Aquifer elements interact with land segments, reaches and reservoirs – gaining water from ‘deep percolation’ from land segments, influent streams and seepage from reservoirs, and losing water to down gradient aquifer elements, pumpage, and outflow to streams – Hfam II Scope.
Aquifer elements are well suited for ground water in alluvium in valleys or in alluvial fans where the connection between surface water and groundwater is well defined. Aquifer elements would not be used to represent regional multi-layer groundwater regimes where software capable of greater detail, e. g. MODFLOW, would be used.
Aquifer elements in Hfam II are additional to the ‘perched’ ground water flow path that supplies base or ground water flow in streams. They can be used to track the overall water balance in a watershed where subsurface flow might elude stream gages, avoiding the ‘bottomless pit” in Steven Gorlick’s and David Stonestorm’s diagram of the Stanford Watershed Model IV (this copy was enhanced by Jones in 1997 and Loague in 2000).