 214... ...
In the Chesapeake Bay area, for instance, stakeholder alliances have developed among state, federal, and local groups to work together to identify critical problems, focus resources, include watershed goals in planning, and implement effective strategies to safeguard soil and water resources (Chesapeake Bay Program 1995, 1998~. INTRODUCTION TO MODELING One system is said to model another when the observable parameters in the first system vary in the same fashion as the observable parameters in the second.
|
From page 216... ...
Numerical models are most useful when they are based on first principles. The ability to describe system functions in terms of mathematical equations often gives the impression that the underlying principles are fully understood, as might be the situation in basic physics.
|
From page 217... ...
General guidance in evaluation of the goodness-of-fit of hydrologic and water quality models that produce time series of hydrographs and quality parameters is provided by Legates and McCabe (1999~. Such efforts are a necessary but time-consuming and costly undertaking.
|
From page 218... ...
In the absence of data for the watershed or receiving waterbody being studied, it should be demonstrated that the model satisfactorily represents the same physical processes on a similar watershed or waterbody. At worst, model output should be compared to +50 % Change in Output ~ O More Less Sensitive / Sensitive / ~ / I / -50 / O -- - +50 / \ / -50 / % Change in Input + FIGURE 7-2 Example of sensitivity analysis: the relative change in an output variable from a model due to the relative change in an input variable to a model.
|
From page 219... ...
(1995) compare two years of North Sea nutrient concentration and phytoplankton data, with the annual cycle of the same parameters derived from the European Regional Seas Ecosystem Model (Baretta et al.
|
From page 220... ...
Solid, continuous lines show the model output; dots with lines represent observations (mean and observed variability)
|
From page 223... ...
For example, they often fail to reproduce important smallscale blooms. In spite of the effort and resources expended on the Chesapeake Bay model, for instance, it has been suggested that "three caveats need to be appreciated in interpretations of the watershed-water quality models: (1)
|
From page 224... ...
Whenever possible, this uncertainty should be represented in the model output (e.g., as a mean plus a standard deviation) or as confidence limits on the output of a time series of concentrations or flows.
|
From page 225... ...
coupled with export coefficients or event mean concentrations. These models are sometimes called spreadsheet approaches, but they actually can be highly sophisticated.
|
From page 226... ...
Such a database would be of inestimable value for developing loading estimates to receiving waters. Consequently, as the agency responsible for implementing National Pollutant Discharge Elimination System legislation, EPA should develop and maintain a current nationwide database of urban and other surface runoff samples for use in nonpoint source water quality analyses and modeling.
|
From page 227... ...
. Several watershed models can be run in either mode, and fast computers with extensive memory make the distinction between degree of schematization and time step less of an issue.
|
From page 228... ...
Agencies that sponsor watershed and water quality models should also sponsor development of databases of typical modeling parameters and case studies (bibliographic databases) of modeling efforts.
|
From page 229... ...
As with the watershed models described above, estuarine and coastal models can be segregated into a small set of model types (EPA 1990~.
|
From page 230... ...
Most estuarine water quality models are formulated around phytoplankton-based primary production, but in some instances it may be important to focus on macrophytes. Special models have been developed to treat such situations (Box 7-4~.
|
From page 231... ...
Carbon is distributed among pools with different turnover rates, which depend on the plant lignin content. The time step of the original model was one month, so short-scale meteorological varia
|
From page 232... ...
1998) have shortened the model time step to one day, and added runoff processes and multiple layers to the soil model.
|
From page 233... ...
A related issue is linking models that were developed for different purposes. For instance, it is not necessarily a simple task to input a time series of atmospheric deposition values into a watershed loading model or a receiving water quality model.
|
From page 234... ...
Army Corps of Engineers' Hydrologic Engineering Center. For receiving water quality models, EPA, and the U.S.
|
From page 235... ...
Data sets of input parameters for calibrated models should be provided by the agencies charged with oversight of the models. Agencies that sponsor watershed and water quality models should also sponsor development of databases of typical modeling parameters and a bibliographic database of case studies of model applications.
|
From page 236... ...
The present lack of knowledge concerning the connections among nutrient loadings, phytoplankton community response, and higher trophic levels implies a disconnection between the estimates used to evaluate management scenarios and the goals for which management is taking place. Therefore, the development of heuristic models using comparative ecosystem approaches is needed to identify and better understand key processes and their controls in estuaries.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.