Good potential surficial aquifer

Aquifer

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Good potential surficial aquifer unit description

Update:2014-02-07
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).
Physiography
Hydrogeological regionAppalachians
Hydrogeological context
ReliefThe elevation of these glaciofluvial formations, located in a large part in the center of the valley, is commonly low. Elevations generally do not exceed 50 m. However, on the South Mountain flank, their elevation can reach 100 m. These sediments are mainly present in a sector that is relatively flat, except for the mountain flank where slopes can reach 5 to 10%.
Area244.00 km2
Lithology
DescriptionThe good surficial aquifer hydrogeological unit consists of glaciofluvial deposits such as subaerial proglacial fan and ice contact sediments. In general, the sediments are sandier and better sorted in the centre of the valley, whereas gravel and boulders are found along the flank of South Mountain. An extensive outwash plain occupies much of the central part of the valley. Outwash sediments usually consist of well stratified and cross-bedded fine to coarse sand. These surficial sediments overlie Wolfville formation.
Source
Aquifer
AquifersList of the aquifers - Granular surficial aquifer

Unit properties

Surficial aquifer media
Typical value:porous
Description This unit comprises glaciofluvial deposits such as proglacial fan sediments and ice contact sediments, including numerous esker segments.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Confinement
Typical value:unconfined
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Surficial sediment thickness
10 m Range: [0 to 50] m
Description The thickness of these deposits typically varies between 5 and 15 m, but a few areas show thicknesses between 15 and 50 m.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Methode Values mainly come from well drilling logs in the provincial databases.
Hydrogeological unit thickness
10 m Range: [ to 45] m
Description The thickness of unconfined aquifers corresponds to their saturated thickness. Since the water table is located, on average, at a 5.5 m depth in this unit, these aquifers would thus often have a thickness of less than 6 m, but they could probably reach 30 to 40 m in a few places.
Source CANADIAN GROUNDWATER INVENTORY: REGIONAL HYDROGEOLOGICAL CHARACTERIZATION OF THE ANNAPOLIS VALLEY AQUIFERS
Methode Values mainly come from well drilling logs in the provincial databases.
Well depth
27 m Range: [0 to 45.7] m
Description The mean well depth varies with the well type (multi-users vs residential).
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Methode Values mainly come from two provincial databases: the pump test database (multi-user wells) and the well log database (residential wells).
Groundwater depth
5.6 m Range: [0 to 10.1] m
Description The mean groundwater depth varies as a function of the well type (multi-users vs residential).
Source CANADIAN GROUNDWATER INVENTORY: REGIONAL HYDROGEOLOGICAL CHARACTERIZATION OF THE ANNAPOLIS VALLEY AQUIFERS
Methode Values mainly come from two provincial databases: the pump test database (multi-user wells) and the well log database (residential wells).
Surficial unit hydraulic conductivity
0.0013 m/s Range: [4.8e-06 to 0.016] m/s
Description Available hydraulic conductivities for these sandy units are very high, typically in the order of 10^-5 to 10^-3 m/s. These are by far the most permeable units in the study area.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Methode Values are mainly based on available data from the pump test provincial database.
Regional precipitation
1238 mm/y Range: [952 to 1468] mm/y
Description The area covered by the study receives a constant supply of precipitation annually, although the winter months are characterized by higher rainfall. Between 15% and 25% of precipitation is in snow form. Overall, the valley is slightly drier and warmer than the highlands. It is established that the valley annually receives 1 138 mm of water.
Methode The data are taken from 15 meteorological stations in the region or around the study area. Observations took place in a period of 5-73 years.
Regional evapotranspiration
468 mm/y Range: [441 to 496] mm/y
Description As glaciofluvial formations cover mainly the Wolville Formation, the same values as for this bedrock formation are being used.
Source Regional recharge estimation using multiple methods: an application in the Annapolis Valley, Nova Scotia (Canada)
Methode Values have been obtained using two methods (soil moisture balance and the hydrological model HELP).
Regional runoff
342 mm/y Range: [250 to 434] mm/y
Description As glaciofluvial formations cover mainly the Wolville Formation, the same values as for this bedrock formation are being used.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Methode Values have been obtained using three methods (stream hydrograph separation, soil moisture balance and the hydrological model HELP). Only the last two methods provide values per formation.
Regional recharge
350 mm/y Range: [300 to 400] mm/y
Description These granular aquifers have very high recharge rates , likely in the order of 300 to 400 mm/y, close to values estimated using hydrograph separation.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Methode Since the regional aquifer in this region is within bedrock, values have mainly been estimated for this aquifer. A value of 350 mm/y was assigned to coarse sediments in the FEFLOW model.
Regional discharge
Description Discharge zones correspond to streams (e.g. Annapolis and Cornwallis rivers).
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Hydrogeological unit potential
Typical value:high regional
Description Sand and gravel deposits have a very good aquifer potential, in fact the best in the region, but they are vulnerable. In addition, they are limited in extent because their saturated thickness must be at least of a few meters to supply enough water. This occurs mainly in the eastern part of the Valley.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Aquifer vulnerability
7 Range: [3 to 8]
Typical value:very high - high
Description The susceptibility to contamination of the surface by these fluvioglacial sediments generally ranges from high to very high since they are directly on the surface, their K is high and the water table is relatively close to the surface.
Source Canadian groundwater inventory: Hydrogeological atlas of the Annapolis Valley, Nova Scotia
Methode These results are based on categories established following the use of the well-known DRASTIC method.
Groundwater Quality
Description Groundwater quality is generally good, but nitrate concentrations are of concern in several areas.
Methode Data came mainly from provincial databases, but also from a federal database (EC), from Kings County, from a local organisation (CARP) and from our own fieldwork. Few samples were available for surface wells.