t8.2 freshwater environments - novascotia.ca

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Topics: Natural History of Nova Scotia, Volume I

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© Nova Scotia Museum of Natural History

T8.2 FRESHWATER ENVIRONMENTS

with the abiotic environment forms the basis of anecosystem.

Lake ecosystems are dominated by autotrophicorganisms (i.e., self-nourishing organisms with theability to produce organic material from simplechemical compounds and sunlight) and are domi-nated by phytoplankton, periphyton and aquaticplants. Lakes can also receive nutrients from outsidesources and may include meteorological, geologicalor biological inputs to the system.1

River ecosystems are dominated by heterotrophicorganisms (i.e., those requiring organic material orfood from other sources) and are characterized byinput of detritus from terrestrial sources. Larger sys-tems which are exposed to sunlight can have au-totrophic components. Primary production from al-gae and rooted plants then becomes an importantenergy source.

Water CoverageApproximately 5 per cent of the land area of NovaScotia is covered by fresh water in the form of lakes,rivers and wetlands, representing a total of 2408 km2.There are 6674 lakes in the province which are greaterthan one hectare in surface area, with a mean surfacearea estimated at 34 hectares.2 Water coverage is not

Surface fresh water can be described according totwo distinct categories: lentic (standing water) andlotic (running water). Lentic environments includesurface waters, such as lakes, ponds and wetlands.Lotic environments comprise rivers or streams.Freshwater environments also occur as continuouslymoving groundwater which has percolated throughthe upper layer of soil to underground storage areas(aquifers). Groundwater can naturally reach aboveground as a spring.

This Topic deals with surface and undergroundaquatic freshwater environments. Wetlands are dis-cussed in T8.3.

SURFACE WATER

Lakes and ponds are formed where an interruptionof the drainage pattern, either by the formation of abasin or by a barrier, restricts the flow of water.Water in surface channels forms the rivers andstreams which ultimately discharge into the ocean.

Ecology of Surface WaterBoth lentic and lotic environments support diversebiotic communities or groups of organisms living ina given area. The interaction of a biotic community

Kejimkujik Park

Chignecto Bay

Minas Channel

Advocate Bay

Unit 710Unit 311

Figure T8.2.1a: Abundant surface water in the granite and quarzite areasof southwestern Nova Scotia (Region 400).

Figure T8.2.1b: Surface water coverage of the permeable rocks of theChignecto Peninsula where lakes are scarce.

Unit 581

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evenly distributed throughout the province, as thesouthwestern section has many more lakes than thenorthern portion. In general, surface water is moreabundant on the granite and quartzites of the Atlan-tic Interior (Region 400) than on the more permeablesedimentary formations in the Carboniferous andTriassic lowlands (Regions 500 and 600) and basaltformations of the Bay of Fundy (Region 700) (seeFigure T8.2.1a and b).

Table T8.1.1 in Freshwater Hydrology indicatesthe amount of water coverage per primary water-shed across the province. In some watersheds thefreshwater coverage has been substantially increasedby the construction of dams.

LAKES

Origin of LakesThe majority of lakes in the province are of glacialorigin and are generally aligned with the direction ofthe ice movement. The lakes of Nova Scotia may becategorized by their origin as follows:• Glacial Lakes—formed either as a basin scoured

out by ice movement or by the interruption ofthe original drainage by the deposition ofglacial till.

• Oxbow Lakes—formed when river meanders arecut off from the main channel, examples can befound in the Stewiacke Valley (District 510).

• Levee Lakes—formed when river sediments

Plate T8.2.1: Mavilette, Digby County (District 820). A small stream flowing through lowlands, showing meander and tidal marsh development. Photo: LRIS

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deposited during periods of high water cause aseparate waterbody to be formed.

• Solution Lakes—formed from dissolvingmaterials such as salt, limestone and gypsum.These lakes can be alkaline and have a highersalt content than most other lakes and occurparticularly in the Windsor (Sub-Unit 511a) andMargaree (Unit 591) areas. Gypsum sinkholesfound in karst topography may contain solutionlakes (see T3.4).

• Barrier or Barachois Lakes—these are createdmainly behind sand or gravel bars in coastalareas and have higher salinity than fresh water.This brackish water condition either is due totidal flow or is the result of salt spray. Primeexamples are found between Gabarus andFourchu Harbour on Cape Breton Island(District 870).

• Beaver Ponds—these are constructed andmaintained by beavers but are regularlyabandoned if and when the local food supply(i.e., poplar, willow, birch and alder) withinreach of the water is exhausted. Some persistfor years; others is only used during the winter(see Plate T11.11.1).

Human-made Lakes• Dammed reservoirs—created principally to

regulate water flow for lumbering, floodcontrol, municipal water supplies or powergeneration and usually contain substantialquantities of coarse to fine woody debris. LakeRossignol, in Sub-Unit 412a, is a good exampleof this occurrence. Waterfowl impoundmentscan increase the area of open water in marshessuch as those found in the Tantramar Marsharea near Amherst (Unit 523).

• Excavated lakes—formed through quarryingand other related activities for example in thegravel quarries at North River near Truro.

Classification of LakesLakes may be classified according to their trophicstatus (i.e., their available phosphate content andbiological productivity):

• Oligotrophic Lakes—those with low phosphateconcentrations and resulting low productivity

• Mesotrophic Lakes—those with moderatephosphate concentrations and resultingmoderate productivity

• Eutrophic Lakes—those with high phosphateconcentrations and resulting high productivity

Highly coloured, low pH lakes resulting from highhumic concentrations are termed dystrophic. Theselakes can have nutrient concentrations and produc-tivity within the trophic states defined above.

Both clearwater and highly coloured(brownwater) lakes exist in Nova Scotia; however,the latter predominate. Most lakes in the provinceare oligotrophic, although some have become eu-trophic due to the impacts from agricultural runoff,domestic sewage and other human activities.Eutrophication is the natural process of lake “aging,”whereby a lake shows a gradual increase in nutrientconcentrations and productivity, slowly infilling withaccumulated organic material. In extreme cases,the decay of the plant biomass can remove oxygen tothe detriment of the other organisms. Hydrogen sul-phide and other gas production can cause unpleas-ant odours. The process can be greatly acceleratedby human activities and is known as culturaleutrophication.

Succession and ZonationIn geological terms, lakes in Nova Scotia are onlytemporary features on the landscape, generallyinfilling to become wetlands, such as peat bogs. Thisis the primary or initial successional stage whichmay lead to the development of an organic matwithin a wetland system.3 Peatlands in Nova Scotiawere formed in this manner. In some systems (e.g.,marshes), the deposition is primarily comprised ofmineral sediments. Refer to T8.3 for continued dis-cussion on wetlands and succession.

Typically, lakes have three distinct zones: the lit-toral or lake edge (hydrosere), the limnetic or surfacewater, and the profundal or deep water (see FigureT8.2.2). In deep-water lakes, the water column can

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also be divided into three zones: the surface water orepilimnion, the bottom water or hypolimnion, andthe area of transition in between called themetalimnion. Thermal stratification can occur wherethe surficial zone becomes much warmer than theprofundal zone during the summer, due to atmos-pheric warming of surface waters and lack of mixing.This creates an area with a steep temperature gradi-ent between the two zones, called the thermocline.When these conditions exist, the surface waters can-not readily mix with the bottom layer and thus thelake bottom may become oxygen deficient. Largerlakes with deeper waters are more likely to stratify.Even though Nova Scotia’s lakes are relatively shal-low, approximately half of them can exhibit thermalstratification. A list of some of the larger lakes in theprovince is provided in Table T8.2.1.

RIVERS

Origin of StreamsStreams originate in headwater areas as outlets ofponds or lakes, or arise from springs and seepageareas. As the water drains away from its source, ittravels in a direction determined by the slope of theland and the underlying rock formations. Waterassociated with a steep gradient carries with it a loadof debris and continues to cut the channel until thematerial is eventually deposited within or along thestream.

Close to its source, a stream may be straight andfast flowing, with many rapids. As the water reachesmore-level land, its velocity is greatly reduced and

��0

2

4

6

8

10

12

14

16

Littoral

(Edge/Hydrosere)

Benthic

Profundal

Bottom

Limnetic(Open Water) Epilimnion

Metalimnion (Summer thermocline)

Hypolimnion

Depth (m)

Figure T8.2.2: Ecological features of a large lake, seen in diagramatic cross section.

the sediment it carries is deposited as silt, sand ormud.4 At this stage, a river is referred to as mature,with meanders which form in large and small loopsas the channel erodes its floodplain (e.g., MeanderRiver in Sub-Unit 511a). Meanders sometimes be-come so exaggerated that they cut off from the mainriver channel to form oxbow lakes (see Figure T8.2.3).

The rejuvenation of a river sometimes occurswhen the it encounters a geological obstacle pro-

Table T8.2.1: Some large lakes in Nova Scotia.


EKAL mk(AERAECAFRUS 2)

)retawtlas(rO'dsarB 0011

*longissoR 861

eilsniA 65

reviRariM 23

kijukmijeK 32

*uaerepsaG 22

dnarG 81

ekunaP 51

*kcowkcoP 8

ekoorbrehS 6

stnemdnuopmiybdegralne*

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ducing a waterfall or fast-flowing rapids. Thus, themature stream then regains some of the charac-teristics of a young stream. Rejuvenated streams arecharacteristic of much of the Atlantic Coast (Region800). Rejuvenation can also occur in response toclimate changes (including sea-level change), tec-tonic events and human activities.

Classification of RiversRiver or stream systems can be extensive and are animportant feature of the landscape. A system gener-ally consists of a number of tributaries that jointogether to form the main drainage channel. Eachstream can be classified according to stream order,which determines the position of the stream in thehierarchy of tributaries. First-order streams have notributaries and when two meet they become second-order streams. Higher-order streams can be fed bytributaries from any number of lower orders.5

FloodplainsIn times of flood, the material carried by streams isdeposited on the land adjacent to the stream banks,which is commonly called the floodplain. Thesefloodplain areas, often referred to as intervales, areutilized by the stream during times of high water andcan help reduce water velocity. As a result, the loss ofriver habitats is minimized. Floodplains also pro-vide important habitat for a variety of plants andanimals known as intervale species (see Sugar Ma-ple, Elm (Floodplain) Forest in H6.1 .

Floodplains generally contain rich alluvial soilsand tend to have been settled extensively. Problemsassociated with development on floodplains initi-

ated a joint federal/provincial mapping program toidentify flood-risk areas in Nova Scotia (see T12.8).The Flood Damage Reduction Program defines aflood-risk area as land which is subject to severeflooding on the average once in 100 years (or there isa 1 per cent chance of being flooded in any given yearto a particular elevation—i.e., the 100-year eleva-tion). A smaller area, known as the designatedfloodway, is the part of the floodplain subject tomore frequent flooding. In this zone, flooding oc-curs on average once every 20 years (or there is a 5 percent chance of being flooded in a given year to the20-year elevation). The designated floodway fringelies between the floodway and the outer limit ofthe flood-risk area. Within this fringe area, anynew building or alteration of an existing buildingrequires appropriate flood-proofing measures if it isto receive federal or provincial assistance.6,7 From abiological perspective, defining flood-plain areas bythe frequency of flooding is very important. Plantand animal species and communities are adapted toflooding regimes.

Comprehensive studies have been conducted fora number of floodplain areas throughout the prov-ince between 1984 and 1989. These include the

The Musquodoboit River is a classic example of a matureriver reverting to a fast-moving stream. The river meandersslowly through the softer sedimentary rocks of the WindsorLowlands (Sub-Unit 511a) and gains momentum again asit cuts through the more resistant Meguma rocks of theGranite Ridge (Unit 453).

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Figure T8.2.3: Physical and ecological features of a meander of a mature river.

A B

Floodplain with alders andsweet gale

Summer water level

Winter/Spring flood level

Spruce,Alder,etc.

Sparganium spp.

Potamogeton spp.Pickerel Weed

SnailsFrogs

Grasses, Sedges, Rushes, Goldenrod

Insects

Note: River flow ratesin spring and winterare about four timesthat of summer

Pool

A

B

Sand & Gravel

Erosion Bank

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Sackville River and the Little Sackville River (Sub-Units 413a and 436a), East River (Pictou in Units521a and 582a), Antigonish-area rivers (Units 521band 583a) and the Truro-area rivers (District 620).

EstuariesAn estuary is that area where the river enters the sea.The runoff of a river into an estuary produces adistinct circulation pattern where the flow of freshwater over the top of the salt water causes nutrient-rich bottom water to be drawn into the estuary andupwelled to the surface. For this reason, estuariesare particularly productive. The strongest influencesoccur at times of heaviest runoff, usually in the spring.A more detailed description of estuaries can be foundin T6.4.

SURFACE-WATER QUALITY

Water quality is influenced by the interaction ofmany natural factors, including bedrock composi-tion, watershed size, response to precipitation, to-pography, vegetation and proximity to the ocean.Cultural influences are also significant (see T12.8).General limnological regions have been delineatedon the basis of geology and soils as shown in FigureT8.2.4.6 The Nova Scotia Department of Environ-ment identifies forty-eight of the fifty-six municipalsurface-water supplies as having significant water-quality problems, some natural and some culturallyinduced.7 These may include colour, taste, odour,bacterial or metal and organic contamination.

Bedrock Composition—ConductivityIn areas of resistant granite and metamorphic bed-rock, where most lakes in the province are found,waters generally exhibit low levels of conductivity,which implies they are low in dissolved solids. Theselakes would have little or no buffering capacity andare very susceptible to acidification. Underwood andSchwartz estimated that 78 per cent of Nova Scotialakes are underlain by granite or metamorphic bed-rock.10 The conductivity of lakes and streams in NovaScotia is generally low and shows little variation be-tween or among most localities. However, somewhathigher levels of conductivity characterize the surfacewaters which drain areas of Carboniferous sandstoneand shales in Cumberland County (Region 500). El-evated conductivity is found in areas where sedi-mentary rocks consist mostly of limestone andgypsum and thus provide a high buffering capac-ity. In a specific study of 781 lakes in Nova Scotia,the mean conductivity ranged from 26.4micromhos/cm (µmho/cm = level of dissolved sol-ids) for lakes in Lunenburg County (Region 400) to655.8 µmhos/cm for those in Cumberland County.2

The mean conductivity for Nova Scotia was 69.5µmho/cm.

Bedrock Composition—ProductivityIn areas underlain by igneous metamorphic rocks,the water contains low electrolyte levels and lakesare generally oligotrophic. This indicates low levelsof dissolved solids, and consequently the amount ofprimary production in the majority of Nova Scotialakes is also considered to be low. Most lakes in theprovince have been classified as relatively unpro-ductive.11,12 Since the level of primary production isdirectly related to fish production, this method hasbeen used to determine the biomass of fish that lakescan support.13

Surface waters draining the Carboniferoussandstones and shales of Cumberland County haverelatively higher levels of conductivity; hence, pro-ductivity is considered to be greater. Comparativelystrong mineralization and high productive capacityare also found in areas where sedimentary rocksprovide a good source of lime, such as in the TriassicLowlands of the Annapolis Valley (District 610) andin the Carboniferous Lowlands of the Stewiacke Rivervalley (Sub-Unit 511a). In these areas, agriculturalactivities are often responsible for additional nutri-ent enrichment.


Nature’s PotteryWhile wading in shallow water of lakes, one may sometimesnotice curious cookie-shaped, concentrically ringed rockslying on the bottom. These unusual stones, known asferromanganese or manganese nodules, are a naturallyoccurring phenomenon in lakes with high levels of manga-nese. The nodules are formed when tiny bacteria,Pseudomonas, become attached to a rock surface and beginto coat themselves with a thick crust of dark-brown manga-nese dioxide. The bacteria then become buried in this sub-stance as successive generations build upon each other overhundreds and even thousands of years. Scientific studies ofthese nodules have revealed some profound effects on themetals in lakes, as the uptake of manganese from the water bythese bacteria is up to 100,000 times greater than the naturalloss due to “rusting” or chemical oxidation of manganese.

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Watershed sizeThe ratio of watershed area to lake size influencesthe nutrient availability to a large extent and deter-mines the flushing rate. Water bodies with undevel-oped watersheds and lower water-renewal rates usu-ally have a low concentration of soluble reactivephosphorous, an important nutrient for plant growth.An increase in phosphorous from human activitieswithin the watershed could lead to eutrophicationand reduce water quality.

PrecipitationPrecipitation influences the rate of runoff, whichcontrols the interaction between water, soils andbedrock, thus influencing chemical composition.Seasonal variations in precipitation, combined withthe saturation of the ground, determines the quan-tity of runoff. During times of high discharge, theamount of dissolved solids entering the watercoursewill be much greater than in times of low water.When certain rock formations are exposed to surface

water, serious water-quality problems can occur. Aprime example of this is the arsenopyrite slate whichis found near Halifax and in other areas underlain byMeguma-bedrock formations. Highly acidic runoffis produced when this type of bedrock is exposed toair and water. The interaction between pyrites, wa-ter and oxygen produces sulfuric acid, which canlead to fish kills. Acid precipitation can also influ-ence surface-water quality (see T12.8).

TopographyTopography contributes to the rate of flow in streamsand rivers and to the width of the floodplain, thusinfluencing the collection of mineral sediments andthe accumulation of peat deposits in the vicinity oflakes. Where the land surface is relatively flat, sedi-mentation rates are quite high. The topography of anarea also determines the shape and size of lakes,whether they are big or small, deep or shallow, roundor irregular. Shallow lakes with irregular shorelinescan provide more favourable conditions for rooted

Figure T8.2.4: Productivity of surface fresh waters in Nova Scotia.8

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plants than large, deep lakes, resulting in more pro-ductive waters.

VegetationConiferous needles can contribute to the organic-acid content of aquatic habitats. They are resistantto decomposition and add few primary nutrients,unlike deciduous litter, which releases nutrientsmore readily and is an important food source foraquatic animals.

SalinityThe salinity of lakes can be attributed both to theocean and to land-based salt sources, including roadsalt. Proximity to the ocean often results in highchloride concentrations from sea spray being car-ried by precipitation to nearby lakes. Since lakes inNova Scotia are no more than 50 km from the ocean,many reflect a marine influence.14 There is a directrelationship between increased freshwater chlorideconcentrations and proximity to the coast.15

Meromictic lakes (i.e., lakes exhibiting incom-plete mixing) may become permanently stratifiedby the intrusion of saline water or salts liberated

from sediments, creating a density difference be-tween surface and bottom layers.2 Examples includePark Lake in Cumberland County (Sub-Unit 521b),where the meromictic conditions are attributed tothe gypsum and salt deposits in the area; LaytonLake in Amherst Point Game Sanctuary (Unit 521a),where conditions are attributed to past inundationsby the sea.16

AciditySurface-water acidity or pH is a measure of themineral nutrients and organic acids present.Distilled water is neutral (i.e., 7.0); however, mostsurface water in Nova Scotia is higher or lower,depending on the relative contributions from hu-mic materials, acidic precipitation and runoff, aswell as the buffering capacity of the bedrock andsoils. In areas containing high concentrations oflimestone, the presence of calcium carbonate inassociation with magnesium strongly influences thebuffering capacity and solubility and hence moder-ates the acidity of the water. Low pH values havebeen shown to affect reproduction of aquatic biotaas well as lowering species diversity.17 The mean pH

Figure T8.2.5: pH values for Nova Scotia.18T8.2FreshwaterEnvironments

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of lakes surveyed in a 1987 study ranged from 5.5 inShelburne County to 7.4 in Inverness County. Theaverage pH in Nova Scotia was 6.2.18 Figure T8.2.5shows the distribution of pH values throughout theprovince.

In Nova Scotia, low pH values (i.e., less than 5.1)are usually associated with bogs and dystrophic wa-ters, as well as areas receiving high levels of acidprecipitation or acidic runoff from freshly exposedpyritic slate formations. The southwestern main-land, parts of the Eastern Shore and the highlands ofCape Breton are considered the most sensitive to theeffects of acid rain.19 Low pH levels have affectedfisheries, especially salmonids, in several southwest-ern Nova Scotia rivers.20,21 A relationship has alsobeen established between sulphate concentrationsin lakes and proximity to the urban centres18 (seeT12.8).

Environment Canada has conducted extensiveresearch into the effects of long-range transporta-tion of air pollutants (LRTP) in the vicinity ofKejimkujik National Park.22 Figure T8.2.6 indicates

the mean annual pH values for the most severelyacidified rivers of the province.

GROUNDWATER

Groundwater is defined as subsurface water thatoccurs beneath the water table in soils and geologicformations that are fully saturated.23 Most ground-water is precipitation that has infiltrated through theupper layers of soil into underground storage areas.It exists nearly everywhere, although quantity, qual-ity and depth can vary according to the type of rockand strata. Groundwater fills the pores or openingsbetween rock particles or the cracks in consolidatedrock. Sediment or sedimentary rock is generally per-meable where the pores are connected and watercan be transmitted. Groundwater moves much moreslowly than surface water but can travel great dis-tances, depending on the topography and the geol-ogy, and ultimately emerge at the surface again. InNova Scotia, however, most flow paths are relativelyshort, mostly due to geological obstructions. The

Figure T8.2.6: Surface-water surveys (1975–85 data) show that the mean annual pH of Atlantic Salmon rivers in the Maritime provinces are above 5.4(considered the danger threshold for salmon), except in Nova Scotia’s Southern Upland, which lies south of the dotted line.

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volume of groundwater is often much greater thansurface water.

Nova Scotia has been divided into threegroundwater regions based on the occurence ofgroundwater in relation to various bedrock orsurficial aquifers24 (see Figure T8.2.7).

AQUIFERS

Soil or rock strata that contain sufficient saturatedmaterial to yield usable quantities of groundwaterfor wells are called aquifers (see Figure T8.1.1 Fresh-water Hydrology). These saturation zones may be oftwo types: unconfined or confined. An unconfinedaquifer is comprised of porous materials such assand and gravel. A confined aquifer is a layer ofwater-bearing material confined within two layersof less pervious material, like clay and shale. The sizeof aquifers can vary greatly according to the type ofstrata. There may also be several small aquifers in anarea, separated by a layer of less-permeable rock .

A large part of Nova Scotia is dominated by bed-rock at or near the surface and most aquifers occur infractures. Some larger aquifers occur in gypsum orsandstone and in overlying surficial deposits. Exten-sive aquifers are found in sand and gravel depositsand in the Triassic Wolfville sandstones of theAnnapolis Valley (District 610)25 and in the Carbonif-erous formations in the Margaree Valley (Unit 591).Large aquifers also occur in other parts of Region 500,in particular in the gypsum areas of Colchester andCumberland counties and in parts of Cape Breton.

Water TableThe water table is the boundary between the upper,unsaturated zone, in which the pores are empty oronly partially filled with water, and the underlying,saturated zone, in which the pores are full of water.In most cases the water table is not flat but generallyfollows the relief of the local topography. In NovaScotia, there is relatively little topographic variation,and the water table is close to the surface.

Figure T8.2.7: Groundwater Regions: Nova Scotia has been divided intothree groundwater regions. These regions are based on the possibility ofconditions, in various bedrock and surficial aquifers, for the occurrence ofgroundwater16. They are briefly described as follows:Groundwater Region 1: Igneous and Metamorphic Rocks.Groundwater Sub-region lA: Plutonic Igneous Rocks.Groundwater Sub-region lB: Metamorphic Rocks.Groundwater is available in these rock types through fractures and joints,and along fault and contact zones. All have similar characteristics in theirabilities to store and transmit water.

Groundwater Region 2: Sedimentary RocksGroundwater Sub-region 2A: Carbonate RocksThe porosity and permeability of carbonate rocks can vary greatly, rangingfrom situations where the rock is only slightly fractured to conditions

where extensive fracturing has occurred. In areas which have carbonaterocks at the surface, enlarged pore spaces in the rocks provide easymovement for contaminants and very little treatment by natural filtration.This results in the aquifers being vulnerable to any sources of pollution.

Groundwater Region 3: DepositsMost of Nova Scotia is covered by glacial deposits which occurred duringthe ice ages and range in thickness up to 30 m in some locations. Some ofthis material was also transported by meltwaters from glacial retreats. Theend result is a wide variety of moraines and eskers, as well as glacial andfluvial outwash found throughout the province. Appreciable depths ofoverburden can affect the occurrence of groundwater.T8.2

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The water table explains the changes in the flowof springs and streams and water-level fluctuationsin lakes. It is also an important factor in determiningthe productivity of wells (see T12.10). In Nova Scotia,wells are typically artesian and occur when the waterlevel in the well rises above the upper boundary ofthe aquifer. An artesian system requires a confinedaquifer with impermeable layers above and belowand hydrostatic pressure created by a higher eleva-tion of the water elsewhere in the aquifer. Someartesian wells can flow constantly and must becapped in order not to waste water from the aquifer.

A perched water table is a special condition wherean unconfined aquifer is situated at some heightabove the main groundwater body and usually oc-curs after periods of heavy rain or spring thaw. Thisphenomenon most commonly occurs along the sideof a valley.26 Wells tapping perched water tables yieldonly temporary or small quantities of water.

GROUNDWATER QUALITY

Groundwater quality depends on the geochemicalcomposition of the strata through which it movesand the length of contact time. Minerals dissolvingfrom the bedrock may contribute to taste, colour,acidity and hardness. Hard water is caused by highlevels of dissolved ions, particularly calcium andmagnesium, which affect the lathering of soap andleave scaly deposits. Soft water is low in dissolvedions and is more prone to acidification.

Groundwater is less vulnerable to airborne pol-lutants than surface water; however, natural depos-its such as uranium and arsenic can cause serioushealth problems. High concentrations of naturallyoccurring iron and manganese in groundwater arewidespread across the province but are not consid-ered to be a health risk. Of the twenty-five majormunicipal groundwater supplies located through-out the province, nineteen have some identifiablewater-quality problems, including colour, taste,odour, bacterial or metal contamination. Arsenicpollution and sulphide mineralization are associ-ated with mines, because the geology that producesgold also tends to produce arsenic from thearsenopyrite in gold veins.27,28,29

Poor-quality groundwater is associated with karsttopography in the Windsor area (Unit 511a). Karstdevelops where carbonate rocks such as limestoneare dissolved, often resulting in sinkholes and un-derground cave networks (see T3.4). Groundwaterin these areas is very high in dissolved minerals.

Soil acts as a natural groundwater filter; however,in many areas of the province the thin till cover

combines with a shallow water table and reduces thefiltration capacity. These areas are susceptible togroundwater contamination from human activitiessuch as landfilling, septic fields and road salting.

Salts and minerals can also be present in ground-water inland. There are several references to brinesprings in a report by A.O. Hayes in 1920.30 Theauthor describes the chemical contents of salt springslocated in St. Patrick’s Channel (District 560, Unit916), Antigonish (Sub-Unit 521b) and Avondale (Unit521a) among others. (The locations of these springshave not been recently verified.) It is suspected thatsome plant species associated with salt springs aresimilar to species found on tidal marshes. Roland 31

reports both Glasswort and Sea-blite growing aroundsalt springs.

The waters of Spa Springs (District 610) werereputed to possess healing properties which attractedmany eighteenth-century visitors to that area. To-day the community is renowned for its bottled min-eral water. The major dissolved mineral in thegroundwater is gypsum which is attributed to thegypsum, lenses found in the late Triassic siltstonesand shales of the Blomidon Formation.7,32–34

Saltwater IntrusionSaltwater intrusion can occur in coastal areas wherewells are constructed close to the ocean. Normally,pressure from the groundwater will restrict sea wa-ter to a zone of diffusion where fresh and salt watermeet; however, during dry periods, water withdrawnby prolonged well use reduces the seaward pressureand allows the salt water to move underground andthus contaminate the well. This may be prevented ifshallower wells are constructed or by reducing theamount of pumping during dry seasons.

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Associated TopicsT2.1-T2.7 Geology, T3.2 Ancient Drainage Patterns,T3.4 Terrestrial Glacial Deposits and Landscape Fea-tures, T5.2 Nova Scotia’s Climate, T6.4 Estuaries,T8.1 Freshwater Hydrology, T9.1 Soil-forming Fac-tors, T10.5 Seed-bearing Plants, T11.5 FreshwaterWetland Birds and Waterfowl, T11.11 Small Mam-mals, T11.13 Freshwater Fishes, T11.15 Amphibiansand Reptiles, T11.16 Land and Fresh Water Inverte-brates, T12.8 Freshwater and Resources, T12.11 Ani-mals and Resources

T8.2Freshwater

Environments

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Associated HabitatsH2.5 Tidal Marsh, H3 Freshwater, H4 FreshwaterWetlands, H6.1 Hardwood Forest

References1 Odum, E.P. (1971) Fundamentals of Ecology.

W.B. Saunders, Philadelphia.2 Alexander, D.R., J.J. Kerekes and B.C. Sabean

(1986) “Description of selected lake characteris-tics and occurrence of fish species in 781 NovaScotia lakes.” Proc. N.S. Inst. Sci. 36 (2).

3 Moore, P.D., and D.J. Bellamy (1974) Peatlands.Springer-Verlag, New York.

4 Smith, R.L. (1990) Ecology and Field Biology.Harper and Row, New York.

5 Hynes, H.B.N. (1970) The Ecology of RunningWaters. University of Toronto Press.

6 Cameron, A. (1992) Flood Damage ReductionProgram. Nova Scotia—Status Report. NationalWorkshop on Flood Reduction—ContinuancePhase. Environment Canada and the CanadianWater Resources Association.

7 Environment Canada and Nova Scotia Depart-ment of the Environment (1981) Nova ScotiaFlood Damage Reduction Program.

8 Smith, M.W. (1963) “The Atlantic Provinces ofCanada.” In Limnology in North America,edited by D.G. Frey.

9 Nova Scotia Department of the Environment(1992) Designing Strategies for Water SupplyWatershed Management in Nova Scotia.

10 Underwood, J.K., and P.Y. Schwartz (1989)“Estimates of the numbers and areas of acidiclakes in Nova Scotia.” Proc. N.S. Inst. Sci. 39.

11 Alexander, D.R. (1975) Sport Fisheries Potentialon Twenty Lakes in the Headwaters of theShubenacadie River System, Nova Scotia.Fisheries and Marine Service. (Tech. ReportSeries No. MAR/T-75-10).

12 Alexander, D.R., and S.P. Merrill (1976) TheUnexploited Brook Trout of Big Indian Lake,Nova Scotia. Fisheries and Marine Service.(Tech. Report Series No. MAR/T-76-4).

13 Ryder, R.A. (1965) “A method for estimating thepotential fish production of north temperatelakes.” Trans. Am. Fish. Soc. 94.

14 Underwood, J.K., J.G. Ogden and D.L. Smith(1986) “Contemporary chemistry of Nova Scotialakes.” Water, Air and Soil Pollution 30.

15 Gorham, E. (1957) “The chemical compositionof lake waters in Halifax County, Nova Scotia.”

Limnology and Oceanography 2 (1).16 Howell, G.D., and J.J. Kerekes (1982) “Ectogenic

meromixis at Layton’s Lake, Nova Scotia,Canada.” J. Freshwater Ecology 1 (5).

17 Kelso, J.R.M., C.K. Minns, J.E. Gray and M.L.Jones (1986) Acidification of Surface Waters inEastern Canada and Its Relationship to AquaticBiota. Fisheries and Aquatic Sciences 87, Depart-ment of Fisheries and Oceans.

18 Underwood, J.K., J.G. Ogden, J.J. Kerekes andH.H. Vaughan (1987) “Acidification of NovaScotia Lakes.” Water, Air and Soil Pollution 32.

19 Clair, T.A., Witteman J.P., and S.H. Whitlow(1982) Acid Precipitation Sensitivity in Canada’sAtlantic Provinces. Environment Canada,Inland Waters Directorate, Water QualityBranch, Moncton. (Tech. Bulletin #124).

20 Watt, W.D., C.D. Scott and J.W. White (1983)“Evidence of acidification of some Nova Scotiarivers and its impact on Atlantic salmon, Salmosalar.” Can. J. Fish. Aquat. Science 40.

21 Watt, W.D. (1986) “The case for liming someNova Scotia salmon rivers.” Water, Air and SoilPollution 31.

22 Kerekes, J.J. (1989) “Acidification of organicwaters in Kejimkujik National Park, NovaScotia.” Water, Air and Soil Pollution 46 1–4.

23 Freeze, R.A., and J.A. Cherry (1979)Groundwater. Prentice-Hall, Englewood Cliffs,N.J.

24 Environment Canada and Nova Scotia Depart-ment of the Environment (1985) HydrologicNetwork Review of Nova Scotia.

25 Hennigar et al. (1992) “Hydrogeological andGroundwater Interests in the Annapolis-Cornwallis Valley.” Geological Association ofCanada. (Atlantic Geoscience Centre FieldExcursion Guidebook C-4).

26 Price, M. (1985) Introducing Groundwater.George, Allen and Unwin, London.

27 Grantham, D.A., and J.F. Jones (1977) “Arseniccontamination of water wells in Nova Scotia.”Water Technology Journal. AWWA, Dec. 1977.

28 Brookes, R.R., J.E. Ferguson, J. Holzbecher, D.E.Ryan and H.F. Zhang (1982) “Pollution byarsenic in a gold-mining district in NovaScotia.” Environmental Pollution 4.

29 Dale, J.M., and B. Freedman (1982) “Arsenicpollution associated with tailings at an aban-doned gold mine in Halifax County, NovaScotia.” Proc. N.S. Inst. Sci. 32.


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30 Hayes, A.O. (1920) The Malagash Salt Deposit,Cumberland County, Nova Scotia. Departmentof Mines, Ottawa. (Memoir 121) (GeologicalSeries No. 103).

31 Roland, A.E., and E.C. Smith (1969) The Flora ofNova Scotia. Nova Scotia Museum, Halifax.

32 Ross, R. (1992) Report on Geothermal Wells(G.T.W.s) GTW 14, GTW 15, GTW 16a and GTW16b. Report to Town of Springhill GeothermalCommittee and Nova Scotia Department ofNatural Resources. Town of Springhill N.S.Geothermal Project.

33 MacFarlane, D.S., and I.R. Fleming (1988) TheUse of Low Grade Geothermal Energy fromAbandoned Coal Mines in the Springhill CoalField, Nova Scotia. Jacques Whitford andAssociates Ltd., Halifax.

34 Coldborne, B.B. (1979) Preliminary Report onWater Supply Systems in Nova Scotia (Popula-tion Greater than 250). Nova Scotia Departmentof the Environment.

Additional Reading• Bond, W.K., K.W. Cox, T. Heberlein, E.W.

Manning, D.R. Witty and D.A. Young (1992)“Wetland Evaluation Guide.” North AmericanWetlands Conservation Council (Canada).(Sustaining Wetlands Issues Paper No. 1992-1).

• Hutchinson, G.E. (1957) “A treatise inlimnology.” In Geography, Physics and Chemis-try, Vol. 1 John Wiley and Sons, New York.

• March, K.L. (1991) A Study of the Productivity ofTwo Headwater Lakes in Nova Scotia. M.Sc.thesis, Acadia University, Wolfville, NovaScotia.

• Strong, K.W. (1987) “Analysis of zooplanktoncommunities of Nova Scotia lakes with refer-ence to water chemistry.” Proc. N.S. Inst. Sci. 37.

• Vannotte, R.L., G.W. Minshall, K.W. Cummins,J.R. Schell and C.E. Cushing (1980). “The rivercontinuum concept.” Can. J. Fish. Aquat. Vol.38.

T8.2Freshwater

Environments

t8.2 freshwater environments - novascotia.ca

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