Influence of Hydraulic Conductivity and Wellbore Design in the Fate and Transport of Nitrate in Multi-aquifer Systems |
| |
| Authors: | Amanda Mejía Eduardo Cassiraga and Andrés Sahuquillo |
| |
| Institution: | (1) Group of Hydrogeology, Department of Hydraulic and Environmental Engineering, Universitat Polit?cnica de Val?ncia, Camino de Vera s/n, 46022 Valencia, Spain |
| |
| Abstract: | Nitrate concentrations in multi-aquifer systems are heavily affected by the presence of wellbores (active or abandoned) that
are screened in several aquifers. The spatial variability of hydraulic conductivity in the confining layers has also an important
impact on the concentrations. A synthetic three-dimensional flow and transport exercise was carried in a multi-aquifer system
consisting of two aquifers separated by an aquitard in which 100 vertical wellbores had been drilled. To model the wellbores
and the flow and transport connection between aquifers that they may induce, we assign a high vertical hydraulic conductivity
and a low effective porosity to the cell blocks including the wells. With these parameters, a solute will travel quickly from
one aquifer to the other without being stored in the well itself. The wellbores will act as preferential pathways, and the
solute will move quickly between aquifers according to the hydrodynamic conditions. Not considering these preferential pathways
could induce erroneous interpretations of the solute distribution in an aquifer. We also noted that when there are vertical
wellbores that connect aquifers in a multi-aquifer system, low conductivity in the aquitard enhances the flow of solute through
the wellbores. Time-varying pumping rates induce important fluctuations in nitrate concentrations; therefore, any estimate
of the water quality of the aquifer will depend on the moment when the data has been recorded. Consequently, concentration
maps obtained by interpolation of point samples are seldom a good indicator of the chemical status of groundwater bodies;
alternatively, we recommend complementing the usual interpolated maps with numerical models to gain a true understanding of
the spatial distribution of the solute concentration. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
