Karst groundwater vulnerability mapping: application of a new method in the Swabian Alb, Germany

Groundwater from karst aquifers is an important drinking water resource, which is, however, particularly vulnerable to contamination. Karst aquifers consequently need special protection. This paper discusses the concept of groundwater vulnerability mapping and the special characteristics of karst aquifers that are relevant in this context. On this basis, a new method of groundwater vulnerability mapping is proposed—the PI method. It can be applied for all types of aquifers, but provides special tools for karst. Vulnerability is assessed as the product of two factors: protective cover (P) and infiltration conditions (I). The method was first applied and compared with two other methods (EPIK and the German method) in a test site in the Swabian Alb, Germany. The results obtained with the different methods are discussed and an outlook on the role of vulnerability maps within an overall groundwater protections scheme is give

Fold structure and underground drainage pattern in the alpine karst system Hochifen-Gottesacker

Abstract.: This paper summarises seven years of hydrogeological research in the alpine karst system Hochifen-Gottesacker (Germany/Austria). Geologically, the site belongs to the Helvetic nappes and consists of Cretaceous sedimentary rocks. The Schrattenkalk limestone forms a relatively thin karst aquifer above or between thick marl aquicludes, forcing groundwater to flow parallel to the strata. The limestone is intensively cut by faults and fractures favouring karstification. The fault offsets are relatively small, so that their influence on the large-scale groundwater flow paths is limited. The site is thus ideal to study the influence of fold structures on the drainage pattern. Multi-tracer tests with a total of 16 injections demonstrated that troughs of plunging synclines form the main underground flow paths, while crests of anticlines act as local groundwater divides in the higher karst zones where the base of the aquifer is above the level of the surrounding valleys. In an adjacent valley that receives inflow from several synclines, tracer tests confirmed a major underground drainage system running across the folds. An axial culmination in the area is part of the continental water divide Rhine-Danube; an axial depression acts as a zone of confluenc

A new quantitative interpretation of the long-tail and plateau-like breakthrough curves from tracer tests in the artesian karst aquifer of Stuttgart, Germany

In 1998 and 1999, two multi-tracer experiments were conducted in the artesian karst aquifer of the mineral springs of Stuttgart, Germany. The breakthrough curves (BTCs) monitored at the springs showed very long tails or developed plateau-like concentration levels for more than 200 days. Initially, this observation was qualitatively explained by exchange between cavities with stagnant water and the active conduits. Since then, a new analytical solution for tracer transport in karst aquifers has become available, the "two-region non-equilibrium model” (2RNE), which assumes the presence of mobile and immobile fluid regions, and mass transfer between these two regions. The experiments were thus revisited, and it was possible to provide a more quantitative explanation of the observed behaviour. The new model simulated all BTCs very well, thus confirming the earlier qualitative explanation. The prolonged BTCs can be attributed to intermediate storage in cavities containing quasi-immobile groundwater, and slow release into active fractures and conduits. The results also demonstrate that karst aquifers are not always fast-flushing systems, but contaminants can sometimes remain in immobile fluid regions for long period

A simplified methodology for mapping groundwater vulnerability and contamination risk, and its first application in a tropical karst area, Vietnam

A simplified methodology for mapping groundwater vulnerability and contamination risk is proposed, and the first application of the methodology, in a mountainous tropical karst area, is presented. The test site is the Tam Duong area, one of the poorest and remotest regions in northern Vietnam. The methodology requires a minimum of input data, which makes it particularly useful for developing countries. Vulnerability is assessed on the basis of two factors, which take into account the duality of recharge processes in karst aquifer systems: the overlying layers (O) and the concentration of flow (C). The risk map is obtained by putting together the vulnerability map and a simplified hazard assessment. The resulting maps provide a basis for groundwater protection zoning and land-use planning. Tracer tests and microbiological data confirmed the vulnerability and risk assessment in the test sit

Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam

The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment area

Proposed Methodology of Vulnerability and Contamination Risk Mapping for the Protection of Karst Aquifers in Slovenia

On the basis of work accomplished by the European COST Action 620, a comprehensive approach to groundwater vulnerability and contamination risk assessment is proposed, taking into account the special characteristics of Slovene karst aquifer systems. The Slovene Approach is consistent with national environmental legislation and enables comparison across European countries. The method integrates temporal hydrological variability in the concept of groundwater vulnerability and offers a new possibility to combine surface and groundwater source and resource protection, which required the development of a new K factor (karst groundwater flow within the saturated zone). The risk analysis considers intrinsic vulnerability, contamination hazards and the importance of the source or resource. It has been first applied to the Podstenjšek springs catchment in southwestern Slovenia and validated by means of two multi-tracer tests with a total of six injection points. The resulting vulnerability, hazard and risk maps are plausible, and the validation confirmed the vulnerability assessment at the representative sites that were selected for tracer injection. The maps provide improved source protection zones and make it possible to identify land mismanagement and to propose better practices for future planning