The impact of the embankment and the recreational lake on capturing front with drilling wells

Abstract

This paper presents the influence on the levels from the well caption front Gherăeşti-Bacău, located on the right side of the Bistrița River, through the construction, on the right shore, of a 2.25 km long perimetral embankment, and a recreational lake with a surface of 3.18 hectares and average depth of 5.5 m (Figure 1). Through numerical modelling, using the modelling software of Visual Modflow aquifer, the influence on the hydrostatic level from drilled wells was determined, as well as the influence on the phreatic flow through the making of the recreational lake, which captures a part of the underground water. The use of the mathematical model allows the determination of the optimal parameters for an extraction from the aquifer known through classical methods. To achieve the mathematical model the method of filtration resistances was used, which is applied in the case of a sudden curvature of the streamlines (in the proximity of the imperfect permeable/impervious borders: channels, drains, well systems, screens), hence they are applied during pressure/level drops. This method allows the following equalizations: the imperfect wells can be considered as perfect; the lines of perfect/imperfect wells can be considered as perfect trenches (channels) with a flow equal to the sum of all wells; a stratified aquifer (up to 3 layers) can be equivaled with a homogenous one. Aspects regarding the flow were taken into consideration: with a free level or under pressure, the dimensioning of the model, the initial conditions of the aquifer layer, the lithostratigraphic characteristics, homogeneity, anisotropy, the transfer mechanisms in the domain’s interior, the studied hydrogeological structure was schematized, having done a monolayer model. The calibration of the model consists of adjusting, in reasonable conditions, of the domain data (the permeabilities), boundary conditions, so that through the running of the model and obtaining the corresponding piezometric lines and the obtained data will overlap the levels of the existing drillings.