Geostatistical hydrogeochemical 3D model for Kłodzko underground water intake area. Part I., Estimation of basic statistics on quality parameters of underground waters

The paper presents the first stage of research on a geostatistical hydrogeochemical 3D model dedicated to the horizontal and vertical spatial and time variation in the topographical, hydrological and quality parameters of underground water in the Kłodzko water intake area. The research covers the period 1977–2012. For this purpose various thematic databases, containing original data on coordinates X, Y (latitude and longitude) and Z (terrain elevation and time – years) and on regionalized variables, i.e., the underground water quality parameters in the Kłodzko water intake area determined for different analytical configurations (22 wells, 14 wells, 14 wells + 3 piezometers), were created. The data were subjected to spatial analyses using statistical methods. The input for the studies was the chemical determination of the quality parameters of underground water samples taken from the wells in the water intake area in different periods of time. Both archival data (acquired in the years 1977–1999, 1977–2011) and the latest data (collected in November 2011 and in January 2012) were analyzed. First, the underground water intake area with 22 wells was investigated. Then in order to assess the current quality of the underground water, 14 wells out of the 22 wells were selected for further chemical analyses and a collection siphon wall was included. Recently, three new piezometers were installed in the water intake area and so new water samples were taken, whereby the databases were supplemented with new chemical determinations. The variation in the topographical parameter (terrain elevation) and in the hydrogeological parameters: water abstraction level Z (with and without the land layout being taken into account) and the depth of occurrence of the water table, was examined. Subsequently, the variation in quality parameters was studied on the basis of data coming from 22 wells, then 14 wells and finally from 14 wells and 3 piezometers. The variation in: Fe, Mn, ammonium ions NH4+, nitrite anion NO3 – and phosphate anion PO4 –3 content values, total organic carbon (TOC) C content, the pH reaction and temperature (°C) of the water was investigated. The basic statistics and distribution histograms of the topographical, hydrogeological and quality parameters (22 wells, 14 wells, 14 wells + 3 piezometers; the years: 1977–1999, 2011, 2011–2012) were estimated and detailed characteristics of the variation in the parameters in the whole underground water intake area over the years were obtained. Generally, the behaviour of the underground water quality parameters has been found to vary in space and time. Thanks to the multidirectional spatial analyses of the variation in the quality parameters in the Kłodzko underground water intake area some regularities in the variation in water quality have been identified.