Ground Well (#76) correlates with GDS symbols in Section 26.1 (Geohydrologic Feature; Water Wells). The GDS symbols are quite detailed, and show many types of water wells. If we assume that the HSWG is most interested in portraying operating (not dry or abandoned) wells for towns, homes, and industry, then correlation can be found with symbols 26.1.1; 26.1.6-12; 26.1.15; 26.1.34-39; 26.1.43-48; and 26.1.51.
Reservoir (#80) correlates with GDS symbols in Section 30 (Topographic and Hydrographic Features), specifically symbols 30.2.36 (Reservoir with natural shoreline), 30.2.37 (Dammed reservoir), 30.2.39 (Reservoir, uncovered, with man-made shoreline), and 30.2.40 (Covered water storage reservoir).
The GDS standard includes symbols for water aqueducts and pipelines. Paralleling the suggestion made in item 2.B (above), the GDS suggests that portraying the locations of these features might prove worthwhile, in consideration of their security implications.