Good potential surficial aquifer

Aquifer

Version	Metadata
	c6bcd44b-8ceb-4267-a2f7-09dcff7b4f38

Project
Annapolis-Cornwallis Valley

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Good potential surficial aquifer unit description

Update:2014-02-07

Physiography
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).
Hydrogeological region	Appalachians
Hydrogeological context
Relief	The 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%.
Area	244.00 km2
Lithology
Description	The 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
Aquifers	List 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.