| Good potential surficial aquifer |
| Glaciofluvial sediments of this region consist mainly of sand and gravel and thus represent a hydrogeological unit with a good aquifer potential. In the centre of the valley, these sediments consist of two main juxtaposed types. On one hand, an extensive outwash plain consisting of well-sorted sandy sediments blankets the valley floor where it partly buries a relatively continuous esker system consisting of sand and gravel ridges. Along the valley edge, particularly along the flank of South Mountain, the glaciofluvial units are more discontinuous and coarser-grained, even bouldery in places, and consist of various ice-contact fans and hummocks. . These sediments overlie mainly the Wolfville formation and their thickness varies between 5-50 m. They have very high hydraulic conductivities and thus, this unit represents an excellent recharge area but that is also quite vulnerable to surface contamination. Groundwater in this unit flows towards tributaries or main rivers (such as Annapolis and Cornwallis). |
| Good or variable bedrock aquifer |
| The good or variable bedrock aquifer hydrogeological unit is composed of three rock formations: Wolfville, Blomidon and North Mountain. The Blomidon Formation overlies the Wolfville Formation. These two formations comprise lenticular bodies of sandstone, conglomerate, shale and siltstone in different proportions that form a discontinuous and layered aquifer/aquitard sequence.The Woflville Formation is dominated by coarser grained facies, whereas the Blomidon Formation is characterized by more fine-grained strata. The North Mountain Formation overlies the Blomidon Formation and is composed of basalt. The rock formations are covered by different deposits: mainly till, but also glaciofluvial and glaciolacustrine sediments. The Wolfville and Blomidon formations represent the two main aquifers of the Valley. Water-bearing fractures in these two formations seem to be mostly associated with bedding planes gently dipping towards the Bay of Fundy. Conversely, the North Mountain basalts contain mainly vertical fractures that can provide good yields on a local basis only because low fracture interconnectivity limits the flow circulation. Groundwater flows towards the center of the valley, generally following the topography. The Wolfville aquifer is the most vulnerable bedrock formation in the area. The groundwater quality is generally good, but nitrate concentrations are of concern in several areas. In addition, some aesthetical criteria, such as those for iron and manganese, are often exceeded and some wells show a pH below the minimum recommended limit (<6.5). |
| Low potential aquifer |
| The low potential aquifer hydrogeological unit is composed of three main geological units: the South Mountain batholith, as well as the Meguma and Horton Groups. The South Mountain batholith includes metasedimentary and granitic rocks; it forms the highland region of central Nova Scotia. The Meguma Group's youngest unit, the Halifax Formation (Lower Ordovician), covers a large region in the southeastern part of the study area; it is composed of interbedded slate, siltstone, and quartzite. In the extreme eastern end of the Valley, the Meguma Group is overlain by the Horton Group, which consists in its upper part of shale with interbedded grits and sandstones. Strata are lenticular and crossbedded, typical of Maritimes Basin units. The rock formations are covered by a till layer. Hydraulic conductivity values range between 10^-7 and 10^-6 m/s, but very few data are available, as this area is sparsely populated. Groundwater flows from the topographic highs of the South Mountain to the centre of the Valley floor. The aquifers vulnerability is low. Groundwater quality is generally good, but very few data are again available, except in the eastern part of the valley. Iron and manganese are often in excess compared to aesthetical criteria and some wells show a pH below the minimum recommended limit (<6.5). |
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