( 2008 ) expanded these historical schemes to include 12 spheres of discharge of springs, including: (1) springs that emerge in caves, (2) exposure springs, (3) artesian fountains, (4) geysers, (5) gushets, (6) contact hanging gardens, (7) helocrene wet meadows, (8) hillslope springs, (9) hypocrene buried springs, (10) limnocrene surficial lentic pools, (11) mound forms, and (12) rheocrene lotic channel floors (Figs.  1 and 2 ; Table  1 ).

Cave springs are those that emerge entirely within a cave environment and are not directly connected to surface flow (Figs.  1 a and 2 a).

( 2008 ; Figs.  1 b and 2 b).

Fountain springs are cool-water artesian springs that are forced above the land surface by stratigraphic head-driven pressure or CO ₂ (e.g., Crystal Geyser; Glennon and Pfaff 2005 ; Figs.  1 c and 2 c).

Geysers are globally rare, geothermal springs that emerge explosively and usually erratically (Figs.  1 d and 2 d).

( 2008 ; Figs.  1 e and 2 e).

Hanging gardens are complex, multi-habitat springs that emerge along geologic contacts and seep, drip, or pour onto underlying walls (Figs.  1 f and 2 f).

Helocrene springs usually emerge in a diffuse fashion in cienega (marshy, wet meadow) settings (Figs.  1 g and 2 g).

Hillslope springs emerge from confined or unconfined aquifers on non-vertical hillslopes at 30–60° slopes, and usually have indistinct or multiple sources (Figs.  1 h and 2 h).

Hypocrene springs are springs in which groundwater levels come near, but do not reach the surface (Figs.  1 i and 2 i).

Limnocrene springs occur where discharge from confined or unconfined aquifers emerge as one or more lentic pools (Figs.  1 j and 2 j).

Mound-form springs emerge from (usually carbonate) precipitate mounds or peat mounds (Figs.  1 k and 2 k).

The term rheocrene was first coined by Bornhauser ( 1913 ) to describe springs where discharge emerges as flowing streams (Figs.  1 l and 2 l).