APPENDIX C: WATER-TABLE ELEVATIONS IN EASTERN BARNSTABLE, MASSACHUSETTS 

 Cape Cod Aquifer Management Project Final Report Page C-4 



important features. The first is a large "mound" of ground water east of 

 Wequaquet Lake. During the May, 1987 observation period, its elevation was 

 over four feet higher than this large surface water body. The mound's 

 elevation and shape indicate that water flows radially outward near the 

 intersection of Pitchers Way and Bearses Way. In the area between the 

 center of the mound and Wequaquet Lake, the direction of ground-water 

 flow is to the west, while regional flow directions in this part of Cape 

 Cod are generally eastward. Another noteworthy feature shown by the water 

 table map is the effect of Wequaquet Lake on local ground water flow direc- 

 tions. With an area of over one square mile, Wequaquet Lake is the larg- 

 est surface water body on Cape Cod. The water lost by evaporation and the 

 herring run outlet on its southern shore is replaced by ground water dis- 

 charging to the pond along its western, northern and eastern shores. In 

 addition, lake water recharges the aquifer along its southern shore and 

 moves in the direction of Nantucket Sound. 



The relationship between Wequaquet Lake and the mound of ground water has 

 important implications for water management strategies and the delineation 

 of wellhead protection areas in this portion of Barnstable. As the eleva- 

 tion of the water table fluctuates in response to aquifer storage, the 

 gradient (or slope) of the water table between the lake and the mound's 

 center may also change. As the amount of ground water in storage in the 

 aquifer decreases, the elevation of the water table and of the mound will 

 decrease as well. The water-table gradient towards the lake will be less 

 pronounced and less discharge into the lake from the area of the mound 

 will occur. Because season and climate affect the direction and velocity 

 of ground-water flow, they must be considered when delineating recharge 

 zones near pumping wells and when determining contaminant flow direction 

 and velocity. 



All but one of the 71 wells used as observation points are screened in the 

 shallow sand and gravel aquifer underlying the mapped area. They range in 

 depth from 6 to 102 feet. Beneath this permeable layer of varying thick- 

 ness are extensive clay strata which locally are quite thick. For example, 

 Well AlW 318 (No. 68) in northern Barnstable is screened in 77 feet of 

 clay to a depth of 87 feet. Because the clay confines the aquifer in this 

 area, ground water is artesian and tends to flow from wells onto the land 

 surface. In the Hyannis area, well C-4 (No. 22) penetrated 15 feet of 

 "blue clay" and gray sandy silt from 50 to 65 feet below the land surface 

 (Maravell and others, 1983). 



Precision and Accuracy 



Every attempt was made to reduce potential sources of error. Mistakes may 

 occur in measuring or recording the depth to water at a well due to water 

 condensation or pressure variations within the well casing. If a depth 

 measurement was uncertain at the first attempt, the field observer made 

 additional measurements until the true depth to water was confirmed. In 

 all cases, the precision of measurement sought was .01 feet. Errors may 



