Pontus Andersson Hydrogeological investigation for the PEGASUS

27 Pages·2010·3.67 MB·English

Hydrogeological investigation for
the PEGASUS project, southern
Skåne, Sweden
Pontus Andersson
Examensarbete i geologi vid Lunds universitet -
Kvartärgeologi, nr. 259
(30 hskp/ECTS)
Institutionen för geo- och ekosystemvetenskaper
Enheten för geologi
Lunds universitet
2010
Hydrogeological investigation for the
PEGASUS project, southern Skåne,
Sweden

Master Thesis
Pontus Andersson
Department of Earth and Ecosystem Sciences
Division of Geology
Lund University
2010
Content
1 Introduction ......................................................................................................................................................... 5
1.1 Background 5
1.2 Pesticides 5
1.3 Purpose 5
1.4 Aims 5
2 Catchment area .................................................................................................................................................. 6
2.1 Area discription 6
2.2 Geology 6
2.3 Hydrogeology 6
3 Methods................................................................................................................................................................ 7
3.1 Mapping of existing wells 7
3.2 Well drilling 8
3.3 Grain size analysis 8
3.3.1 Sieving 8
3.3.2 Hydrometer 9
3.4 Hazen’s method 9
3.5 Slugtest 9
3.6 Percolation tube test 10
3.7 CFC analysis 10
3.8 Water balance 10
4 Results ............................................................................................................................................................... 11
4.1 Geology 11
4.1.1 Geological profiles from the catchment area 11
4.1.2 Grain size analysis 12
4.2 Hydrogeology 13
4.2.1 Aquifers 13
4.2.2 Conductivity 13
4.2.2.1 Well location 1 14
4.2.2.2 Well location 2 14
4.2.2.3 Well location 3 15
4.2.3 Hydraulic gradiant and goundwater divides 14
4.2.4 Water age results 15
4.2.5 Water balance 16
4.2.6 Areas of recharge 17
4.3 Concluding results 17
5 Discussion .......................................................................................................................................................... 17
5.1 Groundwater level and uncertainties 17
5.2 Geology 18
5.3 Aquifers 18
5.4 Hydrogeological properties 18
6 Conclusions ....................................................................................................................................................... 18
7 Recommendations ............................................................................................................................................. 19
8 Acknowledgements .......................................................................................................................................... 19
9 References .......................................................................................................................................................... 19
Appendix A, Well information
Appendix B, Sieving and hydrometer analysis results
Appendix C, Precipitation and runoff
Cover Picture: Picture over the investigated area, taken by C. Sparrenbom from well location 1 towards well location 2 and 3
NOTE: names of villages and rivers have been excluded as a request from SLU due to their ongoing research in the
area.
2
Hydrogeological investigation for the PEGASUS project,
southern Skåne, Sweden

PONTUS ANDERSSON
Andersson, P., 2010: Hydrogeological investigation for the PEGASUS project, southern Skåne, Sweden. Master
thesis in geology at Lunds Universitet. Nr. 259, 24 pp. 30 ECTS credits.
Abstract: SLU (Swedish University of Agricultural Sciences) have had a project ongoing in a catchment area in
southern Skåne for 20 years where they study how pesticide occurrence in surface waters correlate to the sort and
amount used on the agricultural fields. A new project started by SGI (Swedish Geotechnical Institute) called
PEGASUS (PEsticide occurrence in Groundwater, A Study for sustainable Use in Skåne) has begun an investiga-
tion in the same catchment to study the pesticide behavior and effects in the deeper groundwater. This paper is a
geological and hydrogeological investigation of the catchment area for the PEGASUS project.

The catchment area is located in a valley that is partly formed by a river and partly by faulting. The river’s course is
anthropogenically modified by a culvert system draining the agricultural fields and the river emerges first in the SE
part of the catchment area. The valley sediments consist of an upper and lower glaciofluvial sand divided by a silty
clay layer. The surface sediments consist of a clayrich till which makes up 90 % of the surface sediments, the re-
maining 10 % consists of glaciofluvial sediments and postglacial sediments.

There are two groundwater divides within the investigated aquifer, one in the northern part of the catchment area
and one to the west of the catchment area. The groundwater gradient follows the surface water gradient which is SE
and E towards the river. The recharge from surface water to the upper aquifer is low meaning that recharge likely
occurs during heavy precipitation periods. The average age of the groundwater is c. 40-60 years. The hydraulic con-
ductivity was calculated based on three different methods, Hazen’s method, slugtest and percolation tube test. The
results varied between these methods but the general hydraulic conductivity of the upper aquifer ranges from 2*10-4
m/s, for the coarsest sediments, to 2*10-7 m/s, for the finest sediments.

Keywords: South Sweden, South Skåne, geology, hydrogeology, PEGASUS
Pontus Andersson, Department of Earth and Ecosystem Sciences, Division of Geology, GeoBiosphere Science Cen-
tre, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden. E-mail: [email protected]
3
Hydrogeologisk undersökning för PEGASUSprojektet, södra
Skåne, Sverige
PONTUS ANDERSSON
Andersson, P., 2010: Hydrogeological investigation for the PEGASUS project, southern Skåne, Sweden. Examen-
sarbeten i geologi vid Lunds Universitet. Nr. 259, 24 pp. 30 ECTS credits.
Sammanfattning: SLU (Sveriges Lantbruksuniversitet) har ett pågående projekt i ett område i södra Skåne sedan
1989 där de studerar hur bekämpningsmedel i åar korrelerar med vad som används på åkrarna. Ett nytt projekt, ini-
tierat av SGI (Statens Geotekniska Institut), kallat PEGASUS (PEsticide occurrence in Groundwater, A Study for
sustainable Use in Skåne) har påbörjat en undersökning i samma område för att studera hur bekämpningsmedel
uppför sig och påverkar grundvattnet. Detta arbete är en geologisk och hydrogeologisk undersökning av området åt
PEGASUS-projektet.

Området ligger i en dalgång som dels är formad av en flod och dels av förkastningar. Floden har sin början i sydöst-
ra delen av området. Dalgången är fylld med glaciala flodsediment. De glaciala flodsedimenten kan delas upp i två
sedimentenheter, en övre enhet och en undre enhet. Dessa delas av ett lerlager som ligger mellan dem. De översta
sedimenten består till 90 % av leriga moräner och de övriga 10 % består av glaciala flodsediment och andra sengla-
ciala sediment.

Där finns två stycken grundvattendelare i området som skärmar av det undersökta magasinet från andra närliggan-
de, den första grundvattendelaren ligger norr om området och den andra väster om området. Grundvattnet i det övre
magasinet har en gradient och ett flöde mot ån. Från vattenbalansberäkningar kan vi konstatera att akvifären fylls
på med mycket lite vatten uppifrån och att påfyllning troligen sker vid perioder av kraftigt regn. Vattnets ålder är c.
40-60 år. Den hydrauliska konduktiviteten beräknades med hjälp av tre olika metoder, Hazen’s metod, slug-test och
perkolationsrörs-test. Resultaten varierade mellan de olika metoderna men den generella hydrauliska konduktivite-
ten varierar från 2*10-4 m/s, för de grövsta sedimenten, till 2*10-7 m/s, för de finaste sedimenten.

Nyckelord: Södra Sverige, Södra Skåne, geologi, hydrogeologi, PEGASUS
Pontus Andersson, Institutionen för geo- och ekosystemvetenskaper, Enheten för geologi, Centrum för GeoBiosfärs-
vetenskap, Lunds Universitet, Sölvegatan 12, 223 62 Lund, Sverige. E-post: [email protected]
4
1 Introduction decreasing with depth mostly as a result of a decrease
in microbial populations (Steele et al. 2008).

The rates at which pesticides and their metabo-
1.1 Background
lites move through the soil are also related to their
There are numerous factors controlling pesticide leak-
tendency to adsorb to soil particles and geologic mate-
age to groundwater, e.g. the hydrogeological proper-
rials (Steele et al 2008).
ties of the sediment, pesticide properties and land use.

Soils with a high sand content and a low biomass have
1.2 Pesticides
a low pesticide degration rate and high pesticide mo-
Pesticides are chemicals used to eliminate or remove
bility. The pesticide mobility is, apart from its chemi-
harmful insects, vegetation, fungi and microorganisms.
cal characteristics and the microbial activity in the soil,
The pesticides used in Sweden have to be approved by
related to groundwater velocities, which in turn are
the Swedish Chemicals Agency (Kemikalie-
related the grain size distribution and porosity of the
inspektionen) (Axelsson 2003).
sediments. Sediments with high content of gravel and
A pilot study made by Hagerberg (2007) con-
sand yield a high effective porosity whereas sediments
cludes that over 40 % of wells reaching the bedrock
with high clay content have a low effective porosity
and 50 % of wells withdrawing water from unconsoli-
(Axelsson 2003).
dated sediments, within high agricultural usage areas,
Another important factor is the thickness of the
exceed proposed minimum values (as proposed by
unsaturated zone (the zone between the groundwater
SGU:FS:2008:2) for one or more of the following sub-
surface and the ground surface), which control the
stances; chloride, sulphate, nitrate, ammonium, cad-
time it takes for a pesticide to reach the groundwater
mium, mercury, arsenic, lead or pesticides. 30 % of
zone. The groundwater level varies naturally through-
these wells exceed the environmental goal for good
out the year, affecting the thickness of the unsaturated
groundwater quality.
zone (Axelsson 2003).
A similar local investigation has been carried
Kreuger (1998) has since 1989 kept a pesticide
out by Leander and Jönsson (2003). They investigated
transport project running in a catchment area in south-
pesticide concentrations in Alnarpsströmmen, which
ern Skåne. The project focuses on pesticide concentra-
crosses western Skåne from around Barsebäck in the
tions within the surface water and sediments in rela-
NW to Skurup in the SE . Their result showed that
tion to agricultural pesticide usage. Kreuger and col-
65% of the upper part of the groundwater table was
leagues (Krueger 1998, Kreuger et al. 1999) have
contaminated with pesticides. Seven out of seventeen
found a correlation between the amount of agricultural
samples contained more than one type of pesticide.
pesticide used and the concentrations found in stream
Pesticides affect the environment in numerous
water.
ways, both direct and indirect. Direct effects could be
This work is the first part of a new project, in
high toxicity with a direct affect on human health or
which we study pesticide behaviour and transport to
water and soil ecosystems and the environment in a
and within the deeper groundwater of the catchment
short time span. Indirect effects are longlasting and
area. The project is called PEGASUS (PEsticide oc-
affect the environment or humans slowly and the ef-
currence in Groundwater, A Study for sustainable Use
fects are not visible until after a long time (Axelsson
in Skåne) and is governed by SGI (Swedish Geotech-
2003).
nical Institute) in Malmö in cooperation with Lund
A study made by Laino 2009 relates the in-
University. The project will last for three years and
creased use of pesticides in USA with the increase of
was initiated during the summer of 2009.
Alzheimer’s disease. The result points towards a rela-
A number of similar studies have been carried
tion but more investigation is needed for a concluding
out over the past five years in the United States (Steele
result.
et al. 2008) and they have shown pesticide contamina-

tion of the groundwater. In the presented investiga-
1.3 Purpose
tions, the pesticides have been applied on agricultural
land and contaminating the groundwater as a result of The purpose of this work is to give a geological and
downward movement and subsurface transport. Detec- hydrogeological overview of the catchment area used
tion of pesticides in the groundwater is a difficult task by Kreuger et al. (1998, 1999) for a better understand-
due to numerous factors e.g. the multitude of pesti- ing of the aquifer systems in the area, the groundwater
cides, the intensity of pesticide application, time of flow direction and velocities. This is the first step in a
application in relation to major recharge events of the larger investigation about sorption, degradation and
aquifers, frequency of precipitation and irrigation, wa- movement patterns of pesticides in the aquifer system.
ter table depth, properties of the soils and management
1.4 Aims
of the land. Transformations of pesticides have a rela-
tively large impact on the detection rates. This is due This work aims to:
to pesticides degradation, resulting in an undetectable  Describe and characterize the geology in the
parent compound. The rate of transformation has been catchment area.
found to be largest in the upper soil root region and  Describe and characterize the different aquifers
5
in the catchment area (number of aquifers, type faulting of the area the limestone has an undulating
of aquifers and how do they interact?) upper boundary which is also visible through the un-
 Describe groundwater flow direction and ve- dulation in the landscape. SW of Romeleåsen the Cre-
taceous limestone is overlain by Tertiary Dan lime-
locities in the different aquifers
stone (Daniel 1992).
 Calculate the water balance and aquifer re-
The limestone in the catchment area has an
charge of the catchment area;
upper boundary at depths that ranges from 10 to 80
 Participate in investigating the age of the meters, the depth of the lower boundary is unknown
groundwater at different depths. (SGU).
Two till types are present in the catchment area,
2 Catchment area the dominating one is coarse clayey till (fig. 1). Coarse
clayey till has a clay content of 15 – 25 %. The sec-
ond till type is clayey sandy silty till (fig. 1) with a
2.1 Area description
clay content of 5 – 15 % making it very similar to the
The investigated area is located in southern Skåne.
coarse clayey till. Both till types have a low content of
There is an undulating topography throughout the area
gravel and boulders. Limestone can be found in the till
with an average height of 45 m above sea level (a.s.l.).
in areas where the upper limestone boundary is located
The area is dominated by agricultural activities
close to the surface. Intermoraine sediments in the area
(Svensson 1999).
are located at a general depth of 10 – 20 meters. The
The dominating quaternary deposits within the
thickness of the intermoraine sediments can reach up
catchment area is till. The total catchment area is 9
to 35 meters in the south and thins out towards the
km2 where arable land makes up 95% of the area. The
north. (Daniel 1992).
surface soil contains on average 2.5 % organic matter.
Glaciofluvial sediments are few in the area and
Apart from the cultivated crops during the growing
are mostly concentrated to low relief areas (fig. 1). The
season, the vegetation coverage is scarce and concen-
composition is the same as for the intermoraine sedi-
trated to gardens and agricultural borders (Kreuger et
ments (Daniel 1992).
al. 1998).
Glaciolacustrine sediments are also few within
The regional climate of the area is maritime due
the area and are concentrated to the W of the catch-
to westerly winds and the vicinity of the Baltic Sea.
ment area in the N-S directed valley (Daniel 1992,
The annual mean temperature of the area was 7.2o C in
1988) (fig. 1). The composition of sediments varies
1961-1990 (Kreuger et al. 1998).
between clayey silt and sand (Daniel 1992, 1988).
During the late 1950’s, the xeisting ditches in a
Postglacial sediments are few within the catch-
large part of the area were replaced with a culvert sys-
ment and are located in the same area as the glacioflu-
tem. 40 % of the field area is drained through this cul-
vial and ice lake sediments (Daniel 1992, 1988) (fig.
vert system and the remaining parts are drained
1).
through tile installations that follow the natural drain-

age routes. These systems discharge the water into a
2.3 Hydrogeology
stream which can be seen in figure 1. The stream has
formed a small valley in the landscape that continues The limestone in SW Skåne has undergone major
downstream (Kreuger et al. 1998). faulting. This has resulted in a valley known as Al-
narpsdalen. The valley has been filled with coarse
sediments forming a high conductivity aquifer. The
2.2 Geology
aquifer is divided into two main parts, one aquifer to
The oldest known bedrock in the southern part of
the NW and one aquifer to the SE (Fig. 2). The
Skåne is made up of gneiss, gneisses granites and am-
groundwater divide is located between Svedala and
phibolites. Their origin is uncertain and they are only
Skurup. The groundwater divide has a NE-SW direc-
visible at two locations, Romeleåsen (a horst located to
tion. Parts of SE aquifer pass through the north region
the NW of Skurup) and at Torpaklint (a small horst)
of the investigated catchment area. The sediments are
(Daniel 1992).
composed of a gravel and sand mixture with a thick-
Overlying the bedrock is a limestone formation,
ness of over 50 meters (Gustavsson et al. 2005).
which was formed during middle Cretaceous to the
The limestone directly under this aquifer has a
late Tertiary period. These sediments contain uncon-
lower conductivity compared to the limestone located
solidated sandstone with a varying content of lime-
to the NE and SW. The upper parts of the limestone to
stone and chalk. The limestone can in some parts reach
the NE and SW consist of chalk and are highly
a thickness of up to 1000 meters, preserved thanks to
cracked resulting in a high conductivity (Gustavsson et
the Tornquist fault zone going through the area. The
al. 2005).
Tornquist zone has a direction of NW-SE and had its
Overlying the Alnarpsdal sediment aquifer is
highest intensity during the Jurassic and Cretaceous
glaciofluvial sediments composed of sand and gravel.
periods (Daniel 1992). The area NE of the fault zone
These sediments constitute the upper aquifer in Fig 2.
consists of older sedimentary bedrock whereas the SW
The glaciofluvial sediments are overlain by coarse
consist of younger sedimentary bedrock. Due to the
6
Figure 1. Quartenary map over the investigated area. Copyright of the background map from the National Land Survey of Swe-
den, grant I2010/0047.
3 Methods
The methods used in this study are; mapping of exist-
ing wells, measurements of groundwater level in the
already existing wells, sediment sampling during
drilling and well establishment, grain size analysis
(sieving and hydrometer analyses), Hazen’s method,
Hvorslevs slugtest, Bouwer and Rice slugtest, perco-
lation tube test, water sample collection and water bal-
ance calculation.

3.1 Mapping of existing wells
The first thing that was performed in the area was a
mapping of the existing wells. This was done to get an
overview of the groundwater level, to construct a hy-
draulic gradient map over the area, and to generalize
the groundwater flow direction. Each well location
was measured with a GPS and the water level was
measured using a flat tape water level meter. All wells
in the area were not accessible due to gravel or con-
Figure 2. Map of the regional hydrogeology SW of Skurup. crete cover or lack of approval to enter the estates.
1 is the SE aquifer and 2 is the upper investigated aquifer The wells used are shown in Fig 3, and the measured
(Map taken from Gustavsson 1999). groundwater level and well location can be seen in
appendix A. Geological data received from the Swed-
clayey till and clayey sandy silty till constituting a ish well archive (SGU) was studied to get an overview
confining layer to the aquifer (Gustavsson et al. 2005). of the geology of the catchment area. The purpose of
this was to create two profiles through the catchment
7
Figure 3. A map showing the location of the wells used for the hydraulic gradient map, wells 1 – 3 are the newly drilled wells
within the PEGASUS project and wells 4 – 20 are the already existing wells. Copyright of the background map from the Na-
tional Land Survey of Sweden, grant I2010/0047.
area to complement the profile made from the drilled monitoring wells located with a depth of c. 27 m, and

wells described under 3.2. The location for these pro- 7 m and at location 3 is the larger well located with a
files can be seen in Fig 4. depth of 22 m and one monitoring well with a depth of
5.5 m.
3.2 Well drilling During the drilling, samples were collected
As a more thorough research, six (2”) monitoring every meter for the deeper monitoring wells and every
wells and one larger (158,3 mm Ø) well were drilled in ½ m for the large well and the shallower monitoring
close connection to a surface watersampling station wells. The samples were placed in pre-marked plastic
used for environmental monitoring. bags and transported to the coldroom (4°C) for storage
The larger well was drilled at site 3 shown in and then analysed in the laboratory.
Fig 4 with a DTH – down the hole drilling with ring
bit, (“robit casing system”). The monitoring wells 3.3 Grain size analysis
were driven down with a pneumatic hammer and had a
closed point. 3.3.1 Sieve analysis
A total of seven wells were drilled to different The samples collected from the drilling were dried in
depths at three different locations shown in Fig 3. At an oven at 105 °C for 24 hours. Once dried the sam-
location 1 are three monitoring wells located, with ples were divided for sieving and hydrometer analysis.
depths of 35 m, 18 m and 10,5 m, at location 2 are two The sample size is based on the grain size, 200 g for
8
part of drill site 3, for which 25 g were used. The sam-
ples were mixed with 100 ml sodium phosphate
(Na P O ) and 300 ml distilled water in a 1000 ml
4 2 7
cylinder. The cylinder was sealed with para-film and
placed in a rotating cradle for 15 minutes. Distilled
water was then added up to the 990 ml mark and the
content was mixed with an agitator for 1 minute. Dis-
tilled water was used to wash off any sediment on the
agitator and to fill the cylinder to the 1000 ml mark. A
hydrometer was placed in the cylinder and measure-
ments were taken after 30 seconds, 1, 2, 5, 10, 20, 50,
100, 200, 400 minutes and 24 hours from the start. The
procedure was restarted after 24 hours until the results
coincided with the previous results. The results were
then put in the excel file KORNSTOR.xls to calculate
the percentage variation for use in Hazen’s method.
The result can be seen in appendix B.

3.4 Hazen’s method
The grain size results from the sieving were used to
calculate the hydraulic conductivity from “Hazen’s
equation”. The equation is only usable on samples
with an effective grain size between 0,1 – 3 mm
(Fetter 2001).
From the grain size analysis the hydraulic con-
ductivity was calculated through Equation 1 (Hazen in
Koenig et al. 1911). The unit for Equation 1 is in feet
per day which will be recalculated into metres per sec-
ond.

Equation 1
V 8200d2s
Figure. 4. The location for the 3 profiles over the local area,
Copyright of the background map from the National Land
Survey of Sweden, grant I2010/0047. Where
. V = water velocity (feet/day)
finer sediments and 500 g for coarser sediments. A d2 = the effective grain size and
200 g sample was used for each sieving analyses due s = the hydraulic gradient
to the fact that all samples analysed, mainly contain
fine sediments. Each sample was then washed through 3.5 Slugtest
a 0,0063 mm mesh sieve to remove the finest grains
Hvorslev’s slugtest (Fetter 2001) is a hydraulic con-
and oven dried again at 105 °C for 24 hours. Once
ductivity test carried out in the field.
dried, the samples were weighted again, to measure
One to two litres of distilled water with added
the amount of sediments <0,0063 mm. The coarser
sodium chloride (NaCl) were poured into the well. A
part of the sample was then put in a sieving column,
flat tape water level meter was used to measure the
which was placed in a sieve shaker for 15 minutes.
change in the water table until the water level had
The amount of sediments for each fraction was
fallen to at least 37 % of the original level. Measure-
weighted. The results were put in the excel file
ments were taken in even intervals. The intervals used
KORNSTOR.xls to calculate the percentage variation
varied between the wells due to different hydraulic
for further analyses, the result can be seen in appendix
conductivities. The measurements were then added to
B.
Excel to calculate the time it took for the water to fall

to 37 % of the original water level. Hvorslev’s equa-
3.3.2 Hydrometer tion, Equation 2 (Fetter 2001), was used for all the
Hydrometer analysis was conducted on samples that, wells except for the shallow well at well location 1.
from a visual inspection, had a content of >10 % Because the filter did not completely penetrate the
grains smaller than 0,0063 mm. The sample size groundwater surface at the time of the test. Bouwer
ranged from 25 – 100 g depending on the content of and Rice slugtest, Equation 3 (Fetter 2001), had to be
grains smaller than 0,0063 mm. The amount of 100 g used for that particular well.
was used for all samples, except those from the deeper
9