Table 2.

Translation of the key to Oberleutnant Walther Klüpfel's 1942 ‘First draft of a water map for the island of Jersey’, with colour or symbol if discernable on Figure 11

Red dots: Sandy porous deposits of the coastal zone and embayments. Dunes. Water obtainable everywhere by means of shallow wells.
Purple, mostly in NW: Shallow aquifer in weathered granite, 3–8 m below land surface. Water obtainable everywhere by means of shallow wells. Satisfactory abstraction possible throughout the whole year in shallow basin areas.
Horizontal lines: Shallow aquifer above shale, [water obtainable] less regularly. (Still to be ascertained precisely.)
Vertical lines: Area of quartz porphyry, near-surface zone arid. Shallow wells locally in porous zones. A limited amount of water can be made available by means of deep wells.
Crossed horizontal and vertical lining: Subsurface water basin inferred.
Red: Porphyry region. Probably most barren at the outer border (especially in the west and south) because of intrusion into shale.
Probably somewhat better at the inner border. Occasional deep wells.
Deep wells are practicable in the valley bottoms of the quartz porphyry area.
Grey, to NE: Tuff region, with inclusions of ‘fluidal-’ and felsite-porphyry. Shallow wells locally in porous zones. Occasional deep wells, with little water. An unfavourable region [for groundwater development].
Yellow, NE corner only: Conglomerate region. Lacks a shallow aquifer. Jointing makes the rock permeable, but water is difficult to abstract. Occasional deep wells, with little water. An unfavourable region [for groundwater development].
Pale area outlined in red, mostly to NW: Granite region. Mostly barren. Water circulates in ill-defined fracture zones.
Sporadically, it is inferred that basinal areas at the southern boundary of the shales contain water in fractures. (Strong spring in the 30-m-deep Handrois quarry.)
Yellow. Shale region, barren. Exploratory boreholes have so far been completely unsuccessful. Sporadically slightly water-bearing at shallow depth (up to 35 m deep) in fracture zones, but dry at depth.
Felsite boundary zone cut by valleys and without significant catchment area; dry.
Triangle: Point suitable for a major water source at the White Tower, St. Catherine's Bay.
Crescent: Place probably favourable for the construction of underground reservoirs or galleries.
Circular spot: Successful borings to date. See plan for yield.