Presentation on theme: "DRASTIc Groundwater Vulnerability map of Tennessee"— Presentation transcript:
1 DRASTIc Groundwater Vulnerability map of Tennessee James Bond – Capstone ProposalGEOG 596A
2 Overview of Presentation IntroductionMethodologyAnticipated Results & ProblemsReferencesIntroduction – Will state the goal of my project and give an introduction to DRASTICMethodology – Will provide a more detailed look at DRASTIC. Will discuss: method development, give examples of it’s application, provide a detailed look at the method itself. Will also discuss the general process I plan to follow for carrying out the project, including constraints and limitations that I will have.Anticipated Results & Problems – will discuss what I hope to end up with, what problems I expect that I may encounter, and how my results can be improved upon.References – A list of sources, primarily from the examples, but the important one is the EPA method document.
4 Introduction My Project DRASTIC DRASTIC Groundwater Vulnerability Map of TennesseeDRASTICWhat is it?Identifies areas where groundwater is susceptible to pollutionWhat are the applications?Guides land development & resource protectionFlexibleUsed at a variety of scalesCan be modified to include or exclude parametersThe goal of my project is to produce a DRASTIC groundwater Vulnerability map of Tennessee. Internet research and conversation with TN Department of Env. Conservation (TDEC) has not revealed any instances where this has been done for TN.DRASTICWhat is it? – Anyone who took GEOG 487 – Environmental Applications of GIS with Ken Corridini probably remembers DRASTIC. It is a method used to identify areas where the groundwater is more or less susceptible to impact from pollution.What are the applications? – Used to guide land development and resource protection.It can be used on a variety of scales, including sites (if they are large enough) such as the Savannah River Site in South Carolina, watersheds such as the Chippewa Creek watershed in OH, and states such as Pennsylvania.It can be modified to include or exclude parameters such as nitrates and pesticides as in the study conducted on the Snake River Basin, ID. It can also serve as the basis for new methods as in the Florida Aquifer Vulnerability Assessment
5 Example DRASTIC MapHere is an example of a DRASTIC Map. The lighter areas are more susceptible to contamination.
7 DRASTIC Overview DRASTIC – methodology guided by EPA Developed by EPA & National Water Well Assoc.600+ page guidance documentLink to Guidance:xtPurpose – Over large areas, used to identify regions where groundwater is more or less susceptible to impact from pollution.The DRASTIC method was developed by the EPA and the National Water Well Association. According to the EPA DRASTIC guidance document (EPA, 1987), DRASTIC is a qualitative method that is intended to be used over large areas as a way to begin to understand which areas are more or less likely to be impacted by contamination from the surface migrating into aquifers.
8 DRASTIC Overview Cont. Overview of DRASTIC Simplified GW vulnerability modelQualitativeProduces a relative-risk scaleApplicable over large areasUsed as a screening toolResults guide land development & resource protectionFor small, specific sites, more detailed assessment neededSimplified model – DRASTIC is a relatively simple model compared to many other vulnerability models. Requires relatively fewer data inputsQualitative – results are qualitative.Qualitative results produce a “relative-risk” scaleApplicable to large areasScreening toolResults can guide general land development & resource protection decisionsFor small areas, more detailed assessment is needed.The DRASTIC method was developed by the EPA and the National Water Well Association as a way to produce a relative-risk scale of potential groundwater vulnerability to pollution that could be applied to a large area, while requiring relatively little data compared to other vulnerability models. According to the EPA DRASTIC guidance document (EPA, 1987), DRASTIC is a qualitative method that is intended to be used over large areas as a way to begin to understand which areas are more or less likely to be impacted by contamination from the surface migrating into aquifers. Due to the relative simplicity of DRASTIC compared to some other vulnerability assessment models, the large scale for which it is intended, and the qualitative nature of the results, DRASTIC should be thought of as a screening tool or as a “coarse-grained” look at aquifer vulnerability modeling that helps guide decisions and focus resources on areas that may require more detailed analyses, whether for land use decisions or environmental protection. Although DRASTIC is useful over large areas and serves as a good first step, ultimately, when making site-specific decisions on small, local areas, additional detailed site-specific hydrogeologic modeling of contamination potential would be considered as an appropriate next step.
9 DRASTIC Method Assumptions DRASTIC Makes Four Assumptions:Contamination is introduced at the ground surfaceContamination is flushed into the groundwater by precipitationContamination has the mobility of waterArea being evaluated is 100-acres or largerIf these assumptions are not met, then DRASTIC is not the appropriate methodologyIn order for DRASTIC to be properly utilized and the results of the DRASTIC analysis to be fully understood, it is necessary to understand the assumptions that the method makes. The four key assumptions are:Contamination is introduced at the ground surfaceContamination is flushed into the groundwater by precipitationContamination has the mobility of waterArea being evaluated is 100 acres or largerIt would be an inappropriate use of the DRASTIC methodology to apply it in situations where these four assumptions are not valid.
10 DRASTIC FactorsSeven hydrogeologic factors used. They form the acronym DRASTIC D – Depth to Water R – Net Recharge A – Aquifer Media S – Soil Media T – Topography I – Impact of Vadose Zone Media C – Hydraulic Conductivity of AquiferTo develop the relative-risk index, DRASTIC utilizes the hydrogeologic factors that most significantly affect movement of contamination from the surface into an aquiferThe seven hydrogeologic factors, which form the acronym “DRASTIC” include:D – Depth to WaterR – Net RechargeA – Aquifer MediaS – Soil MediaT – Topography (slope)I – Impact of Vadose Zone MediaC – Hydraulic Conductivity of aquifer
11 Weights & RatingsSignificance of each factor in contaminant transport variesRelative weight is assigned to each factorScale of 1 to 51 is least important factor5 is most important factorEach factor also has a rating applied according to a category or range of values.The importance of each factor in contaminant transport varies, therefore, each factor is assigned a relative weight on a scale of 1 to 5 (5 being the most significant). Further, each factor is divided into ranges or categories, to which is applied a rating. To develop the DRASTIC index for an area, the rating and weight of each factor are multiplied and the result for each factor is then added.
12 DrDw + RrRw + ArAw + SrSw + TrTw + IrIw + CrCw = Pollution Potential DRASTIC – The EquationOnce ratings and weights have been applied, they are multiplied and addedDRASTIC equation:DrDw + RrRw + ArAw + SrSw + TrTw + IrIw + CrCw = Pollution Potentialr = ratingw = weightResults are symbolized on a map overlaying study areaOnce the analysis has been completed – ratings and weights assigned to each factor and the results summed – the resulting relative-risk index can then be symbolized on a map overlaying the study area, providing a qualitative analysis of the vulnerability to pollution.
13 Methodology - Example Example of how ratings and weights are applied Will use D Factor (Depth to Water) as exampleD receives a weight of 5It is very significant in potential impact to GWBased on actual depth to groundwater, D also receives a rating.As an example of the application of the ratings and weights, consider factor D - Depth to Water. Following the guidelines established in the methodology, the D factor, being important in contaminant movement, receives a weight of 5. However, we also have to consider the actual depth to water.
14 Methodology – Example Cont. If depth to water was 10 ft then D rating would be 9DrDw = 9 x 5 = 45If depth to water was 100 ft, then D rating would be 2DrDw = 2 x 5 = 10This process is repeated for each of the factorsIf the depth to water was 10 feet, then in addition to a weight of 5, D would also receive a rating of 9, producing a combined value of 5 x 9 = 45. If the depth to water was 100 feet, then D would only receive a rating of 2, which would produce a combined value of 5 x 2 = 10. So, the actual values for each factor, such as depth to water, really plays a huge role in the DRASTIC scores.
15 What follows is an example (from my project in GEOG 487) that will give a feel for how the overlay works – how the inputs are combined to arrive at the final DRASTIC index. There won’t be much to say about these slides. I intend to move through them quickly – only a few seconds per slide.elevation
21 This slide just highlights that there are a lot of intermediate steps involved in this analysis.
22 This is the resulting map This is the resulting map. The lighter areas are more susceptible to contamination.
23 Capstone ProcessReview of DRASTIC methodologyIdentify data neededGather dataIdentify Data GapsFill Data Gaps or revise methodologyPerform analysisCreate MapPresent ResultsTo successfully develop the proposed DRASTIC model and complete the capstone project, it will be necessary to develop and follow an overall capstone process, as well as a process specific to the data analysis. The general approach to completing the Capstone project will include the following steps:Review of DRASTIC methodology – this will establish the fundamental methodology for the projectIdentify data needed – required data will be identified in the DRASTIC methodology guidanceGather data – mine data from public sourcesIdentify Data Gaps – this includes data inputs that could not be located in a GIS formatFill Data Gaps or revise methodology – will need to either infer the missing inputs from other available data or will need to revise the methodology, if possible, to exclude the missing inputs.Perform analysis resulting in relative risk indexCreate MapPresent Results, including problems encountered and suggestions for model refinement
24 Data Analysis ProcessOrganize dataRe-project into common coordinate system and datumClip to boundary of TN if necessaryConvert vector data to raster dataGeneralize data where appropriateApply ratings to values and categories in each factor layerApply weights to each input layerSum factorsRelative Risk Index is created and overlain on study areaAn generalized overview of the approach to performing the analyses for the projectGeneralize data where appropriate - for example if there a dozen types of clay represented in the soils data, then it may be appropriate to generalize to a single type for this model
25 Self-Imposed Project Parameters Due to time constraints, need to impose parameters on the analysisUse unmodified version of methodUse existing datasets as much as possibleTo fill datagaps will use the easier of two approaches:Derive missing data from other existing dataUse generalized values in EPA guidanceBecause a project like this could go on for a long long time if you wanted it to, what with searching for better and better data, re-running the analysis, refining the model, and on and on, I felt it was necessary to impose to limitation on myself at the beginning.The primary time constraint is that I want to finish and graduate.I will use unmodified versionI will use existing datasets wherever possible regardless of scale or resolution.Will fill data gaps be the easiest method.In order to successfully complete a DRASTIC analysis of the state within the time constraints of the capstone project, I plan to use the standard, unmodified version of the method as outlined in the EPA guidance. In other words, I will not be adding factors such as pesticides or nitrates. In addition, it will be necessary to utilize existing input data as much as possible even though available data may be of low resolution or small scale. In cases where the required data do not exist, it will be necessary to either infer the input data from other available data or to use the generalized inputs provided in the DRASTIC guidance document. When filling data gaps, where possible, the generalized inputs from the EPA guidance document will be used.
27 Anticipated Results State of TN groundwater vulnerability map Detailed report of methodology and data usedMap will be technically correctConsidered FINAL within context of capstone projectConsidered DRAFT by public and professionals who may use itAt the end of the project, I anticipate that I will have developed a basic groundwater vulnerability map of the state of Tennessee, along with a detailed report of the methodology and data used. I expect that the resulting DRASTIC relative-risk index will be technically correct from the standpoint that the DRASTIC methodology was followed and the spatial analyses were performed correctly. Although I expect the groundwater vulnerability map produced from this project to be technically correct, I also believe that it should be considered to be a DRAFT map by the public and professionals who might use it.
28 Anticipated Problems Low Resolution Data Missing data Anticipate using only small scale dataMissing dataNot all inputs may be availableMay have to infer data or use generalized inputsRoom for improvementAnalysis can be easily re-run with better dataBetter data = better resultsAdditional refinement outside the scope of this capstone projectSo, why do I think my map should be considered a “draft” and have room for improvement?Low Resolution Data: This will be due to the fact that for this project I anticipate only the use of small-scale datasets (1:250,000). The incorporation of more detailed (larger-scale) localized data into the analysis would improve the results.Missing Data: In addition, it may be necessary to fill data gaps by either inferring the missing data from other existing data, or by using the generalized values provided in the methodology guidance. Both methods may introduce inaccuracy into the data.Room for Improvement: Because of low res data and missing data/filling data gaps, the model developed by this project will have room for refinement. The incorporation of more detailed (larger-scale) localized and more accurate data into the analysis would result in a more accurate map of the relative-risk index. In other words, the relative-risk index that results from this project should be considered a first step in developing an accurate and useful groundwater vulnerability model of Tennessee, rather than a definitive final step.
30 Summary Project to produce groundwater vulnerability map of Tennessee Has not been done for TennesseeUse EPA DRASTIC vulnerability methodologyUse small scale, publicly available dataResult will be a first cut at groundwater vulnerability mappingModel will have room for refinementOutside the scope of this project
34 References U.S. EPA DRASTIC Guidance Document United States Environmental Protection Agency (EPA), 1987, DRASTIC: A Standardized System for Evaluating Ground Water Pollution Using Hydrogeologic Settings, EPA/600/ , Robert S. Kerr Environmental Research Laboratory, Ada, OK 74820Examples of the Application of DRASTICArthur, Jonathan D., et al., 2005, Florida Aquifer Vulnerability Assessment (FAVA): Contamination Potential of Florida’s Principal Aquifer Systems, Division of Resource Assessment and Management, Florida Geological SurveyChowdhury, Shafiul, et al, 2003, Comprehensive approach of groundwater resource evaluation: a case study in the Chippewa Creek watershed in Ohio, The Ohio Journal of Science, December 2003Crider, S.S., 1989, A Cursory Application of DRASTIC to the Savannah River Site, WSRC-RP , DE , Division of Engineering Fundamentals, Virginia Polytechnic Institute and State University, Blacksburgh, VA Evans, Barry, et al, 1990, A GIS-Based Approach to Evaluating Regional Groundwater Pollution Potential with DRASTIC, Journal of Soil and Water Conservation, March-April, ppRupert, Michael G., 1999, Improvements to the DRASTIC Ground-Water Vulnerability Mapping Method, USGS Fact Sheet FS , Department of the Interior, US Geological Survey, Denver, CO 80225