Evaluating the effectiveness of a fixed wellhead delineation: Regional case study, 2006, Hodgson J. Y. S. , Stoll J. R. , Stoll R. C. ,

The 1996 Safe Drinking Water Act amendments mandated that every state must determine the hydrogeologic origin of each public drinking water system and assess the degree to which each system may be adversely affected by potential sources of contamination. Wisconsin delineated and assessed one specific class of systems, transient noncommunity drinking water wells, with the least stringent standards of all governed system types. This study evaluates the effectiveness of Wisconsin's arbitrarily fixed radius approach used in determining susceptibility to potential contamination from 1,872 transient noncommunity ground water wells. Nearly 28 percent of the wells with contaminated water did not have any recorded potential sources of contamination within the delineation radii. Additionally, regression models derived from potential contaminant inventories within the delineation radii could not accurately predict actual incidences of water contamination. Differences between observed and expected frequencies of contamination further suggest that some transient noncommunity systems should probably be delineated with larger and more sophisticated methods that would account for varying geology and contaminant susceptibility. The majority of contamination cases without recorded potential sources of contamination within the delineation radii were in a karst area. Subsequently, the arbitrarily fixed radius delineation method should not be used in areas with karst aquifers

Hydrogeological uncertainties in delineation of leakage at karst dam sites, the Zagros Region, Iran, 2007, Mohammadi Z. And Raeisi E.

Leakage from dam reservoirs has been reported in different karst regions of the world. Water leakage occurs through the karst features directly or indirectly. The estimation of leakage locations, path(s), and quantity are subject to error due to uncertainties in the non-homogenous nature of a karst formation, method of study, and limited investigation due to time and cost factors. The conventional approaches for study on the karst development are local boring at the dam site and geological mapping. In this paper, uncertainties associated with conventional hydrogeological approaches are addressed from both qualitative and quantitative points of view. No major solution cavities were observed in boreholes and galleries of some dam sites in the Zagros Region, Iran, but huge karst conduits were discovered during the drilling of a diversion tunnel. This inconsistency is due to the point character of boreholes and the inherent nonhomogeneity of karst. The results of dye tracing tests in boreholes may be significantly affected by location of the injection and sampling points, as tests executed at the Saymareh and Tangab Dam sites in the Zagros Region, Iran show. The quantitative uncertainty of leakage is analyzed for diffuse and conduit flow systems for cases with and without any grout curtain, under the combined effect of input uncertainties at the Tangab Dam site, southern Iran. Assuming a diffuse flow system, the mean leakage at 95% confidence interval for both strategies is estimated at less than 5% of the mean annual discharge of the river. Accordingly, the dam can be constructed without the necessity of a grout curtain. However, assuming a conduit flow system, the results reveal a significant uncertainty. A small diameter conduit can convey significant amounts of water under high reservoir pressure heads. The leakage of a 4 m diameter conduit (cross section area of 12.5 m2) is 163 times more than the leakage of 0.5 m diameter conduit (cross sectional area of 0.2 m2) while the cross sectional area ratio is 60. The uncertainty may be decreased if a detailed study is carried out on the stratigraphic and tectonic settings, karst hydrogeology, geomorphology, speleogenesis, and by performing several dye tracing tests, especially outside the proposed grout curtain area.

The protection of karst waters. A comprehensive Slovene Approach to vulnerability and contamination risk mapping, 2007, Nataš, A Ravbar

A general approach for karst water vulnerability and contamination risk assessment has been proposed, taking into account the special characteristics of Slovene karst landscapes, suiting Slovene environmental legislation and enabling comparison across European countries. The so-called Slovene Approach has been developed on the basis of work accomplished by the European COST Action 620. It incorporates the strongly modified COP method for intrinsic vulnerability assessment by integrating temporal hydrological variability, offering a new possibility to combine surface and groundwater protection, as well as by adapting it to source vulnerability mapping. The methodology provides also comprehensive risk analyses based on the intrinsic vulnerability, hazard and (re)source importance assessments. The proposed Slovene Approach has been first applied to the Podstenjšek water source catchment. Different other methods have been applied (EPIK, PI, COP, Simplified method) and compared. For the catchment area delineation, application of different vulnerability and risk methods a holistic research of the test site has been done by means of tracer tests, detail structural-lithological and geomorphological mapping, electrical resistivity imaging, as well as detail hazard mapping. Continuous monitoring of the springs? physico-chemical characteristics has been performed for the hydrograph analyses, water balance calculation and aquifer behaviour comprehension. The resulting Slovene Approach intrinsic vulnerability, hazard and risk maps are justified and validation with tracer tests has proved the method to give plausible results. The resulting maps provide improved source protection zones determination and identification of land mismanagement, as well as reorganisation and better practices for future planning.

GROUNDWATER FLOW IN CRYSTALLINE CARBONATES (JESENIKY MTS., CZECH REP.): USING STREAM THERMOMETRY AND GROUNDWATER BALANCE FOR CATCHMENT DELINEATION, 2008, Kukač, Ka J. , Altová, V. , Bruthans J. , Zeman O.

Strips of metamorphosed carbonate rocks in a contact-karst area in the Jeseniky Mts, Czech Republic, act as aquifers, draining broad areas of crystalline rocks, mostly phyllites. Significant groundwater resources that are partly used as a water supply are in carbonate rocks. Detailed temperature and conductivity measurements coupled with discharge measurements along all streams in the area demonstrate a relatively quick method to locate virtually all important groundwater outflows from carbonates. Discharge measurements of streams crossing carbonate strips enabled us to locate and quantify the capacity of ponors and losing parts of streams in various water stages. Thanks to a detailed knowledge of losing and gaining parts of streams, we were able to select appropriate profiles to separate catchments with differing hydrologic balances (balanced, gaining, losing). Flow directions in carbonates and recharge and discharge areas were delineated by comparing the specific discharges of individual catchments. Resulting flow directions agree with tracer tests in the area. Our outlined approach can be used in many other areas to locate hidden inflows into streams and to estimate flow between individual small catchments, and it may partly compensate for tracer tests as it allows flow directions to be estimated from hydrological balance and rock geometry.

The Dead Sea sinkhole hazard: Geophysical assessment of salt dissolution and collapse, 2011, Frumkin Amos, Ezersky Michael, Alzoubi Abdallah, Akkawi Emad, Abueladas Abdelrahman

A geophysical approach is presented for analyzing processes of subsurface salt dissolution and associated sinkhole hazard along the Dead Sea. The implemented methods include Seismic Refraction (SRFR), Transient Electromagnetic Method (TEM), Electric Resistivity Tomography (ERT), and Ground Penetration Radar (GPR). The combination of these methods allows the delineation of the salt layer boundaries, estimating its porosity distribution, finding cavities within the salt layer, and identifying deformations in the overlying sediments. This approach is shown to be useful for anticipating the occurrence of specific sinkholes, as demonstrated on both shores of the Dead Sea. These sinkholes are observed mainly along the edge of a salt layer deposited during the latest Pleistocene, when Lake Lisan receded to later become the Dead Sea. This salt layer is dissolved by aggressive water flowing from adjacent and underlying aquifers which drain to the Dead Sea. Sinkhole formation is accelerating today due to the rapid fall of the Dead Sea levels during the last 30 years, caused by anthropogenic use of its water.

Integrating geomorphological mapping, trenching, InSAR and GPR for the identification and characterization of sinkholes: A review and application in the mantled evaporite karst of the Ebro Valley (NE Spain), 2011, Gutié, Rrez Francisco, Galve Jorge Pedro, Lucha Pedro, Castañ, Eda Carmen, Bonachea Jaime, Guerrero Jesú, S

This contribution illustrates the advantages of integrating conventional geomorphological methods with InSAR, ground penetrating radar and trenching for sinkhole mapping and characterization in a mantled evaporite karst area, where a significant proportion of the karstic depressions have been obliterated by artificial fills. The main practical aim of the investigation was to elucidate whether buried sinkholes overlap the areas planned for the construction of buildings and services, in order to apply a preventive planning strategy. Old aerial photographs and detailed topographic maps were the most useful sources of information for the identification of sinkholes and helped to obtain information on their chronology, either a minimum age or bracketing dates. The InSAR technique provided subsidence rate values ranging from 4.4 to 17.3 mm/yr consistent with the spatial distribution of the mapped sinkholes. This quantitative deformation data helped corroborating independently the existence of active buried sinkholes and improving the delineation of their limits. The GPR profiles contributed to the precise location of sinkhole edges, provided information on the geometry of buried sinkholes and deformation structures and helped to site trenches and to rule out the existence of sinkholes in particular areas. The main input derived from the trenches includes: (1) Confirming or ruling out anomalies of the GPR profiles attributable to subsidence. (2) Precise location of the edge of some filled sinkholes. (3) Information on subsidence mechanisms recorded by various deformation structures and cumulative subsidence magnitude. (4) Calculating minimum long-term subsidence rates using radiocarbon dates obtained from deformed sinkhole deposits. (5) Unequivocal evidence of active subsidence in areas assigned for the construction of buildings

Using Geographic Information System to Identify Cave Levels and Discern the Speleogenesis of the Carter Caves Karst Area, Kentucky, 2011, Peterson E. , Dogwiler T. , Harlan L.

Cave level delineation often yields important insight into the speleogenetic history of a karst system. Various workers in the Mammoth Cave System (MCS) and in the caves of the Cumberland Plateau Karst (CPK) have linked cave level development in those karst systems with the Pleistocene evolution of the Ohio River. This research has shown that speleogenesis was closely related to the base level changes driven by changes in global climate. The Carter Caves Karst (CCK) in northeastern Kentucky has been poorly studied relative to the MCS to the west and the CPK karst to the east. Previously, no attempt had been made to delineate speleogenetic levels in the CCK and relate them to the evolution of the Ohio River. In an attempt to understand cave level development in CCK we compiled cave entrance elevations and locations. The CCK system is a fluviokarst typical of many karst systems formed in the Paleozoic carbonates of the temperate mid-continent of North America. The CCK discharges into Tygarts Creek, which ultimately flows north to join the Ohio River. The lithostratigraphic context of the karst is the Mississippian Age carbonates of the Slade Formation. Karst development is influenced by both bedding and structural controls. We hypothesize that cave level development is controlled by base level changes in the Ohio River, similar to the relationships documented in MCS and the karst of the Cumberland Plateau The location and elevation of cave entrances in the CCK was analyzed using a GIS and digital elevation models (DEMs). Our analysis segregated the cave entrances into four distinct elevation bands that we are interpreting as distinct cave levels. The four cave levels have mean elevations (relative to sea level) of 228 m (L1), 242 m (L2), 261 m (L3), and 276 m (L4). The highest level—L4—has an average elevation 72 m above the modern surface stream channel. The lowest level—L1—is an average of 24 m above the modern base level stream, Tygarts Creek. The simplest model for interpreting the cave levels is as a response to an incremental incision of the surface streams in the area and concomitant adjustment of the water table elevation. The number of levels we have identified in the CCK area is consistent with the number delineated in the MCS and CPK. We suggest that this points toward the climatically-driven evolution of the Ohio River drainage as controlling the speleogenesis of the CCK area 

Delineating Protection Areas for Caves Using Contamination Vulnerability Mapping Techniques: The Case of Herrer�as Cave, Asturias, Spain, 2012, Mar�n A. I. , Andrea B. , Jim�nezs�nchez M. , Dominguezcuesta M. J. , Mel�ndezasensio

 

Diverse approaches are adopted for cave protection. One approach is delineating protection areas with regard to their vulnerability to contamination. This paper reports the main results obtained from the delineation of a protection zone for Herrerı´as Cave, declared of Cultural Interest by the Asturias Regional Government, based on assessing its vulnerability to contamination. The cave is situated in a complex karst hydrogeologic environment in which groundwater flows from southwest to northeast, following the bedrock structure. A stream flows inside the cave, emerging in a spring located to the northeast of the system. Karst recharge occurs by direct infiltration of rainfall over limestone outcrops, concentrated infiltration of surface runoff in the watershed draining the cave, and deferred infiltration of water from alluvial beds drained by influent streams. The soil and vegetation covers are natural in the majority of the test site, but land uses in the watershed, including scattered farming, stock breeding, quarrying, and tourist use, are changing the natural characteristics and increasing the cave’s vulnerability to contamination. The procedure followed for delineating protection zones is based on the method COP+K that is specifically designed for vulnerability mapping of groundwater springs in carbonate aquifers. To cover the hydrological basin included in the cave’s catchment area, the protection zones established includes two different areas, the hydrogeological catchment basin and adjacent land that contributes runoff. Different degrees of protection in the zones have been proposed to make human activity compatible with conservation of the cave, and our results show remarkable differences from the protection zone previously proposed for the same area.

KARSYS: a pragmatic approach to karst hydrogeological system conceptualisation. Assessment of groundwater reserves and resources in Switzerland, 2013, Jeannin P. Y. , Eichenberger U. , Sinreich M. , Vouillamoz J. , Malard A. , Weber E.

An approach is presented for the hydrogeological conceptualisation of karst systems. The KARSYS approach helps hydrogeologists working in karst regions to address in a pragmatic and efficient way the three following questions. (1) Where does the water of a karst spring come from? (2) Through which underground routes does it flow? (3) What are the groundwater reserves and where are they? It is based on a three dimensional model of the carbonate aquifer geometry (3D geological model) coupled to a series of simple fundamental principles of karst hydraulics. This provides, within a limited effort, a consistent hydrogeological conceptual model of karst flow systems within any investigation area. The level of detail can be adjusted according to the targeted degree of confidence. Two examples of its application are presented; the approach was first applied with a low level of detail on a national scale in order to assess the groundwater reserves in karst aquifers in Switzerland, suggesting a groundwater volume of 120 km3. On a regional scale, it was applied with a higher level of detail to some selected karst systems in order to assess their hydropower potential. The KARSYS approach may provide very useful information for water management improvement in karst regions (vulnerability assessment, impact assessment, water supply, flood hazards, landslides, etc.). It leads, in a very cost-effective manner, to a new and highly didactic representation of karst systems as well as to new concepts concerning the delineation of catchment areas in karst regions.

AN EVALUATION OF AUTOMATED GIS TOOLS FOR DELINEATING KARST SINKHOLES AND CLOSED DEPRESSIONS FROM 1-METER LIDAR-DERIVED DIGITAL ELEVATION DATA, 2013, Doctor D. H. , Young J. A.

LiDAR (Light Detection and Ranging) surveys of karst terrains provide high-resolution digital elevation models (DEMs) that are particularly useful for mapping sinkholes. In this study, we used automated processing tools within ArcGIS (v. 10.0) operating on a 1.0 m resolution LiDAR DEM in order to delineate sinkholes and closed depressions in the Boyce 7.5 minute quadrangle located in the northern Shenandoah Valley of Virginia. The results derived from the use of the automated tools were then compared with depressions manually delineated by a geologist. Manual delineation of closed depressions was conducted using a combination of 1.0 m DEM hillshade, slopeshade, aerial imagery, and Topographic Position Index (TPI) rasters. The most effective means of visualizing depressions in the GIS was using an overlay of the partially transparent TPI raster atop the slopeshade raster at 1.0 m resolution. Manually identified depressions were subsequently checked using aerial imagery to screen for false positives, and targeted ground-truthing was undertaken in the field. The automated tools that were utilized include the routines in ArcHydro Tools (v. 2.0) for prescreening, evaluating, and selecting sinks and depressions as well as thresholding, grouping, and assessing depressions from the TPI raster. Results showed that the automated delineation of sinks and depressions within the ArcHydro tools was highly dependent upon pre-conditioning of the DEM to produce “hydrologically correct” surface flow routes. Using stream vectors obtained from the National Hydrologic Dataset alone to condition the flow routing was not sufficient to produce a suitable drainage network, and numerous artificial depressions were generated where roads, railways, or other manmade structures acted as flow barriers in the elevation model. Additional conditioning of the DEM with drainage paths across these barriers was required prior to automated 2delineation of sinks and depressions. In regions where the DEM had been properly conditioned, the tools for automated delineation performed reasonably well as compared to the manually delineated depressions, but generally overestimated the number of depressions thus necessitating manual filtering of the final results. Results from the TPI thresholding analysis were not dependent on DEM pre-conditioning, but the ability to extract meaningful depressions depended on careful assessment of analysis scale and TPI thresholding.

DELINEATION AND CLASSIFICATION OF KARST DEPRESSIONS USING LIDAR: FORT HOOD MILITARY INSTALLATION, TEXAS, 2013, Shaw Faulkner M. G. , Stafford K. W. , Bryant A. W.

The Fort Hood Military Installation is a karst landscape characterized by Cretaceous-age limestone plateaus and canyons in Bell and Coryell Counties, Texas. The area is located in the Lampasas Cut Plain region of the Edwards Plateau and is stratigraphically defined by exposures of the Fredericksburg Group. Spatial interpolation of 105 km2 of the Fort Hood Military Installation provided depression data that were delineated and classified using geoanalytical methods. Most of the karst features within the study area are predominantly surficial expressions of collapse features, creating windows into karst conduits with surficial exposures of epikarst spatially limited.The increasing capabilities of GIS (Geographic Information Systems) and accuracy of geographically referenced data has provided the basis for more detailed terrain analysis and modeling. Research on terrain-related surface features is highly dependent on terrain data collection and the generation of digital models. Traditional methods such as field surveying can yield accurate results; however, they are limited by time and physical constraints. Within the study area, dense vegetation and military land use preclude extensive traditional karst survey inventories. Airborne Light Detection and Ranging (LiDAR) provides an alternative for high-density and high-accuracy three-dimensional terrain point data collection. The availability of high density data makes it possible to represent terrain in great detail; however, high density data significantly increases data volume, which can impose challenges with respect to data storage, processing, and manipulation. Although LiDAR analysis can be a powerful tool, filter mechanisms must be employed to remove major natural and anthropogenic terrain modifications resulting from military use, road building and maintenance, and the natural influence of water bodies throughout the study area.

AUTOMATIC DETECTION AND DELINEATION OFKARST TERRAIN DEPRESSIONSAND ITSAPPLICATION IN GEOMORPHOLOGICAL MAPPING AND MORPHOMETRIC ANALySIS, 2013, PardoigÚzquiza E. , DurÁn J. J. , Dowd P. A.

Digital elevation models (DEM) are digital representations of topography that are especially suitable for numerical terrain analysis in earth sciences and engineering. One of the main quantitative uses of DEM is the automatic delineation of flow networks and watersheds in hydrology and geomorphology. In these applications (using both low­resolution and precision DEM) depressions hinder the inference of pathways and a lot of work has been done in designing algorithms that remove them so as to generate depression­free digital elevation models with no interruptions to flow. There are, however, geomorphological environments, such as karst terrains, in which depressions are singular elements, on scales ranging from centimetres to kilo­metres, which are of intrinsic interest. The detection of these depressions is of significant interest in geomorphologic map­ping because the development of large depressions is normal in karst terrains: potholes, blind valleys, dolines, uvalas and poljes. The smallest depressions that can be detected depend on the spatial resolution (pixel size) of the DEM. For example, depressions from centimetres to a few metres, such as some types of karren, cannot be detected if the raster digital eleva­tion model has a spatial resolution greater than, say, 5 m (i.e., square 5m pixel). In this work we describe a method for the au­tomatic detection and delineation of terrain depressions. First, we apply a very efficient algorithm to remove pits from the DEM. The terrain depressions are then obtained by subtract­ing the depression­free DEM from the original DEM. The final product is a digital map of depressions that facilitates the cal culation of morphometric features such as the geometry of the depressions, the mean depth of the depressions, the density of depressions across the study area and the relationship between depressions and other variables such as altitude. The method is illustrated by applying it to data from the Sierra de las Nieves karst massif in the province of Málaga in Southern Spain. This is a carbonate aquifer that is drained by three main springs and in which the depressions play an important role in the recharge of the aquifer. A doline density map, produced from a map of 324 detected dolines/uvalas, identifies three main recharge areas of the three springs. Other morphometric results related to the size and direction of the dolines are also presented. Finally the dolines can be incorporated into a geomorphology map.

Interpretation of hydrogeological functioning of a high karst plateau using the KARSYS approach: the case of Trnovsko-Banjška planota (Slovenia), 2013, Turk Janez, Malard Arnauld, Jeannin Pierreyves, Vouillamoz Jonathan, Masini Jean, Petrič Metka, Gabrovšek Franci, Ravbar Nataša, Slabe Tadej

The high karst plateau of Trnovsko­Banjška planota is one of the most important reservoirs of karst water in Slovenia. Almost all important karst springs in this area are captured for water supply. A sustainable management of this source of groundwater is of strategic importance, not only as drinking water supply but also for the economy. For these reasons, many hydrogeological monitoring studies have been carried out over the last decades. However, no consistent regional overview of the hydrogeological functioning of Trnovsko­Banjška planota was available and we decided to study this area with more direct approach based on 3D geological and hydrogeological models. The so called KARSyS approach was developed in Switzerland and applied primarily to characterize groundwater reserves within a karst massif, and to sketch the main flow­paths carrying groundwater from recharge areas to the respective springs. The delineation of spring catchment areas in karst regions was better defined and interactions between catchments were interpreted. These results can be used to improve the management of karst waters in the studied area.