Humber River State of the Watershed Report - Geology and Groundwater Resources … ·...

Humber River State of the Watershed Repor t –

Geology and Groundwater Resources

32

4.0 HYDROGEOLOGY

This section builds on the geologic framework presented in Section 3 and describes the

prevalent groundwater flow regime through different geologic units. The discussion in this section starts with a description of the hydrostratigraphic framework and then describes the

mechanism of water infiltration into the ground surface, movement of groundwater in the

subsurface and finally where groundwater leaves the subsurface or intersects with the ground

surface (groundwater discharge). This section also briefly summarizes available groundwater

quality data, information regarding aquifer vulnerability and provides an overview of on-going

work to develop and refine the numerical groundwater flow model.

4.1 HYDROSTRATIGRAPHY

Hydrostratigraphy differs from the geologic stratigraphy in the sense that hydrostratigraphic

layers represent a classification of the geologic units into aquifers or aquitards, and also

combines different geologic units with similar hydraulic properties into single hydrostratigraphic

units. As is the case with all the geologic units, all hydrostratigraphic units may not occur

everywhere throughout the watershed. The term “aquifer complex” designates a unit where the

majority of the sediments have moderate to high permeability although the sediments may vary

both vertically and laterally.

Aquitards and tills are usually much more extensive and uniform than coarse grained

permeable material and therefore, it is easier to identify and map an aquitard layer as

compared to aquifer material. The hydrostratigraphic layers termed as “aquifer” are not always

of high permeability since the depositional mode is quite complex and fine grained sediments,

like silt, are usually present.

The hydrostratigraphic units influencing groundwater flow within the watershed are as follows:

� Layer 1: Surficial Aquifer (includes weathered Halton Till) � Layer 2: Halton Aquitard

� Layer 3: Oak Ridges Aquifer/ Mackinaw Interstadial (ORAC, includes ORAC Silts)

� Layer 4: Newmarket Till

� Layer 5: Thorncliffe Aquifer (TAC, includes Tunnel Channels)

� Layer 6: Sunnybrook Aquitard

� Layer 7: Scarborough Aquifer (SAC, includes all older sediments)

� Layer 8: Weathered Bedrock

Characteristics of the hydrostratigraphic units that influence the flow of groundwater in the

watershed include:

� Configuration of the bedrock valleys and their degree of connection with other aquifers;

� Thickness and lateral extent of the Newmarket Aquitard which separates the shallow

and deeper groundwater systems. Similarly, the Sunnybrook Aquitard strongly

influences the deeper groundwater flow system as it separates the two lower aquifers

(TAC and SAC);

� The location of tunnel channels in the watershed area; and, � Thickness, lateral extent and nature of the sediments in the aquifer complexes.



33

In addition to the three major aquifer complexes (ORAC, TAC and SAC) some researchers

consider the tunnel channel infill deposits as a separate aquifer complex otherwise known as

Channel Aquifer Complex. Tunnel channels have possibly eroded into or through the

Newmarket Aquitard. In most instances, the Channel Aquifer Complex is hydraulically connected with the Thorncliffe Aquifer Complex but can represent a different hydraulic unit

from the Thorncliffe Aquifer Complex. The upper portion of the tunnel channel infill deposits

may contain finer material and function like an aquitard, providing some degree of hydraulic

isolation from the Oak Ridges Moraine deposits. Occasionally, the finer material is termed as a

Channel Aquitard. In addition, within the ORAC the finer sediments have been classified as

ORAC silts. These deposits exist mostly in the main Humber River watershed.

Figure 4-1 shows the locations of three cross-sections of the hydrogeologic model (Kassenaar

and Wexler, 2006) in plan view. The cross-sections are provided on Figure 4-2 , Figure 4-3, and Figure 4-4. These sections illustrate the hydrostratigraphic layers present in the Main

Humber River, East Humber River, and West Humber River, respectively.

Figure 4-2 highlights the sub unit ORAC Silts within the main ORAC between King Road and

Highway 50 (Earthfx, 2007a) and the relatively thin overburden present along the main Humber

River, with the exception of the Laurentian Valley that is prominent at King Road. This is a

distinct contrast to the East Humber section (Figure 4-3), that highlights thick aquifer

sequences around Kipling Avenue and between Bathurst Street and Bayview Avenue. The West Humber section (Figure 4-4) shows the thick ORAC at King Street, and the general lack

of any significant aquifer systems to the south (although the Scarborough aquifer is locally

thicker around Highway 7 and again at Finch Avenue). Most of the groundwater/surface water

interactions are expected to occur in the areas where the aquifers pinch out, and the overlying

aquitard thickness is less than 5 m.

Figure 4-1:

Geologic Model Cross Section Locations

Figure 4-2:

Main Humber River Profile

Figure 4-3:

East Humber River Profile

Figure 4-4:

West Humber River Profile



38

4.2 WATER BUDGET

The hydrologic cycle or water cycle, as shown on Figure 4-5 is familiar and understood by

watershed stakeholders. A water budget describes in a quantitative way the major

components of the hydrologic cycle within a watershed, which provides a measure of the

balance that exists in the system. The most widely recognized components of the hydrologic cycle are precipitation, evaporation, and stream flow. In preparing a water budget, the

hydrologic cycle can be further subdivided into components that account for plant

transpiration, surface run-off, groundwater recharge and groundwater flow.

Figure 4-5: Hydrologic Cycle

Precipitation and stream flow can be directly measured using field instrumentation, with

recorded data for these parameters going back many decades in the GTA. The difference between total precipitation and stream flow volumes for any given watershed varies

considerably.

The difference between these components represents the net loss to the system due to the

combined effect of evaporation and plant transpiration (referred to as evapotranspiration). The

difference between total precipitation and evapotranspiration is generally referred to as water

surplus. The water surplus may be partitioned between the water that infiltrates into the ground

(groundwater recharge), and that which enters local streams as surface run-off. Since the

groundwater recharge usually re-enters the watercourses as groundwater discharge, baseflow separation techniques assist in achieving this partitioning (Weissman, 1989). The process is

cyclical, with the evapotranspiration losses entering the atmosphere, to subsequently form

precipitation in another watershed.



39

Groundwater management becomes necessary when human use and urban development

interferes with the natural hydrological cycle. Groundwater management must be based on a

water budget for the watershed which balances the inflow to and the outflow from the

groundwater system. It must also provide the parameters necessary to make optimal use of the

water in storage. The factors on which the balance is based represent average values derived

from directly measured data and from assessments based on estimates. As more measured data become available, parameter uncertainty decreases, with a resulting improvement in

estimates.

The quantitative equation of the water budget is as follows:

∆ S = P- R – ET- Inf

Where: ∆ S = Change in water storage P = Precipitation

R = Run-off (surface water)

ET = Evaporation and transpiration (Evapotranspiration)

Inf = Infiltration

Application of water budget analyses enables assessments to be made regarding the effect of

urban development on the hydrologic cycle and also allow estimates to be made of

groundwater recharge rates on a spatial basis for both existing and future land use conditions.

This approach also facilitates the identification and evaluation of alternative mitigation techniques needed to maintain existing groundwater levels following urbanization of an area.

TRCA has completed water budget assessments for the 905-area code portion of the Humber

River watershed using HSP-F (HCCL, 2006) and for the Upper Humber River watershed using

WABAS methodology (Clarifica, 2003a). The City of Toronto has completed a water budget

assessment for their portion of the Humber River watershed using HSP-F (XCG Consultants

Ltd., 2003a). Inputs to the models include:

� Daily precipitation; � Average or maximum daily temperature;

� Pan evaporation;

� Daily stream flow measurements;

� Physical basin parameters including imperviousness, interception abstractions; and

� Vegetation and soil characteristics

The outputs from the model include a time series of:

� Run-off; � Infiltration;

� Evaporation; and

� Storage conditions within the water reservoir (pervious and impervious interception

storage, surficial soil storage and snowpack storage).

The groundwater model developed by the YPDT-CAMC Groundwater Management Study team

can be used to simulate groundwater flow conditions. This model predicts average annual

groundwater levels, flow directions, and discharge areas and rates. To facilitate assessment of current and future land uses, TRCA initiated water budget modelling work that builds on the



40

previous surface and groundwater modeling work. The new models use the Precipitation Run-

off Management System (PRMS) program developed by the USGS to calculate infiltration rates

that can then be input into the MODFLOW groundwater model. Although the two models are

not directly linked, they can be run iteratively to confirm that their outputs are consistent.

4.2.1 Precipitation

As mentioned in Section 1.0, precipitation varies across the watershed both spatially and

temporally with local variation created by such factors as topography, prevailing winds and

proximity to the Great Lakes. Average annual precipitation measured at 48 stations within the

regional groundwater model (Core Model) area, which includes the TRCA watersheds, York

Region, and parts of Peel and Durham Regions, ranged from 734 to 946 millimetres for the

period of 1980 to 2002. The average annual total precipitation for the seven active Environment

Canada climate stations, within or near the Humber River watershed, ranges from 798 to 933 millimetres (Environment Canada, 2007).

4.2.2 Evapotranspiration

This value is not directly measurable but can be calculated using empirical formulae based on

calibration in many watersheds (Thornthwaite and Mather, 1957). The mean annual potential

evapotranspiration for the period 1971 to 2000 ranges from 575 mm along the moraine to 600

mm along the shore of Lake Ontario in Toronto. This compares to estimates of 559 to 584 mm by Phillips and McCulloch (1972) for the Great Lakes Region. Estimates of actual

evapotranspiration by Phillips and McCulloch (1972) range from 533 mm/yr to 559 mm/yr. The

mean annual actual evapotranspiration for the region including the watershed is assumed to be

533 mm.

4.2.3 Run-off

Any precipitation that doesn’t transpire or evaporate will infiltrate or form local run-off. As mentioned earlier, the water surplus ranges from 277 mm to 383 mm. In a simplistic and

practical sense, the stream flow hydrograph based on daily average flows can be separated

into two components - run-off and groundwater discharge. Interflow (unsaturated zone flow) is

not explicitly estimated in this treatment but assumed to be included in either recharge or run-

off.

A HYMO based hydrologic model has been developed by the TRCA for the Humber River

watershed to simulate run-off from single design storm events (i.e., 2-100 year and Regulatory

Storm). Results from the model have served as input to develop a river hydraulic model (HEC-RAS) in order to calculate floodlines, which in turn have been used to produce floodplain maps.

A second surface water modelling initiative uses a continuous simulation hydrologic model,

Hydrologic Simulation Program – Fortran (HSP-F) to estimate water budget components and

predict surface water flow and quality. Simulations have been run using climate data inputs

from 1990 to 1996 in the Toronto, York Region and Peel Region portions of the Humber

Watershed (XCG Consultants Ltd., 2003a; HCCL, 2008).



41

4.2.4 Recharge

Recharge or infiltration to the groundwater system occurs by the migration of precipitation

through the surficial soil. The amount of recharge or infiltration at a specific site depends on

the amount of precipitation evaporated back into the atmosphere, the amount of water

transpired from natural vegetation to the air, site topography, type of vegetation and surficial soil type. Surficial geology influences recharge rates. Areas of hummocky topography exhibit

higher recharge rates since soil run-off collects in depressions where it can then infiltrate

through the surficial soils, while clay till has limited recharge potential. Reduction in recharge

within urban settings occur due to hard surfaces (e.g. driveways, roads or roofs).

Figure 4-6 shows the net recharge areas and estimated rates within the watershed based on

the Humber Watershed PRMS Water Budget Model (Earthfx, 2008). The major recharge areas

within the Humber Watershed occur in the north, on the Oak Ridges Moraine, where infiltration to surficial sand and gravel deposits exceed 200 mm/yr. Increased infiltration occurs in

hummocky terrain, which occurs over most of the Oak Ridges Moraine area. This terrain

results in internally drained areas and areas with indeterminate drainage, which results in a

general absence of stream channels.

Till or till with a lacustrine veneer covers much of the southern flank of the ORM. Unit recharge

rates for these deposits are much less than for the granular materials within the ORM.

Recharge rates over the till deposits is estimated to be in the range of 50 to100 mm/yr.

The southern portion of the watershed contains glacial Lake Iroquois shoreline deposits that

exhibit different unit recharge rates depending on the type of deposit. The Lake Iroquois beach

sand and gravel deposits exhibit high unit recharge rates except for where upward vertical

gradients occur along the break in topographic slope.

Figure 4-6:

Estimated Groundwater Recharge Rates; mm/year (Earthfx, 2008)



43

4.2.5 Storage

Storage represents the volume of groundwater contained in the pore spaces of unconsolidated

material or fractures within bedrock aquifers. Although water levels vary seasonally, over the long term, the change in storage is zero. This approach assumes that groundwater is used at

sustainable levels.

If a flow system such as the Humber River watershed, is considered as a closed system and

long term storage changes are assumed to be equal to zero, then the total precipitation minus

total stream flow minus underflow to other aquifer systems can be considered an

approximation of the amount of evapotranspiration that is occurring from the watershed.

Similarly, in a closed system without long-term changes in storage the amount of groundwater

recharge can be assumed to approximate the amount of groundwater discharge to streams and groundwater abstraction. An assessment of stream flow is then an important component

of any hydrogeologic investigation, particularly the water budget component. The summary of

stream flow data contained in the Humber River State of the Watershed Report – Surface Water

Quantity (TRCA, 2008) provides an estimate of the groundwater discharge component of the

total stream flow.

4.2.6 Groundwater Flow

Groundwater flow direction within all aquifers in the watershed is generally from the ORM in the

north to Lake Ontario in the south. Local flow occurs eastward off of the Niagara Escarpment

with local deflections occurring near streams and associated valleys. For all aquifers, the flow

patterns generally follow the surficial aquifer divides, with the exception of the northwest and

northeast corners. Further discussion by aquifer unit is provided below.

The headwaters area of the watershed generally functions as a groundwater divide for all three

aquifer systems in the Humber Watershed. However, this divide is less pronounced in the

vicinity of Nobleton, perhaps due to the influence of tunnel channels within the subsurface that may be allowing some inter-basin flow of groundwater from the Lake Simcoe Watershed into

the Humber Watershed. Some inter-basin flow is also believed to occur from the Credit River

watershed into the Humber River watershed and from the Humber River watershed (East

Humber subwatershed) to the Rouge and Don River watersheds. The divide also becomes

complex where the Oak Ridges Moraine meets the Niagara Escarpment in the Mono Mills Area.

The water table elevation map derived from observed water levels in Ontario Ministry of the

Environment (MOE) water well records (Figure 4-7) shows the expected strong influence of the surficial features (Escarpment, ORM, watercourses) on the water table. Note the predicted flow

into the Humber watershed from the Credit River watershed, and predicted outflows to the

Rouge and Don River watersheds around Oak Ridges. Figure 4-8 highlights where the water

table is shallow (within 2 m of ground surface). Note in the depth to water table map that the

shallow water table areas correspond to the uppermost reaches where the streams arise, and

that the Main Humber has more shallow water table areas (particularly in the Nobleton area)

than either the Upper East or West. Also, in the lower reaches where the river is deeply incised,

there are extensive areas of shallow water table.

Figure 4-7:

Water Table Elevation (in metres above sea level)

Figure 4-8:

Depth to Water Table (in metres)



46

In the Oak Ridges Aquifer (Figure 4-9), the flow patterns are still directly influenced by

topography and the stream network. As with the shallow groundwater, inflows from the Credit

River watershed are predicted around Caledon East and significant outflows to the Rouge and

Don River watersheds are predicted in the Oak Ridges area.

In the Thorncliffe Aquifer (Figure 4-10) the effect of topography is more subdued than the

upper aquifer system (ORAC), but the inflows and outflows are still predicted to occur in the

Caledon and Oak Ridges areas, respectively.

In the Scarborough aquifer (Figure 4-11), the effects of the Escarpment and Oak Ridges

Moraine are still prominent, but there is no significant effect from the watercourses until the

middle reaches of the Main Humber, south of Kleinburg. The inflow from the Credit River

watershed is greater than in the upper aquifer systems, as evidenced by the closely spaced contours off the edge of the escarpment.

Figure 4-9:

Modeled Oak Ridges Aquifer Water Levels (in metres above sea level)

Figure 4-10: Modeled Thorncliffe Aquifer Water Levels (in metres above sea level)

Figure 4-11: Modeled Scarborough Aquifer Complex Water Levels (in metres above sea level)



50

4.2.7 Groundwater Discharge

Groundwater leaving a watershed constitutes the discharge component of the water budget.

Groundwater discharge to streams, water takings via water wells, and underflow to another watershed constitute the “discharge” component of a water budget. The Permit to Take Water

Groundwater (PTTW) program of the Ministry of Environment provides initial data on

groundwater use within a watershed. Stream flow data assists in determining estimates of

groundwater discharge by hydrograph separation techniques (see TRCA, 2008).

As can be seen on Figure 4-12, the major zone of groundwater discharge to streams within the

Humber River watershed occurs along the southern flank of the Oak Ridges Moraine.

Centreville Creek, and the upper Main Humber comprise the main groundwater discharge

zones. Another major zone of groundwater discharge to streams occurs south of the Lake Iroquois shoreline where there are strong upward gradients from the Thorncliffe and

Scarborough Aquifers, and the confining units are thin or absent.

Figure 4-13 illustrates the spatial distribution of groundwater discharge determined from the

low flow stream flow surveys performed in 2004 (TRCA, 2008). The figure illustrates the portion

of total baseflow from the Humber that each secondary subwatershed unit contributes. This

information confirms that significant discharge zones are associated with areas along the flanks

of the Oak Ridges Moraine, particularly in the northwest and northeast portions of the watershed, and where aquifer units are believed to outcrop along the stream corridor.

Uncertainty remains as to whether the observed baseflows along the highly urbanized reaches

in Vaughan and Toronto are a result of groundwater discharge or a combination of

groundwater discharge, storm sewer discharges and/or leakage of urban infrastructure (Hinton

et al., 1998).

Baseflow discharge from the East Humber River is almost double that of the West Humber

River, which has a drainage area of similar size. This difference is likely because the headwater tributaries of the East Humber River originate on the ORM (i.e., area of high recharge rates)

whereas the majority of the West Humber River tributaries originate on the till plain (i.e., area of

low recharge rates).

Figure 4-12: Modeled Groundwater Discharge to Streams



52

Figure 4-13: Contribution to Total Baseflow by Humber River Secondary Subwatersheds

4.2.8 Groundwater Use

Generally, urban areas of the watershed depend on surface water from Lake Ontario for their

water supply needs while the rural areas, including small urban centres such as King City, Nobleton, Caledon East, Palgrave and Kleinburg, rely on water from individual and municipal

wells. Historically, the increased reliance on water supplies from Lake Ontario has followed

urban expansion northward. There still remains a rural population reliant on private single-

dwelling water supplies obtained from groundwater. Groundwater is also used for commercial,

industrial, agricultural and recreational (i.e. golf course) purposes.

Groundwater takings occur from the major water-bearing hydrostratigraphic layers identified

within the watershed. This includes potable water supply, agricultural irrigation, industrial

processing, commercial and recreational purposes (such as golf course turf irrigation). Groundwater provides the source of potable drinking water for the rural residents of York

Region and Peel Region in addition to the Town of Mono (Dufferin County). Presently, twelve

(12) municipal water supply wells within the Humber River watershed provide drinking water to

approximately 21,000 individuals.



53

The Ministry of Environment regulates water takings (including from groundwater sources) at

rates greater than 50,000 litres per day and managed through its PTTW program. Actual water

consumption is generally less than the maximum permitted water taking.

York Region currently operates six wells within the Humber River watershed while Peel Region

operates another six. Groundwater use for municipal water supply purposes is declining due to

the limited resource available to meet growth requirements. Figure 4-14 shows the location of

these municipal wells. Table 4-1 provides a list of municipal wells, the hydrostratigraphic layer

into which they were completed, the average pumping rate (1990- 2002) and the peak (or

maximum) pumping rate as identified in their corresponding Permit to Take Water (Gartner Lee,

2006).

Total municipal groundwater use in the watershed is about 9,500 m3/day based on the average

pumping rate of 12 wells and a maximum permitted rate for the remaining well (Palgrave #4,

2,600 m3/day). Individual well production records suggest that withdrawals are much less than

the permitted maximum rates.

Table 4-1: Municipal Water Supply Wells, Humber River Watershed

Well Name Aquifer Layer

Average

Pumping Rate

(m3/day)

Maximum

Permitted Rate

(m3/day)

Remarks

YORK REGION

King City # 3 TAC 9503 1964

King City # 4 TAC 9613 2620

Kleinburg # 2 TAC 993 238

Kleinburg # 3 SAC 7613 3285

Nobleton # 2 SAC 2124 19644

Nobleton # 3 SAC 8524 19644

PEEL REGION

Palgrave # 2 TAC 4011

Palgrave # 3 TAC 13341

Palgrave # 4 SAC 26182 2620

2 Pump design rate

(Peel data, January

2008)

Caledon East # 2 ORAC 891

Caledon East # 3 ORAC/ Tunnel

Channel 1001

Caledon East # 4 TAC 10871

45005

5 Combined average

permitted rate of

Caledon wells is 1800

m3/day

Note: 1 Data provided by Region of Peel, January 2008, based on actual use in 2006. 2 Data provided by Region of Peel, January 2008 based on pump design rate. 3 Data from Beatty and Associates (2003). 4 Data from MMM Ltd. Nobleton EA (2007). 5 Data from Stantec, Caledon East EA (2007)

TAC - Thorncliffe Aquifer Complex

SAC- Scarborough Aquifer Complex

ORAC- Oak Ridges Aquifer Complex

Figure 4-14: Locations of Municipal and PGMN Wells



55

King City - King City currently operates two wells producing about 2,000 m3 per day. These two

wells extract groundwater from the Thorncliffe Aquifer Complex. Further Investigations continue

for the development of a third well to accommodate increased residential demand associated

with projected population growth.

Kleinburg - The Region of York operates two wells in Kleinburg, producing approximately 1,000

m3 per day principally extracted from the Scarborough Aquifer Complex.

Nobleton - The Region of York operates two wells in Nobleton providing approximately 1000 m3

per day of groundwater extracted from the Scarborough Aquifer Complex. Investigations

continue for the development of a third well to accommodate increased residential demand

associated with projected population growth.

Palgrave - The Region of Peel currently operates three permitted wells in the Palgrave well field,

Palgrave wells #2 and #3 obtain groundwater from the Thorncliffe Aquifer Complex while

Palgrave #4 extracts from Scarborough Aquifer Complex at a maximum permitted rate of 2620

m3per day.

Caledon East - The Region of Peel currently operates three permitted wells in the Caledon East

area, two of which extract water from the Oak Ridges Aquifer Complex and one which extracts

from the Thorncliffe Aquifer Complex. An application to increase pumping rates from the Caledon East wells to accommodate increased residential demand associated with projected

population growth has been made and is the subject of an on-going class environmental

assessment study.

4.2.9 Other water Takings

Golder Associates Limited (GAL) and Marshall Macklin Monaghan (MMM) conducted a

groundwater use survey in the Humber River watershed for the Region of York while Beatty

Associates conducted a similar survey for the Region of Peel. TRCA staff reviewed and consolidated groundwater use information within the watershed based on the MMM and Beatty

Associates reports in addition to the MOE water taking data (TRCA, 2008).

Table 4-2 describes groundwater use on a subwatershed basis. The Humber River State of the

Watershed Report – Surface Water Quantity (TRCA, 2008) summarizes information according

to three different types of water source, “surface”, “groundwater” and “both”. Total annual

groundwater use within the Humber River watershed is approximately 7,340,000 m3/yr.

Municipal drinking water supply accounts for about 47% of the groundwater extraction while

the remaining 53% is split amongst other users (agricultural, domestic, recreational and livestock).

4.2.10 Overall Water Budget

Total recharge to the watershed amounts to about 4.06 m3/s as can be seen on Figure 4-15

(Earthfx, 2007b) while groundwater extraction (as shown in Table 4-2) represents about 0.23

cubic metres per second or about 6% of the total recharge. The remaining recharge of 3.83

m3/s discharges perennially to streams.

Figure 4-15: Humber River Watershed Water Budget

Notes:

m3/s =

cubic m

etres per second; Tim

e period =

average annual; ET =

evapotranspiration; GW =

groundwater; Lateral Inflow =

flow of

groundwater into watershed from adjacent watersheds; Lateral Outflow =

flow of groundwater out of watershed to adjacent watersheds



57

Table 4-2: Total Annual Groundwater Withdrawals, Humber Watershed (TRCA, 2006a)

Subwatershed Purpose Groundwater

withdrawals

(m3/day)

Agricultural 0

Commercial 91

Recreational 130 Black Creek

Sub-total 221

Agricultural 211

Commercial 3,370

Recreational 147

Livestock 233

Miscellaneous 66

Institutional 720

Water supply 3,834

East Humber

Sub-total 8,581

Commercial 109

Livestock 0.5 Lower Humber

Sub-total 109

Agricultural 2,258

Commercial 1401

Recreational 648

Livestock 382

Miscellaneous 71

Water supply 5629

Main Humber

Sub-total 10,389

Agricultural 181

Commercial 591

Livestock 38 West Humber

Sub-total 810

Total withdrawals

20,111

(0.23 m3/s)

The current guidance from the MOE indicates that groundwater withdrawals between 10% and

25% of the total recharge represent a moderate level of stress on the groundwater system and

withdrawals greater than 25% represent a significant level of stress. Accordingly, groundwater

use on a watershed scale is not currently an issue of concern, but given that the extractions are

localized, there will be higher utilization rates on a subwatershed basis. An assessment of

these rates is to be conducted by TRCA as a part of source water protection planning.

Groundwater movement within the deeper aquifer systems along the north western part of the watershed occurs into the Humber River watershed as underflow from the adjacent Credit River

watershed. This deep aquifer might be of interest as a supply of municipal water to Caledon or

Caledon East (Holysh, 2003). Based on the reflection seismic surveys completed near Caledon

East and Bolton, it is interpreted that this aquifer system extends along the buried bedrock

valley from at least Willoughby Road (west of Caledon Village) to the Bolton area in the east.



58

Assuming that the aquifer is continuous along the buried valley, a volumetric flux can be

approximated near the terminus of this basal aquifer system near Bolton.

Assuming an average width of 1,200 m, an average thickness of 20 m, a relatively flat vertical

gradient of 0.002, and a hydraulic conductivity of 10-3 m/s, the volumetric flux at Bolton would

be calculated as:

Q = KiA

Q = 10-3 m/sec x 0.002 x (1,200 m x 20 m)

Q = 0.048 m3/sec or 4,147 m3/day

Groundwater movement into the watershed also occurs along the north eastern boundary from

tunnel channels carved into the deep Scarborough Aquifer Complex (SAC). Further detailed

studies remain to develop a better understanding of the above two possible underflow sources.

4.2.11 Trends in Groundwater Levels

Groundwater level monitoring within the Humber River remains an ongoing activity through the

use of ten monitoring stations accessed through the Provincial Groundwater Monitoring

Network (PGMN).

Table 4-3 lists the ten monitoring stations along with general water level elevation and trend

during the period of measurement for each station. Figure 4-14 shows the monitoring and municipal well locations while the groundwater hydrographs are included in Appendix A.

The measurement and recording of groundwater levels occur by using state-of-the-art Solinst

Levelogger ™ units. The pressure transducer senses the height of the water column with the

digital data stored in a datalogger for temporary storage. Downloading of the digital data can

occur through a dial-up telemetry system or during a visit of TRCA’s field staff to the monitoring

station.

The hydrographs indicate that groundwater level fluctuations in the monitored wells range from

0.05 to 1.5 m over the period of record. These fluctuations are not considered significant.

Declining water level trends were observed in three of the wells, while rising trends are

apparent in five wells and water level remained almost stable in one well.

Groundwater level measurements also occur at supplemental sites such as municipal water

supply and landfill wells. Groundwater level measurements from the three Palgrave municipal

wells (north central part of the Main Humber River) covers the period from 1995 to

2001(Stantec 2004). Although water levels within the municipal water supply wells vary by about 4 m due to their pumping, level recovery occurs following pumping cessation. These

fluctuations are normal. Given these available data, groundwater levels within the Humber

Watershed appear to be stable. It should be noted however, that the dataset is limited in

geographic coverage, number of aquifer units, and the period of record. Therefore, expansion

of the PGMN network and ongoing monitoring are recommended to ensure that the aquifer

water levels are indeed stable.



59

Table 4-3: Water Level Trends

Groundwater Monitoring in the Humber River Watershed

Monitoring Period Groundwater

Elevation Well

Number Aquifer Location

From To From To

Trend

31/07/01 14/10/01 259.8 259.9 Rising

W 060-1 Scarborough

Nobleton

(Deep) 15/10/01 19/08/07 259.6 259.1 Declining

31/07/01 21/05/06 247.2 247.9 Rising

W 061-1 Thorncliffe

Nobleton

(Intermediate) 25/05/06 02/08/07 247.9 247.3 Declining

02/10/03 13/03/06 100.4 100.8 Rising

W 325-1 Scarborough High Park

13/03/06 19/08/07 100.8 100.2 Declining

05/09/03 07/05/04 219.0 220.0 Rising

07/05/04 18/10/04 220.1 219.6 Declining W 327-3 Thorncliffe Bolton (Intermediate)

02/04/05 19/03/07 220.2 218.9 Declining

W 327- 4 Scarborough Bolton (Deep) 09/05/03 19/08/07 219.2 219.9 Rising

W 328-1 Limestone

Bedrock Mono Mills

25/08/03 23/07/07 416.9 416.9 Stable

W 329-1 Oak Ridges Centreville Creek 02/10/03 08/01/07 285.0 286.2 Rising

W 330-1 Thorncliffe Caledon East 10/02/04 02/08/07 281.6 282.1 Rising

12/10/03 18/02/05 176.9 177.3 Rising

18/02/05 04/04/05 176.9 176.0 Declining

20/09/05 27/05/06 177.3 178.3 Rising W 367-1

Oak Ridges/

Mackinaw

Interstadial

Claireville

Conservation Area

27/05/06 20/08/07 178.4 176.9 Declining

W 75-1 Thorncliffe Kortright Centre 09/10/01 19/08/07 175.6 175.7 Rising

Groundwater levels were also measured near the former Town of Caledon landfill site, within the West Humber River watershed for the period of 1992 to 2002. The hydrograph for the two

monitoring wells (installed into upper and lower sand water bearing formations) showed

relatively stable water levels over the time period as indicated in the hydrographs in

Appendix A. From the available measurements, groundwater withdrawals resulting in aquifer

over-pumping or “mining” does not appear to occur.



60

4.2.12 Groundwater Chemistry

The TRCA initiated a quarterly groundwater quality sampling program from the Humber River

watershed PGMN wells. The initial groundwater sampling event undertaken by the MOE

included laboratory analysis of the following parameters:

� Anions;

� Cations;

� Heavy Metals;

� Nutrients;

� Bacteria;

� Chlorinated solvents

� Volatile organic compounds;

� Herbicides; and � Pesticides.

The second and third sampling events, conducted by TRCA personnel in 2004 and 2005,

included chemical laboratory analysis of a reduced parameter list that comprised:

� Anions;

� Cations; and

� Heavy Metals.

The results from first groundwater sampling event were compared initially to the MOE

Provincial Water Quality Objectives (PWQO). Based on these laboratory findings, chemical

testing for pesticides herbicides and volatile organic compounds were discontinued for the

subsequent samplings in 2004 and 2005. The parameter concentrations for the first sampling

event were less than their respective criteria.

The results from the second and third groundwater sampling events were compared to the

MOE Ontario Drinking Water Standards (ODWS) and the PWQO (where applicable). All parameter concentrations were reported below the most stringent applicable criteria.

Table presents the parameter suite per groundwater sampling event for each PGMN well. The

table also shows the aquifer unit from where groundwater is withdrawn, sampled and analyzed.

Cation-anion ionic balance could not be determined from the reported chemical data as the

anions (chloride, sulphate, carbonate and bicarbonate) were not on the list of required

parameters for analyses. The ionic balance should be within 5%. Inclusion of chloride in the

chemical analysis suite of parameters allows for the monitoring of potential road salting

impacts.

Table compares the groundwater quality sampling data for various sampling events from the

PGMN wells. The comparison indicates no significant changes to groundwater chemistry have

occurred during this short monitoring timeframe.

Table 4-4:

Water Quality Sampling Events, PGMN Wells

Event 1

Event 2

Event 3

Event 4

Event 5

Event 6

Event 7

Event 8

Well

Number

Location

Well

depth

(m)

Aquifer

Apr-03

Jun-03

Sep-03

Nov-03

Sep-04

Oct-04

Dec-04

Jan-05

W 60-1

Nobleton (deep)

193

Scarborough

A, B, C,

D,

E,F,G,H,I

A, B, C,

D,

E,F,G,H,I

A, B, C

A, B, C

W 61-1

Nobleton

(Intermediate)

61

Thorncliffe

A, B, C

A, B, C

W 325-1

High Park

13

Scarborough

A, B, C,

D,

E,F,G,H,I

A, B, C

A, B, C

W 327-3

Bolton

(Intermediate)

92

Thorncliffe

A, B, C

A, B, C

W 328-1

Mono Mills

30

Limestone

Bedrock

A, B, C

A, B, C

W 329-1

Centreville Creek

51

ORM/

Interstadial

A, B, C

A, B, C

W 330-1

Caledon East

25

Thorncliffe

A, B, C,

D,

E,F,G,H,I

A, B, C

A, B, C

W 367-1

Claireville C.A.

31

ORM/

Interstadial

A, B, C

A, B, C

W 375-1

Kortright Centre

36

Thorncliffe

A, B, C,

D,

E,F,G,H,I

A, B, C

Notes:

Suite A

General Chemistry

Suite B

Heavy Metals

Suite C

Total dissolved organic/inorganic carbon

Suite D

VOCs

Suite E

Pesticides

Suite F

Herbicides

Suite G

Phenols

Suite H

Chlorobenzenes

Suite I

others

Samples from Events 1 to 4 were analysed by the M

OE laboratory; the remainder were analysed by a private contractor

Table 4-5:

Groundwater Quality Comparisons, PGMN Wells

Notes: a) units in mg/L or as indicated

b) yellow highlight indicates recommended guideline exceeded

c) NT: Not tested

d) repeat result verified

e) ODWS: Ontario Drinking Water Standard (recommended guideline)



63

Elevated iron concentrations above the ODWS value of 0.3 mg/L were reported in:

� Bolton (well W327: 0.752 mg/L).

� Caledon East (W330-1: 0.563 mg/L). and

� Nobleton intermediate (W61-1: 1.327 mg/L).

These elements are not unusual for groundwater, and are natural in origin. Similarly, elevated

concentrations of manganese above the ODWS value of 0.05 mg/L were reported in the Bolton

and Nobleton intermediate wells.

Elevated hardness values (> 200 mg/L) were reported at the High Park and Nobleton

intermediate wells. Water supplies with hardness greater than 200 mg/L are considered poor

but tolerable. These values are the result of natural processes.

Two groundwater sampling events from the High Park well reported elevated total dissolved

solids (TDS) concentrations, ranging from 700 to 900 mg/L, above the ODWS value of 500

mg/L. The term TDS refers mainly to inorganic substances dissolved in water. Generally

speaking, groundwater with limited contact with fresh infiltrating water has higher TDS. The

principal TDS constituents include the inorganic substances such as sodium, calcium,

magnesium and bicarbonates. The effects of TDS on drinking water quality and other uses

depend on the levels of the individual components. Like the previous parameters, the elevated

TDS values are associated with natural processes.

In addition to the PGMN wells, groundwater chemical quality monitoring occurs at twelve

municipal water supply wells within the watershed, six in York Region and six in Peel Region.

Of the twelve wells, six extract groundwater from the Thorncliffe Aquifer Complex, four from the

Scarborough Aquifer Complex and two from ORAC. Chemical water quality of the 12 wells was

reported as meeting the ODWS parameter criteria.

Although there are no serious concerns regarding general groundwater quality within the

Humber River watershed, isolated and localized areas of impacted groundwater quality do exist including the former Chinguacousy Landfill site at the northwest corner of Dixie Road and

Regional Road No. 9.

The Chinguacousy Landfill, operated from 1964 to 1980, incorporated a berm in the late 1960’s

and a leachate collector system in 1975. Groundwater quality impacts were reported in sand

layers both up- and down-gradient of the landfill site. Elevated concentrations of alkalinity,

chloride, sodium, sulphate, nitrate, ammonia, boron, manganese, arsenic, iron and dissolved

organic carbon were reported along with detectable concentrations of volatile and semi-volatile

organic compounds. Groundwater chemistry monitoring data suggests that concentration of dissolved organic carbon, boron, sulphate; iron and chloride in the shallow groundwater

remained fairly stable between 1999 and 2002.

Leachate collected from the landfill toe drain is pumped to the Region of Peel sanitary sewer

system. Some residential properties that surround the landfill in a predominantly agricultural

area were connected to the Region’s municipal water supply system. There remain no known

down-gradient groundwater users in the immediate vicinity of the landfill.



64

An evaluation was performed that assessed potential landfill effects on an adjacent wetland

and tributary to the West Humber River. Nitrates, aluminium, iron, lead, selenium, vanadium

and zinc were reported at levels above the PWQO. Water quality sampling up-gradient and

down-gradient of the wetland suggests that this feature effectively removes organic

contaminants prior to its discharge to the West Humber River tributary.

Humber River State of the Watershed Report - Geology and Groundwater Resources … ·...

Documents

Transcript of Humber River State of the Watershed Report - Geology and Groundwater Resources … ·...