Groundwater mapping is the systematic examination of an area for groundwater information. A knowledge of groundwater conditions in an area is useful to hydrogeologists, groundwater hydrologists, geologists, civil engineers, agriculturists, foresters and soil scientists. This report described information obtained only from naturally occurring surficial phenomena studied in moderate detail over a restricted area. This method of determining groundwater conditions is judged to be most valuable in areas where no sources of groundwater information exist, and where surficial phenomena resulting from groundwater can be differentiated from those resulting from surface water.

Where the water table is a subdued replica of the topography, movement of groundwater is the result of topographic relief, modified by inhomogeneities in the permeability of the medium. Discrete discharge of groundwater in the general discharge area results from local inhomogeneities near the land surface. Systematic changes in concentration of anions and cations in groundwater occur in the direction of flow; deviations from expected changes may indicate chemical variability of the porous medium.

Groundwater mapping was done in two areas totalling 230 square kilometers. Four environments of groundwater flow (settings) were outlined from topographic maps. Each setting has a highland and adjacent gently sloping lowlands. A steep walled river valley is present in setting I and part of setting II, and dunes are present in settings II and III. Springs, seepages, hidden seepages, damp soil, vegetation, salt precipitates, soap holes, swamps, less-fertile soils, closed depressions, gullies and contorted meanders were mapped to determine or aid in the determination of relative water conditions on or near the land surface.

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Four chemical types of groundwater were outlined in each area. Waters low in total dissolved solids are associated with regional or local topographic highs, and waters with high total dissolved solids are associated with regional and local lows.

The water table is close to the land surface in relatively low areas, and farther from the land surface in relatively high areas. Groundwater moving away from the land surface is associated with regional and local highlands, and adjacent to steep valley walls. Groundwater moving toward the land surface is associated with lowlands adjacent to the highlands and with local lowlands. The main flow systems in all settings originate on highlands and terminate in part on adjacent lowlands. Local flow systems are important in settings II and III, and are of minor importance in setting I.

Sixteen proposed test hole locations are outlined in the two areas. Locations were chosen with respect to 1) direction of groundwater motion; 2) chemical quality of water; 3) size of recharge area; and 4) probable distribution of rock permeabilities.

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