Aquifers in carbonate karst rocks are characterized by a known extreme heterogeneity of hydrogeological parameters both in the plan and in the section. This paper presents the results of the study of the distribution of permeability and capacity of the Podolsko-Machkovsky limestone aquifer in the scale of the first meters. On the basis of theoretical developments, supported by many years of field experimental research, it is shown that the main elements of the aquifer structure are thin permeable zones formed as a result of the karstification on the contacts of limestone layers of different lithological composition (bedrocks). The zones do not have measurable thickness and are characterized by individual transmissivities and specific capacities varying at distances of about a meter. The zones are separated by relatively low-permeability layers of unkarsted limestone. The methods of flowmetry in the static and dynamic variants, resistivimetry with details in determining the flow rate are used to identify the thin permeable zones. Layer and zone contacts are performed using electrical logging. Changes in the horizon transmissivity and the specific capacity of the zones in the cluster of 7 wells on an area of about 40 m2 with distances between adjacent wells of 3 m, was determined by cross-wells pumping tests with the recording of pressures and temperatures. All applied methods are modified to solve the presented problems. Even in such an area the neighboring wells show the difference of the aquifer conductivity almost one and a half times. Specific capacities of one thin zone vary by an order of magnitude. The asymmetry of the determined parameters at changing the roles of the experimental and observation wells has been revealed. The results allow us to take a new look at the problem of accuracy of the initial information for hydrogeological modeling — the studied area corresponds to the usual block of the model.
Diffusive groundwater pollution caused by agricultural and atmospheric inputs is a pressing issue in environmental management worldwide. Various researchers have studied nitrate contamination since the substantial increase of nitrogen fertilization in agriculture starting in the second half of the 20th century. This study addresses large scale reactive solute transport in typical landscapes and aquifers exemplified by geological analogues of southwestern Germany.. Fate of nitrate and other solutes (e.g. agricultural nitrate, ammonium, natural sulfate and dissolved organic carbon) was studied in a typical small river floodplain. Reactive transport model of Ammer river floodplain shows that agriculture nitrate is reduced rapidly in the Ammer floodplain sediments. However, there is a potential for geogenic production of ammonium in sediment layers high in organic carbon and peat, which might be a major source of nitrate in the drains. Part of the nitrate in drains and creeks in the Ammer valley thus could be of geogenic origin. Such findings are relevant for regional land and water quality management.
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