SYMBOLS FOR USE ON MAPS SHOWING FEATURES OF GROUND WATER.
The symbols used on maps relating to ground water represent the features named below, each of which has been shown in publications already issued.
| Area of absorption or outcrop. Depth to water table. Contours of water table. Fluctuation of water table. Depth to water-bearing formation. Structure contours of water-bearing formation. Area of artesian flow. Head of artesian water. | Area that discharges ground water. Quality of ground water. Area irrigated with ground water. Nonflowing well. Flowing well. Unsuccessful or dry well. Well with pumping plant. Spring. |
The lack of uniformity in the symbols commonly employed to represent these features is due to differences in the number of color on the maps and differences in the scale. Standard colors for the larger features, such as those for areas of artesian flow, areas of absorption, and curves showing depths to water table or to water-bearing formations, can not be fixed, because of considerations of economy in printing. For example, if light green is the standard color to be used for delineating areas irrigated by ground water and no green is used on other parts of the map its use would represent an additional or special printing, whereas a tint of blue, brown, or purple, if any of these colors is used for other features on the map, might be used also for this feature without additional printing. Therefore the general use of any particular color for a water feature seems to be impracticable; but this fact should not preclude the adoption of color standards for use subject to the requirements of economy in publication.
The ordinary symbols for wells are the open circle and the solid circle, or dot. Only in the secondary or specific well symbols does there appear to be lack of uniformity, the choice of secondary symbols being governed either by personal preference or by the requirements for specific distinction.
All symbols should, if possible, suggest the things they represent. Wells are circular and hence the open circle is most used and most appropriate for nonflowing wells. To indicate a flowing well the circle is made solid, denoting that the well is full of water. For an unsuccessful well the most suggestive symbol would be an open circle with a line drawn through it to denote cancellation. It has been suggested that if water features, including wells, are to be printed in blue, unsuccessful wells, or dry holes, be printed in black. A large circle drawn around the symbol for a flowing or nonflowing well will appropriately denote a pumping plant at the well.
The accepted symbol for a spring is a dot with a waved tail representing the direction of flow, if known. This symbol can not be modified without destroying its prime characteristics, but it may be accompanied by a letter indicating the kind of spring. An open circle with a tail might be used on large-scale maps, but it would be out of scale on other maps, whereas the black or blue dot and tail will fit maps of any scale.
The following colors and symbols can most appropriately be used to represent ground-water features. The well and spring symbols can be varied by adding letters if they are necessary to express other data than those indicated in the list below.
General ground-water features.
Area of absorption or outcrop: Flat color used on the map to show the geologic system in which the absorbing formation occurs.