Recharge and aquifer response: Northern Guam Lens Aquifer, Guam, Mariana Islands

Process‐based Modelling of Syn‐depositional Diagenesis

“…High permeability conduits permit rapid transmission of calcite--undersaturated recharge waters to the water table, even with a thick vadose zone (Jocson et al, 2002;Whitaker et al, 2006). This effect is not shown in the simulations of Xiao and Jones (Figure 3.3) which assume flow through an equivalent porous media.…”

Temporal variability in chemical cycling of the subterranean estuary and associated chemical loading to the coastal ocean

“…Thus, the lagoon [Ba] is expected to be inversely related to groundwater discharge, as opposed to the other two sites (Yucatan and North Carolina) where groundwater discharge enriched the coastal ocean [Ba] over offshore values. In addition, precipitation is seasonal, with most rainfall occurring July through November (Jucson et al, 2002), when temperature is high. Thus a low Ba/Ca ratio is expected in corals during the summer due to both the temperature dependence of KBa and to the dilution of lagoon [Ba] with terrestrial groundwater discharge.…”

Simulations of freshwater lens recharge and salt/freshwater interfaces using the HYDRUS and SWI2 packages for MODFLOW

“…In particular, in view of possible climate change, increased water demands and sea level rise, the development of freshwater lenses supplied with infiltrated rainwater on top of saline aquifers is a subject of intense research (e.g., Werner et al, 2013). A large number of contributions have focused on freshwater lenses in deltaic regions, as well as on islands, peninsulas, or sandbars located in tropical, arid, and temperate climatic zones (e.g., Comte et al, 2014;Contractor and Jenson, 2000;Chang et al, 2016;De Louw et al, 2011;Eeman et al, 2017;Holding and Allen, 2015;Houben and Post, 2016;Illangasekare et al, 2006;Jocson et al, 2002;Mahmoodzadeh et al, 2014;Sadurski et al, 1987;Sinclair et al, 2016;Stuyfzand, 2016;Sulzbacher et al, 2012).…”

“…Thus, recharge is inherently variable in space and time and this variability may have a significant influence on freshwater-saltwater dynamics in shallow coastal aquifers (Mollema and Antonelli, 2013;Trglavcnik et al, 2016;Vandenbohede et al, 2014). Other studies highlighted the importance of such factors as water uptake by tree roots (Comte et al, 2014) or hydraulic properties and water storage in the vadose zone (Contractor and Jenson, 2000;Jocson et al, 2002). There is thus a need to include seasonal fluctuations of recharge in groundwater models for coastal aquifers (Eeman et al, 2012;Mollema and Antonellini, 2013;Oude Essink et al, 2010) and to integrate vadose zone processes more fully into groundwater models.…”