Ground Water Vulnerability Assessment Predicting Relative Contamination Potential Under Conditions of Uncertainty (1993) / Chapter Skim
Currently Skimming:
2 Considerations in the Selection and Use of Vulnerability Assessments
2 Considerations in the Selection and Use of Vulnerability Assessments
Pages 30-41
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 30... ...
containing the results of sophisticated models representing complex ground water processes and sometimes questionable data. An important corollary to the Second Law of Ground Water Vulnerability is that since all vulnerability assessments are uncertain, no management decisions based on them are ever clear-cut or certain.
|
From page 31... ...
First, assessments can be used in policy analysis and development to identify the potential for ground water contamination and the need for protection and to aid in examining of the relative effects of alternative ways to control contamination. Second, when scarce resources prevent uniform and costly expenditures, vulnerability assessments can be used in program management to allocate resources to areas where the greatest effort is warranted.
|
From page 32... ...
These purposes could vary from providing the greatest benefit or protection with the least expenditure to preventing the worst possible contamination problem. For example, vulnerability assessments could be used to establish routine ground water monitoring programs, to establish databases, or to ensure compliance with standards or other protection requirements.
|
From page 33... ...
Land use decision making thus tends to be highly decentralized, and the application of ground water vulnerability assessments to such decisions presents special technical and institutional problems. Still, ground water vulnerability assessments may inform three principal categories of land use decision making: zoning and screening functions; permit conditioning, mitigation, and monitoring; and the voluntary behaviors of individual land users and authority over land use.
|
From page 34... ...
While it might be tempting to construct a hypothetical ground water zoning map based on a vulnerability map, such a zoning map could not of course, be more detailed or more certain than the underlying vulnerability assessment. Unfounded application of regional assessments at the site level could result in misinformed decisions with unfortunate and even tragic consequences for the land user, land regulator, and the ground water resource itself.
|
From page 35... ...
Again, the utility of the vulnerability assessment in technical assistance will depend on its specificity, level of detail, and degree of uncertainty. General Education and Awareness Although vulnerability assessments are rarely undertaken primarily to increase the awareness and knowledge of the public and decision makers on the potential for contamination of ground water resources, that may be their most valuable use.
|
From page 36... ...
Technical Considerations Many technical issues affect the design and use of vulnerability assessments. They include the type and form of the results or output, the suitability of the technique for the physical characteristics of the area being assessed, the adequacy of the available data or data to be collected, and the analysis of uncertainty in the output and how it may affect the actions influenced by the assessment.
|
From page 37... ...
As a rule of thumb, the mathematical complexity of the vulnerability assessment technique is inversely related to the size of the area being assessed. For smaller regions, on the level of a watershed or field, the vulnerability assessment technique may include numerical models of the physical processes of vadose-zone hydrologic flow and chemical transport and fate.
|
From page 38... ...
Because these types of data are less tied to specific physical measurements, and because the geographic regions will vary from assessment to assessment, it is difficult to set standards for data collection and aggregation for these methods. For any type of analysis, the quality of the data will affect the level of uncertainty associated with the assessment results.
|
From page 39... ...
As noted in Chapter 1, sufficiently persistent and mobile contaminants may eventually be observed in ground water at significant levels even though the travel times may be long. Thus, it may be necessary to consider effects on ground water quality over longer time spans and greater distances than is commonly done in vulnerability assessments.
|
From page 40... ...
If the vulnerability assessment is to be a one-time activity for example, a survey of the status of a region's ground water the approach would likely be to use existing data with a readily available assessment method to produce results in relatively short order. On the other hand, a vulnerability assessment can be part of a long-term program to develop and monitor ground water protection strategies and intervention measures.
|
From page 41... ...
In addition, scientists should seek better methods for communicating underlying uncertainties to managers who may not have extensive technical training. Better communication among scientists and managers should surely improve the development of useful and valid vulnerability assessments and the soundness of policies informed by them.
|
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.