this paper presents an analytical model characterizing unsteady groundwater flow in an unconfined aquifer resting on a sloping impervious bed. the aquifer is in contact with a constant water level at one end. the other end is connected to a stream whose level is increasing form an initial level to a final level at a known exponentially decaying function of time. moreover, the aquifer is repleni...

Colloids may have an important role in regulating the structure and function of groundwater ecosystems, and may influence the migration of low solubility contaminants in groundwater. There is, however, a degree of uncertainty about how colloids behave under the variable hydrogeochemical and hydrodynamic conditions that occur during managed aquifer recharge. We used an online monitoring system t...

This study investigates the influence of key factors-mainly recharge rate and degradation half-life--on downward migration of the widely used pesticide mecoprop (MCPP) through a typical clayey till aquitard. The study uses the numerical model FRAC3Dvs, which is a three-dimensional discrete fracture/matrix diffusion (DFMD) numerical transport model. The model was calibrated with laboratory and f...

[1] The subsurface transfer of water from a mountain block to an adjacent basin (mountain block recharge (MBR)) is a commonly invoked mechanism of recharge to intermountain basins. However, MBR estimates are highly uncertain. We present an approach to characterize bulk fluid circulation in a mountain block and thus MBR that utilizes environmental tracers from the basin aquifer. Noble gas rechar...

An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbonmeasurements from 565 wells in 45 networks were used to calculate groundwater r...

One interesting hydrogeological feature of the small (less than 4 km) Almuñécar alluvial aquifer -andalusian mediterranean coast, Spainis related to its seasonal intrusion-extrusion cycles. This is thought to be a consequence of the coarse and clean nature of the sediments and the correspondent high values of hydraulic conductivity (around 500 m/day). The recharge (14 hm/y as an average) comes ...