• Merete Dons Hørlück
  • Christian Winde Pedersen
The master project deals with an analysis of the hydrogeological and solute transport parameters, which determine how the flow and solute transport occurs in fractured limestone. The analysis is based on a groundwater protection against nitrate at Aalborg Supply, Water A / S's well field in Drastrup where an effect on the quality of the recovered water, a decade after the protection started, is still not visible. To make the analysis three experiments have been conducted, flow experiments on small, medium, and large, scale, and solute transport experiments on the medium and large scale. For flow experiment on a small scale an average hydraulic conductivity to 5.2 E-3 m/s and a mean total porosity of 0.44 cm^3 pores/cm^3 soil is determined for six intact samples of limestone. From the flow and solute transport experiment at the medium scale a hydraulic conductivity of 2.6 E-5 m/s, an effective porosity of 0.03 cm^3 pores/cm^3 soil is determined, including that the dispersion is small. Based on the measured breakthrough curves for chloride, it is found that chlorine is detained by up to a factor of 11 compared to velocity of the water, caused by the exchange between fractures and matrix. By modeling the measured breakthrough curves with three simplified, it is found that none of the methods describes the transport sufficiently accurate to fit the curves completely. It is deemed that a numerical sorption model is the most useful. The flow and solute transport in a large scale experiment is determined by the modeling of the breakthrough curves. A hydraulic conductivity of 1.1 E-3 m/s, and an effective porosity of 0.014 cm^3 pores / cm^3 soil is determined. On this basis a 3D groundwater model for Drastrup is constructed, from which it is estimated that groundwater protection will ensure that the nitrate concentrations in the aquifer will be below the groundwater criteria 100 to 200 years from 1994.
Publication date8 Jun 2012
Number of pages146
ID: 63636349