Defining the source area of water supply springs - R. Kreye, M. Wei and D. Reksten November 1996
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Defining the source area of
water supply springs
R. Kreye, M. Wei and D. Reksten
November y 1996
Hydrology Branch
Ministry of Environment, Lands and ParksCanadian Cataloguing in Publication Data
Kreye, R.
Defining the source area of water supply springs
Includes bibliographical references: p.
ISBN 0-7726-2903-X
1. Springs − British Columbia. 2. Water-supply −
British Columbia. 3. Watersheds − British Columbia.
I. Wei, M. II. Reksten, D. III. BC Environment.
Hydrology Branch. IV. Title.
GB1198.4.C3K73 1996 551.498 C96-960161-1Defining the Source Area of Water Supply Springs
Defining the source area of water supply springs
R. Kreye1, M. Wei and D. Reksten,
Hydrology Branch, Ministry of Environment, Lands and Parks
Executive summary
Springs are an important source of water supply in British Columbia (BC), and
yet little is known about their occurrence, source areas, or sensitivity to impacts
from land use activities. An important step in protecting and managing the
spring supply is defining the spring’s source area. Spring source areas can be
identified and defined using topography, geology, water table contours, water
chemistry, spring discharge hydrographs, water balance calculations, and tracer
tests. Due to limited data availability for most springs in BC, a combination of
these techniques will usually need to be employed.
This report presents an approach for defining the source areas of water supply
springs in BC. The approach is based on the use of readily available data and
limited field investigation. In the approach, the investigator compiles and
analyzes data from existing sources and a field investigation to develop an
understanding of the hydrogeology of the spring. From this information the
location and boundaries of the source area can be interpreted. Source area
boundaries are delineated using topographic divides, geologic boundaries, flow
system boundaries identified from water table contours, and feature mapping.
The interpretation is checked using a water balance calculation. The end result
should be technically defensible and include caveats identifying limitations.
While the approach and techniques can be applied to a wide range of spring
types, they will probably be most applicable to springs associated with shallow,
local flow systems, which are common in BC.
The approach and techniques were successfully applied to three community
springs on Vancouver Island. The source areas for the springs were local in
extent, and reasonably well defined by topography. General data limitations
were the lack of spring discharge measurements and hydrogeologic information.
It is recommended that source area investigations be undertaken on springs in
other areas of BC to more comprehensively test the usefulness of the approach.
Information gained from source area can be used to help determine appropriate
management options for protecting the springs from land use impacts.
1 Water Management, Lower Mainland Region, Ministry of Environment, Lands and Parks
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 iDefining the Source Area of Water Supply Springs
Acknowledgments
The licensees of the three springs used for the case studies were greatly
concerned with protecting their water supplies. Jim Lawrence, Obie Olson, Jim
Morgan and Stewart Hollingdrake gave freely of their time, for which we are
grateful. It is hoped that the work presented here provides the information
necessary to ensure their spring-sourced water supplies, as well as all others in
the province, are adequately protected. We would also like to acknowledge the
reviewers of the draft report for their valuable comments. Greg Blaney, Bob
Duncan, Gary Lucas and Jean Wood provided much needed technical support.
Finally, without the support of the Hydrology Branch, especially Karen Rothe
and Jim Mattison, this work would neither have been undertaken, nor
completed.
ii Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
Contents
1 Introduction ..................................................................................................... 1
1.1 Content of report ....................................................................................... 1
2 Spring occurrence and description............................................................... 2
2.1 Development of springs.............................................................................. 5
3 Literature review ............................................................................................. 6
3.1 Techniques for identifying and defining spring source areas...................... 6
4 Identifying and defining source areas .......................................................... 7
4.1 Compile maps, air photos and data............................................................ 13
4.2 Data analysis.............................................................................................. 14
4.3 Develop conceptual hydrogeologic model.................................................. 17
4.4 Delineate source area ................................................................................ 18
4.5 Site investigation ........................................................................................ 20
4.6 Refine conceptual model and source area boundaries .............................. 21
4.7 Evaluate reasonableness of delineated source area.................................. 21
4.8 Write report ................................................................................................ 21
5 Case studies.................................................................................................... 22
6 Conclusions and recommendations ............................................................. 23
7 Glossary........................................................................................................... 25
8 Bibliography .................................................................................................... 27
8.1 Springs ....................................................................................................... 27
8.2 General ...................................................................................................... 27
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 iDefining the Source Area of Water Supply Springs
List of figures
Figure 1. Different types of springs (adapted from Davis and Deweist, 1966) . 3
Figure 2. Effect of topography on groundwater flow patterns and location of source
areas for discharge springs. ............................................................. 5
Figure 3. Approach for identifying and defining source areas.......................... 11
Figure 4. Detailed flow chart of approach for identifying and defining source
areas. ............................................................................................... 12
Figure 5. Relation of catchment area and annual recharge to average spring
discharge (from Todd, 1980) ............................................................ 16
Figure 6. Decision tree identifying appropriate delineation technique for different
geologic media and flow types ......................................................... 19
List of tables
Table 1. Geologic classification of spring types (adapted from Tolman, 1937) 4
Table 2. Techniques for defining source areas................................................ 8
List of appendices
Appendix A. Peter Springs.................................................................................... A1−1
Supply Spring ................................................................................... A2−1
Wheelbarrow Springs ....................................................................... A3−1
Appendix B. Map, air photo and data sources
Data summary forms
Water chemistry parameters ............................................................ B1−1
ii Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
1 Introduction
Springs are an important source of water supply in British Columbia (BC).
Approximately 15 percent of all water licenses in BC are on springs, 105 of
which are for communitu water supplies (waterworks or water users’
communities) and over 6000 for domestic water supplies. These numbers do not
include water licenses on streams that are spring-fed or unlicensed water wells
that are developed in aquifers associated with springs. Springs can comprise the
major or sole source of water supply for larger communities such as Creston,
Spences Bridge and Mill Bay. They also provide high quality water for fish
hatcheries, commercial water bottling industries and are utilized for irrigation
and watering livestock. In many cases, spring waters do not require any
treatment to meet drinking water standards. Despite their importance, there is
limited information available for springs used for water supplies, the location of
their source areas or their sensitivity to land use activities.
The source areas of springs need to be defined to enable protection and
management under BC legislation, such as the Forest Practices Code (FPC), as
well as to support broader Ministry of Environment, Lands and Parks objectives
for the protection of spring-sourced water supplies. Source areas could be
protected as Community Watersheds or Sensitive Areas under FPC legislation.
Preliminary guidelines for management of spring source areas is included in the
FPC Community Watershed Manual. Without knowledge of spring source
areas, protection and management measures cannot be developed or applied.
The knowledge gained from a source area investigation will help guide the
development and application of appropriate protective measures for the spring.
The compilation of data from all investigations will improve our knowledge of
spring-sourced water supplies in BC and help in the development of strategies
for more comprehensive management.
1.1 Content of report
This report is the result of a study designed to determine available methods for
defining the source areas of springs. The report includes background
information on the occurrence and characteristics of springs, techniques that can
be used for locating and defining source areas, and an approach for
investigating and defining source areas. The approach for defining source areas
is based on the use of readily available data and a limited field investigation,
recognizing that, in most instances, investigators may be unable to employ the
drilling and monitoring techniques that are typically required for technically
rigorous hydrogeologic investigations.
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 1Defining the Source Area of Water Supply Springs
Appendix A includes three case studies that demonstrate the application of the
techniques and the approach. The information presented is intended for use by
the professional hydrologist or geomorphologist.
The techniques and approach can be applied to a broad range of spring types
and geologic environments. However, given the generally limited data
availability and proposed level of site investigation, it will be most successful in
shallower flow systems. The report does not address the impacts of resource use
on springs nor does it propose specific protective measures or management
strategies for source areas.
2 Spring occurrence and description
Springs can be classified using a number of different criteria. In the literature
reviewed, spring classifications are usually based on either physical
characteristics or occurrence parameters, such as:
• geology
• magnitude, variation, and permanence of flow
• quality and mineralization of the spring water
• temperature of the spring water.
(Fetter, 1980; Tolman, 1937; Meinzer, 1923)
It is useful to classify springs according to geology, since geology directly
governs spring occurrence and water flow to springs. Most springs in BC can be
classified according to the categories in Table 1. Figure 1 shows conceptual
diagrams of the spring classes.
Springs are naturally occurring discharge features of groundwater flow systems.
Groundwater flow to springs (and therefore the characteristics of the source
area) is governed mainly by three inter-related factors: geology (type,
distribution and permeability characteristics of geologic units), topography
(landforms and relief), and climate (timing and amount of precipitation).
Geology, topography, and climate influence the amount of water that occurs as
surface flow versus the amount that infiltrates into the ground as recharge to
groundwater. All three factors govern how the subsurface flow system develops
and, ultimately, where springs occur. For example, Figure 1-b2 shows that the
nature of the geology (permeable sand overlying low permeability till) and
relief (shallow slope) allows a flow system to develop in the sand unit.
Topography drives the groundwater flow downhill and largely dictates the
occurrence of the spring itself. Climate would influence the timing and amount
of recharge to the flow system and the volume and variability of discharge.
Davis and DeWiest
2 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs Figure 1. Different types of springs (adapted from Davis and Deweist, 1966). Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 3
Defining the Source Area of Water Supply Springs
Table 1. Geologic classification of spring types (adapted from Tolman, 1937).
Type of spring Geologic material Type of porosity Setting
depression unconsolidated primary, occurs where water table
springs sediments intergranular intersects the land surface
contact springs unconsolidated primary, occurs at or near base of
sediments intergranular underlying confining unit
fault/fracture/joint bedrock secondary, occurs along joints,
springs fractures fractures or faults where
they intersect the land
surface
karst springs carbonate bedrock secondary, solution occurs where solution
channels channels developed in
limestone and dolomite
intersect the land surface
lava springs volcanic bedrock primary, flow tubes, occurs where lava tubes,
interbeds and/or interbeds and cooling joints
joints intersect the land surface
(1966) note that “…a vertical or horizontal variation of permeability is the most
common cause of the localization of springs” (p. 63).
The hydrology of a spring is intimately related to the flow system. The
influence of hydrogeology, topography, and recharge dictates the distribution of
hydraulic head within the flow system and, consequently, the flow of water
from recharge to discharge areas and to springs. It is the distribution of
hydraulic head and configuration of the flow system that defines the flow
directions from which the source area for springs can be most directly
determined.
Unfortunately, hydraulic head measurements near most springs in BC are rarely
available for determining hydraulic head gradients and flow directions. In
shallow groundwater flow systems however, which are common in many
terrains in BC, the flow system and flow directions can be inferred from the
local topography and geology. In general, pronounced local relief will affect
shallow flow systems, while regional relief will affect more deeper, regional
flow systems.
The effect of local and regional topography and the concept of shallow and
deeper flow systems are illustrated in Figure 2. Local topography produces
shallow, local flow systems above a regional flow system. Water that enters the
recharge area to a shallow, local flow system discharges at the nearest
topographic low. The source area for springs associated with the shallow
systems can readily be traced uphill within the local topographic high areas.
Springs associated with deeper, more regional flow systems are fed by water
4 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
Figure 2. Effect of topography on groundwater flow patterns and location of source areas
for discharge springs.
that infiltrated across the wider area and from areas farther away, beyond the
local topographic highs.
Geological heterogeneities can similarly have a profound effect on groundwater
flow. For deeper, regional flow systems, in areas of low relief, and in karst
terrains (where flow typically occurs in discrete channels), the identification of
the source area is more complicated and would usually require more detailed
hydrogeologic data.
2.1 Development of springs
Springs range from disperse, low volume seepage to focused high volume
discharge sites. How a spring is developed and the type of waterworks installed
may vary, depending on spring flow and the use for which the water supply is
intended. Common methods of spring development in BC include:
• digging open drainage channels downhill from the spring to divert and
collect the spring flow
• installing drain tiles, pipes, or collection boxes along a seepage face or at a
point of spring discharge
• constructing a gravel back-filled and piped drainage trench along the spring
line, and
• drilling or excavating wells into the spring discharge area.
Supply systems may rely on gravity and natural spring flow or pumps may be
employed.
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 5Defining the Source Area of Water Supply Springs
Although the type of works used to develop a spring generally does not affect
the source area, the works should be included in the overall protected area
specified for the spring. This may include surface water features such as ditches,
ponds or dugouts that are integral to the water supply, or engineered structures
(see Appendix A: Supply Spring and Wheelbarrow Springs). The type of works
may also affect monitoring of spring discharge and water quality, which are
important for determining the characteristics of the spring and source area and
assessment of land use impacts on the spring (refer to Appendix A: Case
Studies).
Where there are a number of associated springs, and where it can be determined
that they are sourced from the same aquifer, it may be appropriate to consider
source area delineation for the group rather than for an individual spring.
Finally, development of other waterworks may affect the source area. For
example, where the aquifer feeding the spring is influenced by pumping wells,
the water table configuration around the wells may change the ambient flow
conditions. This could complicate delineation of the source area, or even change
the source area over time with continued pumping (see Appendix A:
Wheelbarrow Springs).
3 Literature review
The literature review for this study discovered little information directly
addressing the identification and delineation of spring source areas. Some
information is available for karstic springs in Yugoslavia (e.g. Bonacci and
Magdalenic, 1993). There are several case studies for mapping spring sources in
North America (e.g. Munter et al, 1992; Trudeau et al, 1983). Civita (1995)
developed a method for delineating protection zones for springs in the
Mediterranean based on an analysis of considerable historical regional data. Its
applicability to BC has not been assessed.
Risser and Barton (1995) developed a strategy for delineating the recharge area
to wells in fractured bedrock which has potential for use for springs in bedrock.
While the literature review did not reveal any standardized approaches or
methods that could be applied to the range of spring types in BC, it did provide
information on general techniques that can be used for investigating the location
and extent of spring source areas.
3.1 Techniques for identifying and defining spring source areas
There are a number of techniques that can be used to identify and define the
source area of a spring (Table 2). These techniques were compiled from case
study literature, from techniques used for the source area delineation of wells,
and general approaches used for hydrogeologic investigations. Many of the
6 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
techniques can be applied using existing data and limited field surveys. The
techniques use topographic, geologic, and hydrogeologic (e.g., discharge, water
table elevations, water chemistry) data to identify and/or locate either the flow
system or spatial characteristics of the source area.
4 Identifying and defining source areas
This section presents an approach for applying the techniques presented in
Table 2. The approach, as shown in Figure 3 and detailed in Figure 4, is
iterative. Although, in theory, the approach applies to all springs (including
thermal springs), heavy reliance on existing information and the limited scope
of the field investigation suggest that it would be most successfully applied to
springs associated with shallow, local flow systems where local topography and
geology can be used to locate the source area.
The objective of a source area investigation is to define, as closely as
possible, the location and extent of the land area that contributes recharge
to the groundwater flow system that supplies the spring.
To define the source area of a spring the investigator compiles and analyzes
data from existing maps and databases, develops a conceptual model of the flow
system and flow system boundaries, undertakes a site investigation to verify site
specific data, refines and revises the model, and then completes a report
documenting the interpretation. The end result should be a technically
defensible interpretation of the subsurface flow system and flow system
boundaries of the source area, including caveats identifying limitations. Another
outcome of the investigation is an understanding of some of the physical and
use characteristics of the spring and source area, which can support the
development of protective measures.
Variable site conditions and limited information for licensed springs in BC
make it unlikely that any one of the techniques presented in Table 2 would, by
itself, be sufficient to accurately define the source area. However, if the
techniques are used in conjunction, a reasonable determination can usually be
made. In most cases, insufficient hydrogeologic data will limit the
interpretation. It should be emphasized that each investigation will deal with a
unique set of data, and therefore, investigators must remain flexible in their
approach and in what techniques are most appropriately employed.
The case studies in Appendix A illustrate how the techniques and approach are
applied.
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 7Defining the Source Area of Water Supply Springs
Table 2. Techniques for defining source areas.
Technique Description/references Notes
arbitrary designate an arbitrary area • different shapes with specific dimensions may be designated
around a spring to provide (e.g., circular, rectangular, or designated by property
a zone of protection that boundaries)
may include all or part of • is generally not physically based
the actual source area
• may be appropriate for small domestic springs
References: USEPA, 1993 • can be useful as an interim measure if no other option to
outline a protection zone
• precedence: is commonly used to outline source areas for
community wells’ protection where no information is
available
topography surface elevation contours • local topography often controls the direction and gradient of
are used to infer the subsurface flow to springs associated with shallow, near-
direction of subsurface flow surface flow systems
and the location of • in general, pronounced local relief will indicate a local flow
subsurface flow divides system, while areas of low relief would indicate more
References: Kohut, 1985 regional flow systems
• flow divides can be defined at different scales (from small to
large scale maps and air photos down to site level surveys),
accuracy is scale dependent
• assumes flow is perpendicular to the topographic contours
• can delineate a source area directly or by deduction from
delineating adjacent surface watersheds
• may not be accurate for karst terrains, areas of low relief, or
where groundwater pumping has significantly altered the
water table so that it is no longer a subdued replica of the
topography
• precedence: topography has also been used to delineate
groundwater flow regions on the Gulf Islands and outline
source areas for community wells in the Lower Fraser Valley
geology the type, location and areal • the permeability of geologic units and/or differences in the
extent of specific geologic permeability between one unit and another governs the
units is used to define the occurrence of springs and flow to them
source area • quantity and variation in flow, and water quality, are
governed by the characteristics of the geologic units through
References: Bonnaci and
which the water flows
Magdalenic, 1993; Munter
et al, 1992. • identifying the areal extent and depth of different geologic
units and interpreting the geology is a critical step in defining
the source area
• a range of reference sources are available for identifying or
interpreting geology (e.g. surficial geology, landform, terrain
survey, soils and aquifer classification maps; air photos; drill
hole lithologies)
• in fractured and karstic bedrock, the distribution of discrete
fractures and dissolution channels through which water flows
need to be mapped also to delineate the source area
8 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
Technique Description/references Notes
water balance use discharge and • can indicate the size of the source area, but not the location
precipitation data to or boundaries of the source area
calculate the size of the • limited by the availability and accuracy of precipitation and
source area flow data
References: Bonnaci and • compare temporal variation of spring discharge to
Magdalenic, 1993; Munter precipitation to determine if water is derived from
et al, 1992. precipitation
• provides an estimate only
• most useful in context with other techniques
• can provide an indication of largest possible size of source
area
water table the direction of flow and • is a direct method of mapping subsurface flow to the spring
contours location of flow divides are and identifying the location and extent of the source area
inferred directly from water • water table contours can be manually drawn from existing
table elevation contours subsurface water level data points (wells, surface water
and the water table features)
contours are then used to
delineate the subsurface • water table contours can also be derived through modeling,
contributing area or source calibrated to existing data points
area for the spring • accuracy is dependent on scale, number of data points and
how well hydrogeology has been characterized
References: Delin and • accuracy is often limited by the lack of data points and
Almindinger, 1994; Banton insufficient understanding of the site hydrogeology
and Kenrick, 1992.
• in many cases the water table is a subdued replica of
topography and topography can be used to infer subsurface
flow divides that define the source area
• assumes flow is perpendicular to the contours except in:
fractured bedrock, karst bedrock, and other highly
anisotropic geologic units
• water table contours can change seasonally or under the
influence of a pumping well(s)
water chemistry water chemistry can be • provides a gross measure of source area location only: local
used to infer the relative versus regional
age, origin and history of • amount and variation of mineralization (e.g. TDS, specific
the water and give general conductance) are relative indicators of how far and how
indication of the location of deep the water has traveled (water with relatively low TDS
the source area indicates that the source is nearby and likely from
precipitation; seasonal variation in water chemistry would
References: Kohut, 1985;
suggest that water is derived from seasonal recharge)
Gluns and Green, 1994;
Trudeau et al, 1983; Risser • may narrow down potential source areas by unique chemical
and Barton, 1995. constituents of water or by comparison of water chemistry
with other waters
• geology (and land use) can impart a unique chemical
signature in water (e.g. arsenic from some granitic bedrock,
elevated calcium from limestone, nitrates from agriculture or
range land use)
• isotope analysis can indicate physical processes water has
undergone (e.g. evaporation)
• water chemistry sampling should include adjacent surface
waters as well as groundwater sources for comparison
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 9Defining the Source Area of Water Supply Springs
Technique Description/references Notes
spring discharge the recession curve of a • does not identify the location of the source area, only the
hydrograph spring hydrograph is extent and type of protective zones required
analyzed to determine the • guides the design and dimensions of various types of
flow velocity in the spring protective zones for springs of different sensitivities
aquifer; this is used to help
define various zones of • provides an indication of the estimated time of travel (TOT)
protection around the of contaminants
spring • requires a continuous discharge record of the spring, which
is not available in many cases
References: Civita, 1995; • is based on the analysis of springs in the Mediterranean and
Johansson, 1987. has not been applied in BC
• is the only method found that has been specifically
developed for protecting springs
tracers dye or other tracers are • types include: fluorescent or colour dyes, bromide, and
introduced into the up- radioactive tracers
gradient groundwater to • can give direction, rate of travel of flow, the location of point
determine if flow from that sources of recharge (karst systems) and with sufficient data
location forms part of the points, the areal extent of the source area
recharge to the spring
• a comprehensive tracing program requires intensive
References: Risser and sampling and analysis
Barton, 1995.
• use may be limited by regulation or controversy of
introduction into or near drinking water sources
• long travel times of some flow systems may limit applicability
in those terrains
• most useful in rapid flow systems (e.g. fractured bedrock,
karst, high permeability unconsolidated deposits)
• often used to define point source of recharge in karst
systems
10 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
COMPILE DATA
ANALYZE DATA
DEVELOP CONCEPTUAL
HYDROGEOLOGIC MODEL
DELINEATE SOURCE AREA SITE INVESTIGATION
EVALUATE ACCURACY
WRITE REPORT
Figure 3. Approach for identifying and defining source areas.
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 11Defining the Source Area of Water Supply Springs
COMPILE DATA
ANALYZE DATA
characterize topographic setting
• surface water and watersheds
• other springs/groundwater features
• topographic features (gullies, ridges, etc.)
characterize geologic setting
• geologic units and boundaries
• unit materials
• stratigraphy SITE INVESTIGATION
• verify existing data
• acquire new data
characterize hydrogeologic setting • identify local scale features
• aquifer • survey waterworks
• flow from unconsolidated or bedrock unit?
• discharge/precipitation relationships
• water balance
• water table elevations/contours
• water chemistry
identify land use setting
• land use features and boundaries
• vegetation (recharge/discharge features)
CONCEPTUAL MODEL
• flow shallow or deep?
• flow local or regional?
• flow through which geologic deposits?
• discrete or porous flow?
• sources of recharge?
• topography reflection of water table?
• flow boundaries same as geologic boundaries?
DELINEATE SOURCE AREA
• topographic divides
• geologic boundaries
• flow system mapping
• feature mapping
EVALUATE ACCURACY
WRITE REPORT
Figure 4. Detailed flow chart of approach for identifying and defining source areas.
12 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
4.1 Compile maps, air photos and data
The objective of data gathering and analysis is to develop a site specific
understanding of how the spring occurs and what physical factors control flow
to the spring. Data should be shown on appropriate maps and cross-sections.
While the final source area boundaries should be presented on a 1:20 000 TRIM
base, larger scale base maps may be appropriate, especially if the spring source
area is highly localized (refer to map figures in case studies).
Every effort should be made to acquire data from the variety of sources
available, since interpretation will often rely heavily on existing data. Data
sources include various ministry databases (e.g. WLIS, SEAM, and WELL),
other government agencies (Ministry of Health, Ministry of Forests, Ministry of
Transportation and Highways), forest licensees, and water purveyors. The site
investigation will also generate additional data. Appendix B includes a
summary of data sources, and forms that summarize data types.
The following features should be identified and mapped:
• the water supply spring(s)
• other spring(s)
• local and regional surface water features and their watersheds (lakes, ponds,
streams, etc.)
• other surficial features (gullies, ridges, depressions, topographic divides, etc.)
• distinct forest cover and vegetation types
• geologic units and boundaries (surficial geology, bedrock geology, soils,
landforms, etc.)
• land use activities (roads, mines, gravel pits, dumps, clear cuts, range use,
agricultural use, etc.)
• wells and other drill holes
• groundwater level elevations
• delineated aquifers
• waterworks
The following data should be compiled:
• spring discharge
• water chemistry
• precipitation records
• characteristics of geologic units (material, origin, etc.)
• well lithologies and aquifer materials
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 13Defining the Source Area of Water Supply Springs
4.2 Data analysis
The mapped and compiled data is analyzed to develop an understanding of how
the spring occurs, possible sources of recharge, and where flow to the spring
may originate. From this information a conceptual model of the flow system
and flow system boundaries associated with the spring is developed. Data
analysis identifies the topographic, geologic, hydrogeologic and land use
settings of the spring, and provides information on the following:
• surficial relief (topography)
• geology (permeability, stratigraphy)
• water table elevation contours for the aquifer supplying the spring
• water balance and discharge / precipitation relationships
• water chemistry
Topography
Topography often reflects the underlying water table surface and can be used to
infer subsurface flow directions and flow divides, especially for shallow flow
systems. Two indicators of whether a spring is associated with a shallow flow
system are: 1) where the seasonal variation in discharge generally correlates
(with a lag time period) with seasonal precipitation patterns; and, 2) where the
water quality (as reflected by the specific conductance or total dissolved solids
(TDS) (e.g. mineralization)) is relatively fresh (as compared to rainwater) and
fluctuates seasonally. Spring discharge from deep flow systems may show little
seasonal variation in flow or quality.
The degree to which the water table reflects surface topography can be checked
by plotting known or inferred water table elevations against surface elevations
at those points, for as many points as possible in the area (see Figure 7,
Appendix A: Wheelbarrow Springs). A positive correlation indicates that water
table elevations reflect surface topography. Subsurface flow is assumed to be
perpendicular to surficial contour lines. Groundwater divides are assumed to
coincide with topographic divides.
Geology
Geology and stratigraphy (presented in the form of fence diagrams, cross
sections, and isopach maps) identify the location and extent of the type of
materials or the aquifer through which groundwater flow to the spring occurs.
The porosity, permeability and/or differences in permeability between different
geologic units help determine the factors controlling spring occurrence, rate of
flow, extent and type of recharge zones, and the potential sensitivity of the
spring to impacts.
14 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
Groundwater flow in different geologic materials occurs as either porous flow
or discrete flow. Porous flow generally occurs in unconsolidated materials or
intensely fractured bedrock, and discrete flow in discontinuous fractures in
bedrock, along faults and in solution channels (karst bedrock). As geologic units
are distinguished by similar properties (e.g. rock type), including hydrogeologic
properties, the mapping of geologic units is important for defining the flow
system, the aquifer through which flow occurs, and the extent of the source
area.
Water table contours
In unconsolidated deposits and intensely fractured rock, water table elevations
and contours reflect groundwater flow directions and, therefore, direction from
where spring water originates. Where water table contours are available or can
be developed, they are a direct method of identifying the source area
boundaries. Water table elevations may be identified on well records or can be
taken directly from water level measurements in wells. They can also be
inferred from the elevation of surface water features, other springs or seeps, or
from diagnostic vegetation associated with groundwater discharge sites. In
shallow flow systems, the water table is often assumed to be a subdued replica
of surface topography, and as such, water table contours would generally follow
topographic contours.
Source areas for springs can be delineated by drawing flow lines from the spring
perpendicular to the water table contours upgradient, similar to how watersheds
are delineated for surface water sources.(see Appendix A: Wheelbarrow Springs)
Water balance
A water balance provides an estimate of the size of the source area given the
spring discharge and amount of recharge in the source area. It is usually
calculated on an annual basis. A general water balance equation for a spring
source area is:
Q + W = A (P − ET + ∆S)
where: Q = spring discharge
W = other discharge in source area (e.g. springs, pumped wells, surface
water flow)
A = source area
P = total precipitation
ET = evapotranspiration
∆S = change in storage
If we consider discharge from year-to-year, ∆S can be assumed to be zero if
conditions remain constant over a number of years. Where other sources of
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 15Defining the Source Area of Water Supply Springs
discharge, such as well pumping, are absent, W can also be assumed to be zero.
Spring discharge is obtained from discharge records, observation, or anecdotal
information. Precipitation is estimated from nearby climate station data adjusted
to reflect source area conditions, or from regionalized estimates shown on
isohyetal maps. Evapotranspiration can be calculated from climate station data
using the Thornthwaite method, isohyetal maps of evaporation, or from climate
station evaporation data. The size of the source area can then be calculated
from:
A (km2) = Q (dam3)
P (mm) − ET (mm)
(m3/s ✕ 31 540 = dam3 for annual amounts)
(dam3 [cubic decametres])
This relationship between source area, discharge and recharge is demonstrated
in Figure 5.
10 000
annual recharge
0.1mm
square kilometres
1000
1 mm
Source Area of Spring
10 mm
100
100 mm
1000 mm
10
315 mm
100 ha
100
hectares
10 L/s
10
0.1 1 10 100 1 10
L/s m 3/s
Spring Discharge
Figure 5. Relation of catchment area and annual recharge to average spring discharge
(from Todd, 1980).
16 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
Water chemistry
Water chemistry, including seasonal variation, can be used to infer the origin
and relative age of water. For example, a spring may show distinct seasonal
variability in chemistry that correlates with the seasonal precipitation
fluctuation (with a lag time period), indicating that the spring is recharged
directly by infiltration of precipitation.
Spring water chemistry contains chemical, isotopic, and thermal signatures
which may reveal flow paths and history. For example, the amount of total
dissolved solids (TDS), in the spring water compared to the chemistry of nearby
surface water, rain water, and well water may indicate the relative subsurface
residence time and distance groundwater has traveled before discharging as a
spring. Spring water with low TDS (slightly higher than rain or surface water)
would suggest that the spring water is from infiltration of local precipitation or
fresh surface water and that the source area is of local rather than regional
extent.
The presence of elevated levels of minute chemical constituents, such as
arsenic, fluoride, organic acids, and nitrate, in the spring water provides clues to
the origin of the spring water and helps define the location of the source area by
association with specific geologic units or land use activities. In the semi-arid
interior of BC, Kohut (1985) used the isotopic character of spring water to
deduce that the source area for Shaughnessy Spring at the Summerland Trout
Hatchery included infiltration from surface drainage sources because the spring
water showed isotopic evidence that the water had undergone evaporation prior
to infiltrating to the aquifer.
The specific constituents tested for should be determined in context of the
geologic and land use environment of the spring. A common minimum field
analysis would include: TDS (or specific conductance), temperature, pH and
nitrate-nitrogen. Typical parameters for laboratory analysis are included in
Appendix B. Comprehensive historic lab chemistry for a particular community
spring may also be available from Ministry of Health’s WSACS database.
4.3 Develop conceptual hydrogeologic model
Developing a conceptual hydrogeologic model is a natural progression from
data analysis. Data analysis should give an understanding of how the spring
occurs, the physical factors governing flow to the spring, the possible sources of
recharge, what additional information would be required to clarify the
interpretation or distinguish one interpretation from another, and which
technique(s) best support source area boundary delineation. The detail of the
conceptual model will be governed by data availability, however, the process of
developing the model helps to identify additional data needs or limitations of
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 17Defining the Source Area of Water Supply Springs
the final interpretation. In developing the conceptual model, the following
questions should be answered:
• What and where are the potential sources of water that supply the spring?
• How and through what geologic unit might water flow to the spring?
• What physical factors (e.g. topography, geology) control flow to the spring?
• Does the water chemistry suggest a local or regional, shallow or deep flow
system?
• Does spring discharge or water temperature variability suggest a deep or
shallow flow system?
• Does water chemistry suggest what geologic environments or land use areas
the flow system may be associated with?
• Does the water balance suggest a large or small source area?
• Are there identifiable recharge and discharge areas?
• What techniques might be suitable for delineating source area boundaries?
• What information is missing and required to confirm the interpretation and
delineate boundaries?
• Is there more than one plausible interpretation of the source area?
• What additional information is required to test whether one interpretation is
more likely than another?
The conceptual model can be illustrated diagramatically or through maps and
cross-sections. Rationale supporting the conceptual model, and limitations,
should be clearly documented.
4.4 Delineate source area
Inferred groundwater flow directions and flow divides mark the location of
source area boundaries. Flow system boundaries are identified using:
• water table elevation contours
• topographic divides
• geologic unit boundaries
• feature mapping (e.g. sinkholes, faults, etc.).
Figure 6 provides guidance on the most appropriate technique for different
types of flow systems. The justification for what techniques are used to
delineate the source area boundaries is derived from data interpretation and the
conceptual model of the spring.
18 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
Of the techniques presented in Table 2, the use of topography, geology, and
water table elevation contours, or a combination of these techniques would be
most common. Water table elevation contours are usually not available or may
be difficult to map without a sufficient number of data points. Where it can be
demonstrated that topography reflects the water table surface (see section 4.2),
it may be appropriate to use topographic contours to identify inferred flow
divides. Where flow occurs in specific and identifiable geologic units, the
geologic unit boundaries can also be used to help outline source area
boundaries.
Feature mapping, utilizing tracers and field mapping, can be employed for
refining source area boundaries or for delineating source area boundaries in
discrete flow bedrock and / or karstic systems. Tracers are most effective where
the source area is very localized and flow to a spring is sufficiently rapid (i.e.
travel times of days or weeks rather than months or years) for tests to be carried
out. The use of certain tracers may be controversial, especially when introduced
into or near active drinking water sources.
flow medium flow type flow system delineate
characteristics boundaries using
Is the flow system
shallow and the water topographic
table a reflection of divides
the topography
f ?
unconsolidated Is the flow system water table
deposits; intensely porous deep or regional in elevation
fractured bedrock nature? contours
Are any flow
boundaries consistent geologic
with geologic unit unit
boundaries? boundary
Is flow confined to a feature
fractures faults discrete limited number of mapping
conduits
discrete channels?
Figure 6. Decision tree identifying appropriate delineation technique for different
geologic media and flow types.
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 19Defining the Source Area of Water Supply Springs
4.5 Site investigation
The site investigation should verify site conditions, gather additional data to
further characterize the springs and source area, identify local scale features,
and survey the waterworks. In many cases, the mechanism of spring occurrence
will not be obvious from an office assessment and can only be determined by
site investigation. A site visit also enables spring works to be documented and
locations identified for monitoring spring flow and raw water quality. The site
visit should confirm and/or support revision of the conceptual model.
Site investigations are critical for springs with highly localized source areas.
Site surveys should identify local features that may indicate the nature, location
and extent of the flow system. Such features as intermittent or ephemeral stream
sections, hydrophytic vegetation, seepage faces, and locally defined topography
which do not show up on contour maps or air photos are important in
delineating the source area boundary. For example, at Peter Springs (see
Appendix A) the nature of the flow system could only be determined by
mapping site features. This included digging into the spring to identify what
materials flow was discharging from, identifying the spring discharge area from
the presence of ferns and other hydrophytic vegetation, and field mapping local
topography that defines the source area upslope of the spring.
In bedrock units, it may not always be apparent if flow is discrete or porous at
the spring site. Field mapping should identify other springs or seepage features
to verify if intense fracturing (porous flow) is evident, or verify the existence of
individual fracture, fault or conduit features.
Site-specific maps may be required to accurately identify and depict source
areas. Information that should be obtained from the site investigation includes:
• locating the spring site and predicted source area
• verifying the location and characteristics of landforms and surface water
features
• verifying or identifying the location and characteristics of geologic units and
geologic features
• identifying significant local scale landforms, water courses, land use, and
diagnostic vegetation (recharge and discharge sites)
• surveying and identifying the components of the waterworks
• identifying monitoring sites for discharge and water quality sampling
• taking water chemistry samples and discharge measurements (estimate if no
other options available) from the spring and other water sources, as required
• interviewing water purveyor / licensee for access to data, spring history, and
anecdotal information.
20 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
4.6 Refine conceptual model and source area boundaries
Site investigation information should be analyzed and used to support or revise
initial interpretations, the conceptual model, and the location of the source area
and its boundaries. In some cases a number of iterations of the definition
process, including various types of site surveys that build on previously
acquired information, may be required to arrive at a final interpretation.
4.7 Evaluate reasonableness of delineated source area
There is always a degree of uncertainty associated with delineation of a spring
source area because complete information is never available. Ideally, the
accuracy of the delineated source area can be evaluated by conducting more
extensive site characterization. This, however, is often not practical or
necessary. It may be sufficient to conduct further investigation only for those
factors or specific areas which were uncertain, or which are vital to the
interpretation.
The reasonableness of the interpretation should checked by reviewing the
consistency of results between the different techniques that were employed. For
instance, if water chemistry indicates that the flow system is likely deep and
regional, then a locally defined source area using topography would not be very
accurate. The water balance provides an estimate of the size of the source area
and can be used to evaluate the accuracy of source areas defined using
topography, geology or water table contours. A review would be necessary if
the size of the defined source area is inconsistent with what can be justified
from the water balance.
In some cases, the uncertainty may be so great that a source area cannot be
reasonably defined. In these cases, the results of the assessment should identify
what further information is required and make recommendations on how this
information can be obtained. As an interim measure, the designation of some
arbitrary fixed area may be appropriate to provide a measure of protection.
4.8 Write report
It is important to document the assessment for each spring source area so that it
can be reviewed and defended. At a minimum the following information should
be included in the report:
• site location
• spring and waterworks description
• topographic setting and nearby surface water features
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 21Defining the Source Area of Water Supply Springs
• geologic setting
• hydrogeologic setting and groundwater conditions
• interpretation of spring source area
• spring source area description and delineation
• potential impacts to the spring water supply
• summary and conclusions of assessment
• references
The case studies in Appendix A show the level of detail and content of spring
assessment reports.
5 Case studies
Assessments were completed on three community spring sources on Vancouver
Island: at Cowichan Lake (Peter Springs); Courtenay (Supply Spring); and Mill
Bay (Wheelbarrow Springs) to determine if spring source area boundaries could
be delineated using the approach and techniques presented in this report. These
springs were chosen because of their different geographic settings and
differences in availability and type of data. The case studies are presented in
Appendix A.
The results indicate that, for these springs, source areas can be identified and
defined with reasonable confidence using the described techniques and
approach, despite the variations in data type and availability. Data for each
spring ranged from limited (Peter Springs) to comprehensive (Wheelbarrow
Springs). The source areas for the springs are local in extent, ranging from
approximately 1 hectare for Peter Springs to 40 hectares for Supply Spring.
Each of the springs are potentially at risk from current or proposed land use
activities within the defined source areas.
A major reason source areas were able to be defined is that in each case
topography could be used to approximate the direction of subsurface flow to the
springs. However, geological interpretation, water chemistry, and discharge
data were also important and provided a better understanding of spring
occurrence and the nature of the source area. As well, none of the assessments
could have been completed with adequate confidence without the site
investigations. This is especially true for Peter Springs, where the source area
was defined on-site rather than at the map scale level.
The assessment of Wheelbarrow Springs illustrates that, unlike surface
watersheds, spring source areas may change over time. If significant pumping
of wells in the source area occurs, the water table configuration upslope of the
springs could change, consequently altering source area boundaries.
22 Hydrology Branch, Ministry of Environment, Lands and Parks, 1996Defining the Source Area of Water Supply Springs
While the success of the spring assessment relies to a great extent on compiling
available information, it was found that the data sources often did not contain
adequate or appropriate information for supporting hydrologic investigations.
For instance, the water license files and water information data base (WLIS)
contain mostly administrative information, and the Engineers Report that
accompanies license applications is usually limited. Even so, information from
the files and database helped establish an understanding of the waterworks and
provided relevant historical information. In some cases discharge estimates
were included.
The most important data that are generally not available are discharge
measurements or estimates, or the date and method of measurement. Discharge
measurements support the interpretation of the location, nature and size of the
source area and are required for the water balance calculation. The results of
these analyses depend on the availability and accuracy of the discharge data.
The geographic and hydrogeologic settings of the three case studies represent a
limited spectrum of types of springs that may be encountered in BC. How
typical these springs and source areas are is unknown. The applicability of the
approach to other spring types and to other geographic areas of the province
needs to be determined.
6 Conclusions and recommendations
The approach presented here for defining the source area of water supply
springs depends on the compilation and analysis of existing data and site
investigation. The case studies indicate that the approach can be applied and
reasonable determinations made. The approach is limited by the availability of
existing data, primarily discharge measurements and hydrogeologic
information.
The absence of information on springs in BC is an indication of the amount of
work that needs to be undertaken before effective management and protection
of spring-sourced water supplies will become possible. The uncertainty
associated with defining source areas using limited information also indicates
the importance of monitoring land use activites in source areas and assessing
their impacts on the spring supply. The results of this report indicate that a
number of areas require further research or development:
• improved documentation of spring hydrologic characteristics during the
licensing process and inclusion of this information in appropriate data bases
Hydrology Branch, Ministry of Environment, Lands and Parks, 1996 23You can also read
