Lake management in Italy

Lakes & Reservoirs: Research and Management 2003 8: 41–59
Lake management in Italy: the implications of the
Water Framework Directive
G. Premazzi1*, A. Dalmiglio2, A. C. Cardoso1 and G. Chiaudani3
1
2
Institute for Environment and Sustainability, European Commission, Joint Research Centre, 21020, Ispra, Italy,
Agenzia Regionale per la Protezione dell’Ambiente della Lombardia, Regione Lombardia, 20100, Milan, Italy, and 3 Biology
Department, University of Milan, 20100, Milan, Italy
Abstract
This paper constitutes the first consideration of the implications of the lake management in Italy arising from the requirements
of the Water Framework Directive (WFD), in comparison to the provisions of existing national legislation. As a matter of fact,
the Italian decrees anticipated the principles of the WFD and have substantially modified the legislation in the field of water
in Italy. Important changes were introduced, both in the monitoring systems and in the classification methods for surface
waters. The environmental quality status will be determined not only by monitoring the aqueous matrix, but also the sediment
and the biota. The new WFD is the major piece of European Union (EU) legislation with environment at its core; it will guide
the efforts for attaining a sustainable aquatic environment in the years to come. In the WFD one can see elements from all
the different forces that guided the reform of EU water policy: environmental protection, deregulation and subsidiarity.
Moreover, elements of the economic instruments approach (introduction of the cost recovery principle), quantitative concerns (setting of minimum flow objectives for rivers and abstraction limits for ground waters) and the quest for integration
(river basin management with representation of all stakeholders) are all reflected in the WFD. The paper summarizes
the present condition of the most important lakes in the Italian lake district and also highlights the case of Lake Varese,
representing a unique case of lake management in Italy. Preliminary results show that there are very few examples dealing
with the elements thought appropriate to lake water assessment as required by the WFD. The application of the objectives
of the type specified is a largely unknown issue.
Key words
ecological water status, European Union Water Framework Directive, Italian water legislation,
lake management, subalpine lakes.
BASIC LEGAL FRAMEWORK FOR WATER
QUALITY PROTECTION IN ITALY
In Italy the regions are charged with water monitoring
activities and the central government is empowered with
supervision, coordination and regulation tasks. The basic
legal framework for water quality protection and monitoring
is established by:
1. Legislative decree number 152/99, which transposes
the European Union (EU) Directives 91/271/EEC and
91/676/EEC, and defines the main requirements for
water quality monitoring in inland waters, coastal waters,
estuaries and lagoons (Decreto Legislativo 1999).
*Corresponding author. Email: [email protected]
Accepted for publication 29 November 2002.
2. Legislative decree number 258/00 (Decreto Legislativo
2000), which concerns the protection of water from
pollution and integrates thoroughly some topics of the
legislative decree 152/99 (Decreto Legislativo 1999). For
the first time in Italy, the two decrees set environmental
and functional objectives for water bodies.
3. Law 183/89 (Repubblica Italiana 1989) which establishes
river basins as the unit where environmental protection
activities have to be designed and performed, and creates
river basin authorities.
4. Law 36/94 (Repubblica Italiana 1994a) which concerns
the reorganization of the public services that are charged
with water abstraction, water supply and distribution, and
waste water treatment.
5. Law 61/94(Repubblica Italiana 1994b) which relates to
the reorganization of environmental controls and the
42
G. Premazzi et al.
Table 1.
Classification of the lakes’ ecological status†
Parameters
Transparency (m)
Hypolimnetic oxygen (% saturation)
Chlorophyll (µg/L)
Total phosphorus (µg/L)
CLASS 1
CLASS 2
CLASS 3
CLASS 4
CLASS 5
(high)
(good)
(moderate)
(poor)
(bad)
>5
5
2
1.5
1
>80
80
60
40.0
20
<3
6
>10
25.0
>25
<10
25
50
100.0
>100
†
See Decreto Legislativo (1999).
Table 2.
The main chemical compounds monitored in surface
inland waters†
Inorganic
Organic
cadmium
aldrin
total chromium
dieldrin
mercury
endrin
nickel
isodrin
lead
DDT‡
copper
hexachlorobenzene
zinc
hexachlorocyclohexane
hexachlorobutadiene
trichlorobenzene
chloroform
perchloroethylene
pentachlorophenol
tetrachloromethane
trichloroethylene
1,2 dichloroethane
†
See Decreto Legislativo (1999); ‡DDT, 1, 1, 1 trichloro-2, 2 bis
(4-chlorophenyl) ethane.
National Agency for Environmental Protection and
Regional Agencies
A reorganization of the administrative system for river
management has recently taken place in Italy, partly as a
result of recognition of the growing importance of taking an
integrated approach to environmental management. River
basin authorities have been set up covering six basins of
national importance (the largest and most important one is
that of the Po River), as well as 15 regional and 17 interregional basins.
The responsibility for environmental protection and
monitoring has been largely devolved from the national
level to the regions, provided that the minimum requirements of the national legislation are satisfied. The design of
monitoring programmes is undertaken at the local level, on
a case-by-case basis. The range and extent of programmes
may vary but local monitoring can be divided into different
categories, such as trend detection and general quality
characterization, discharge (point and diffuse) impact assessment and post-pollution incidents.
Both of the decrees anticipated the principles of
the EU Water Framework Directive (WFD) (European
Communities 2000) and have substantially modified the
legislation in the field of water in Italy. Important changes
were introduced, both in the monitoring systems and in the
classification methods for surface waters. The environmental
quality status will be determined not only by monitoring the
aqueous matrix, but also the sediment and the biota, the
latter intended both as accumulator of harmful substances
and recorder/integrator of environmental pressures.
The new monitoring system consists of two steps: a
cognitive phase and a full operational phase. In the first
phase (two-year duration), general information should be
gathered regarding surface water bodies, in order to be
acquainted with the lake and its environmental conditions
(for example, pressures from the catchment). This evaluation will permit the establishment of a monitoring plan, and
thus, the definition of the minimum number of sampling
points (depending on the lake size), the identification of
the criteria for selection of the sampling location and the
sampling frequency.
All lakes with a surface area 0.5 km2 should be monitored. For lakes with a surface area <80 km2, the sampling
point coincides with that of the maximum depth of the water
body. However, by default, in the absence of bathymetric
maps, it could be located at the centre of the lake. For lakes
with a surface area >80 km2 or of irregular configuration (for
example, forming bays or arms), the sampling points are
fixed on a case-by-case basis. In each of the fixed sampling
stations, chosen with respect to the desired information and
in conformity to local conditions, at least three sampling
depths should be considered: 1 m from the lake surface, 1 m
above the lake bottom and a depth in the middle of the
water column. For shallow lakes (z max 5 m) the number
of samples within the water column are reduced to two
(surface and bottom). For lakes deserving particular protection and safeguarding, the sampling profile should be
much more detailed. As an example, the monitoring programme undertaken in the deepest Italian lake, Como,
Italy’s Water Framework Directive
43
intended as a strategic water body for the abstraction of
drinking water and of particular environmental value,
includes six different stations for a total of 62 sampling
depths; only the water column at the maximum depth
(410 m) is described by 12 sampling depths.
The operational phase indicates that monitoring
programmes could take place at a reduced frequency and
at a limited number of sampling stations for only basic
(mandatory) quality elements, if the surface water bodies
concerned reach good/high status and there is no evidence
that the impacts on the water bodies have changed.
As concerns the classification of the lake quality status,
the allocation of a lake to a certain environmental class will
be done by referring to the ecological and chemical status.
A series of relevant quality elements are used for the
definition of the ecological status of lakes: these are mainly
ascribable to eutrophication. They include the following
physicochemical and chemical elements:
• Transparency (minimum annual value)
• Hypolimnetic oxygen saturation (minimum annual value
during stratification)
• Chlorophyll a (maximum annual value)
• Total phosphorus (P), (maximum annual value)
The classification of the ecological status shall be represented by the worst of the values from the monitoring results
of the quality elements. The assignment to the appropriate
water status will be done using the following class boundary numerical scale (Table 1).
The chemical status is defined as that exceeding (or not)
the threshold limits for some micropollutants and hazardous
substances, defined on a catchment basis for a reference
water body. The list of the main chemical compounds to be
monitored in surface inland waters is shown in Table 2.
The limit values and quality objectives established under
the five daughters directives of Directive 76/464/EECdangerous substances (European Communities 1976)-will
consider emission limit values and environmental quality
standards, respectively, in the evaluation of the chemical
status for lakes. Arithmetic mean values are considered for
the classification.
Therefore, the environmental status of a surface inland
Table 3.
water body shall be determined by its ecological and chemical status, and classified accordingly to the five classes set
out in Table 3.
BASIC FEATURES OF THE WATER
FRAMEWORK DIRECTIVE
The new WFD is the major piece of EU legislation with
environment at its core and it will guide efforts for attaining
a sustainable aquatic environment in the years to come. The
WFD is based on a ‘framework philosophy’ in line with the
principle of subsidiarity. It sets only the objectives to be
fulfilled by member states (for example, good water
quality), and defines the organizational structure (river
basin authorities) and mechanisms (existing legislation
and further measures) to achieve them. As such, the WFD
best exemplifies the new approach in the EU environmental
policy, where environmental protection is married with subsidiarity through the division of objectives at a European
level and standards/measures at a national level.
The WFD will also replace many of the ‘first waves’ legislation such as the directive on surface water for drinking
waters abstraction (European Communities 1979a) and the
fish and shellfish water directives (European Communities
1979b). This satisfies the call for deregulation (simplification) of the existing legislative framework. On the other
end, the European Commission considered that the public
health standards (such as those of the drinking and bathing
directives) should not be affected (European Commission
1996).
In the WFD one can see elements from all the different
forces that guided the reform of EU water policy, that is,
environmental protection, deregulation and subsidiarity.
Moreover, elements of the economic instruments approach
(introduction of the cost recovery principle), quantitative
concerns (setting of minimum flow objectives for rivers and
abstraction limits for ground waters) and the quest for
integration (river basin management with representation of
all stakeholders) are all reflected in the WFD.
A number of new strategies will result from the implementation of the WFD. Specific issues that are important in
formulating a sectorial strategy include the following:
Classification of the environmental status of surface inland water bodies†
Ecological status
CLASS 1
CLASS 2
CLASS 3
CLASS 4
CLASS 5
Threshold value
HIGH
GOOD
MODERATE
POOR
BAD
> Threshold value
POOR
POOR
POOR
POOR
BAD
Micro-pollutants and hazardous
substances concentrations,
as per Table 2
†
See Decreto Legislativo (1999)
44
G. Premazzi et al.
Table 4.
Comparison between the provisions in the Italian legislation and in the Water Framework Directive regarding determination of the
lakes’ ecological status
Decreto Legislativo number 152 (5/1999)†, Decreto Legislativo number 258 (8/2000)‡
Goals
To prevent and limit pollution; to restore polluted water bodies; to enhance the status of all water bodies; to ensure adequate
protection of those intended for particular uses; to promote sustainable use of water resources, with priority for those water bodies
intended for abstraction of drinking water; to maintain the natural self-depuration capacity of water bodies
What to monitor
Natural lakes with surface area 0.5 km2
Artificial lakes with surface area 1 km2 or lake volume 5 106 m3
Sensitive lakes at altitude <1000 m (Urban Waste Water Treatment Directive) and surface area 0.3 km2
Quality indicators
Water:
Mandatory parameters: temperature, pH, transparency, conductivity, alkalinity, dissolved oxygen, hypolimnetic oxygen (% saturation),
chlorophyll a, total phoshorus, soluble reactive phosphorus, total nitrogen, nitrate, nitrites, ammonia
Additional parameters: 7 heavy metals, 15 organic micro-pollutants
Sediment:
Additional parameters: 8 heavy metals, polychlorinated biphenyls, polycylic aromatic hydrocarbons, TCCD,tetrachlorodibenzo-p-dioxin;
organochlorinated pesticides
Bioassays: on pore water and wet sediment using Daphnia magna, Selenastrum capricornutum, Chironomus tentans
Biota:
Bioassays: toxicity tests with Daphnia magna, mutagenetic and teratogenetic tests, algal tests, bioaccumulation of polychlorinated
biphenyls, DDT¶ and cadmium on autochthonous fish and macrobenthos
Sampling
Number of stations:
for lake surface <80 km2, 1 at maximum depth
for lake surface >80 km2 or of irregular configuration, 1 + n
Sampling depth:
lakes with zmax 5 m (2)
lakes with zmax 50 m (3)
lakes with zmax >50 m (5 + n)
lakes of particular environmental value (7 + n)
Frequency:
twice per year (winter circulation and summer stratification)
Classification of water status
Ecological status (trophic status): five classes from high to bad; allocation as the lowest value of the relevant quality elements
(transparency, hypolimnetic oxygen, chlorophyll a, total phosphorus)
Environmental status: a combination of the above ecological status with the chemical status, evaluated by the heavy metals and organic
micro-pollutants contents and the bioassays results. 5 classes from high to bad, if the micro-pollutants concentration is less than or
equal to threshold level. Two classes (poor and bad), if the micro-pollutants concentration is greater than threshold level
Directive 2000/60/EC of 22 December 2000§
Goals
To achieve sustainable management; to maintain the ecosystem’s functioning (including dependent wetlands and terrestrial ecosystems);
to reach good ecological status
What to monitor
lakes with a significant volume within a river basin district and significant trans-boundary lakes (surveillance monitoring)
lakes representative of the risk or overall impact of the pressures in the river basin district (operational monitoring)
lakes failing to achieve environmental objectives (investigative monitoring)
natural and artificial lakes with surface area 0.5 km2
Italy’s Water Framework Directive
45
River basin management
Combined approach
The new approach to water management requires water
to be managed on the basis of river basins, rather than
according to geographical or political boundaries. This
enables assessment of all activities which may affect the
watercourse, and their eventual control by measures which
may be specific to the conditions of the river basin. The WFD
requires river basin management plans to be drawn up on
a river basin basis. It may be necessary to subdivide a large
river basin into smaller units, and sometimes a particular
water type may justify its own plan.
Basically, two different approaches to tackle water pollution
exist at European (member state) level:
• limiting pollution at the source by setting emission limit
values (ELV) or other emission controls
• establishing water quality objectives (WQO) for water
bodies
The WFD is based on a combined approach where ELVs
and WQOs are used to mutually reinforce each other. In
any particular situation, the more rigorous approach will
apply. This combined approach is also in accordance with
principles established in the treaty (European Communities
1997). For example, the precautionary principle, which
suggests that environmental damage should, as a priority,
be rectified at the source and that environmental conditions
in the various regions shall be taken into consideration.
Programme of measures
Central to each river basin management plan is a programme
of measures to ensure that all waters in the river basin
achieve good water status. The starting point for this programme is the full implementation of any relevant national
or local legislation as well as of a range of EU legislation on
water and related issues. If this basic set of measures is not
enough to ensure that the goal of good water status is
reached, the programme must be supplemented with whatever further measures are necessary. These might include
stricter controls on polluting emissions from industry or
agriculture and urban waste water sources In this context,
land use planning might be a key issue to be taken into
account.
Table 4.
Monitoring programme
Monitoring is an essential part of the implementation of
the WFD. Such systematic monitoring of surface water
and groundwater quality and quantity can be categorized
as:
1. Surveillance monitoring, which is undertaken to provide
information on the status of water, to identify its initial condition and to assess long-term changes, both from natural
and anthropogenic activities, in the catchment basin.
(continued)
Quality indicators
Biological elements: composition, abundance and biomass of phytoplankton; composition and abundance of other aquatic flora and
benthic invertebrate fauna; composition, abundance and age structure of fish fauna
Hydromorphological elements: hydrological regime (quantity and dynamics of water flow, residence time connection to groundwater
body); morphological conditions (lake depth variation, quantity, structure and substrate of lake bed; structure of lake shore)
Chemical and physicochemical elements: general (transparency, thermal conditions, oxygenation conditions, salinity, acidification status,
nutrient conditions); specific pollutants (all priority substances discharged into the body of water, pollution by other substances identi
fied as being discharged in significant quantities into a water body)
Sampling
Frequency:
Surveillance monitoring: for each monitoring site; at least for one year if covered by a river basin management plan
Operational monitoring: frequency to be determined by member states, so as to provide sufficient data for reliable assessment of the
status of the relevant quality element. The table in Annex V, paragraph 1. 3. 4. gives some frequency guidelines. For example, the
physicochemical elements should be monitored every 3 months, with the exception of the priority substances (monthly); the
biological elements should be monitored every 3 years, with the exception of phytoplankton (every 6 months)
Classification of water status
Ecological status: five classes from high to bad (table in Annex V, paragraph 1. 4. 2.); the status of quality is identified as the lower of
the values for the biological and physicochemical monitoring results
Chemical status: two classes, good and failing to achieve good; good indicates compliance with all water quality standards as
established in Annex IX, article 16
†
See Decreto Legislativo (1999); ‡see Decreto Legislativo (2000); §see European Communities (2000).
¶
DDT, 1,1,1 trichloro-2,2 bis (4-chlorophenyl) ethane.
46
G. Premazzi et al.
Italy’s Water Framework Directive
2. Operational monitoring, which is undertaken to assess
the success, or otherwise, of measures enacted to
improve the situation.
3. Investigative monitoring, which is undertaken in problem
areas where an accidental pollution has occurred or
where the causes of a problem in meeting environmental
objectives is not known.
Data on monitoring is publicly available, and also forms
the basis for regular reporting to the European Commission,
as well as contributing to the monitoring network within the
European Environment Agency.
Cost recovery
The application of economic instruments such as charges
for use of water as a resource or for the discharge of
effluents into watercourses is a policy explicitly endorsed
in the new directive. The ‘polluter pays’ principle must be
applied, and economic assessment becomes an essential part
of water management planning. The principle of charges for
water reflecting true costs is a radical innovation at European
level. There is a danger in this proposal that water may
become too expensive a commodity for many, and a general
reduction in its beneficial use may result.
Public consultation
The WFD requires consultation to take place and the relevant authorities should arrange consultation mechanisms
with the interested parties such as the general public,
non-government organizations, farmers and water companies. In this context, consultation with all relevant
parties might achieve a best cost-effectiveness and identify
the best combination of measures on a proportionate
level. Therefore, preparation of those parts of the WFD
addressing information and consultation of all stakeholder
groups and the public, should be subject to serious
efforts.
Integration of stakeholders and the civil society in decision making, by promoting transparency and information
to the public and by offering a unique opportunity for
involving stakeholders in the development of river basin
management plans, is a central concept of the WFD.
Fig. 1.
Map of the Italian lake district (Passino et al. 1999). Area,
71 057 km2; Regions, Piemonte, Valle d’Aosta, Lombardia,
Veneto, Liguria, Emilia-Romagna, Provincia Autonoma di Trento;
Population, 16 000 000; head of cattle, 4 188 000; head of
pigs, 5 232 000; maximum population density (Lambro area),
1478 inhabitants (ab)/km2; minimum population density (Trebbia
valley), 25 (ab)/km2; groundwater abstractions, 5.3 109 m3/year;
surface water abstractions, 25.1 109 m3/year.
47
The comparison of the provisions, considered by the legislative decrees and the WFD, for the determination of the
ecological status of lakes, is reported in Table 4.
THE PRESENT CONDITION OF THE MOST
IMPORTANT LAKES IN THE ITALIAN
LAKE DISTRICT
In Italy there are more than 2000 lakes. Of these, 389 are
freshwater (natural, enlarged natural and reservoirs) and 104
are coastal with brackish water, excluding lagoons. One
hundred and forty seven of these aquatic environments
(87 lakes and 60 reservoirs) have been classified according
to Organization for Economic Cooperation and Development
criteria. P is the main substance responsible for the eutrophication process because it was identified as the limiting
factor in 85% of examined lakes. Only 19% of lakes and reservoirs are in oligotrophic conditions, 40% are classified as
mesotrophic and 41% as eutrophic. Among these, 10% are
considered to be hypertrophic (Ministry of the Environment
1997).
The most important Italian lake district is located in
northern Italy and includes the deep subalpine lakes and
some small-medium insubrian lakes (Fig. 1). Together
these represent more than 80% of the total Italian lacustrine
volume.
Hereinafter, it is intended to summarize the state-of-theart knowledge of the selected Italian subalpine lakes Como,
Garda, Iseo, Maggiore and Varese. In particular, focus has
been placed on those parameters directly linked to the lake
trophy (nutrients) and on some biological elements (phytoplankton, zooplankton and fish) in view of the implementation of Decreto Legislativo number 258/00 (Decreto
Legislativo 2000) and the WFD. The case study of Lake
Varese is highlighted because it represents a case of lake
management which is unique in Italy, in which lake restoration technology is applied to accelerate the return to
earlier (more natural) conditions, after being impacted by
eutrophication.
General characteristics
Table 5 summarizes the main morphometric and hydrologic
characteristics of the lakes Como, Garda, Iseo, Maggiore and
Varese. According to the Consiglio Nazionale delle Ricerche
Istituto di Ricerca sulle Acque (1984), Lake Como (or Lario)
is the deepest Italian lake and the third in terms of surface
area and volume, after lakes Garda (or Benaco) and
Maggiore (or Verbano). Its drainage basin occupies an area
of 4552 km2, of which 487 km2 is in the Swiss territory. The
particular shape of the lake forms three distinct sub-basins:
the western basin (Como), the eastern basin (Lecco) and
an upper basin.
48
G. Premazzi et al.
Lake Varese is a relatively small Insubrian lake, belonging to the catchment area of Lake, Maggiore. It has had a
long history (since the 1960s) of water quality deterioration
as the result of cultural eutrophication. Its catchment basin
is one of the most densely populated areas in Italy (up to
700 inhabitants/km2) and is associated with many industrial
and commercial activities. It is the first example in Italy of
the use of in-lake methods to counteract the problems
caused by excessive nutrient enrichment.
The rainfall regime has the typical behaviour of alpine
areas, with concentration of precipitation between May and
November. Approximately 70–75% of the mean annual
precipitation volume (1200 mm/year for Lake Garda,
1800 mm/year for Lake Maggiore) is concentrated in
this period.
Lake Garda (Benaco) is the largest Italian lake with a
surface area of 368 km2 and it is located 65 m a. s. l. (lower
altitude by comparing with the other Italian subalpine
lakes). Lake to drainage area ratio is about 1/6, lower in
respect to that of other lakes (≈ 1/30). Two sub-basins can
be distinguished.
Lake Iseo (or Sebino) is the fourth Italian lake with a
surface area of 60.9 km2. A specific feature is that it
includes the largest European lacustrine island (area,
4 km2; height, 414 m).
Lake Maggiore (Verbano) is the second Italian lake in
terms of surface area and volume. Its drainage basin
occupies an area of 6600 km2, of which 50% is in the
Swiss territory. Yet 80% of the lake surface is in Italian
territory.
Table 5.
Main morphometric and hydrological characteristics of the subalpine lakes Como, Garda, Iseo, Maggiore and Varese†
Parameters
Como
Garda
Iseo
Maggiore
Varese
Latitude N
4610
4540
4544
4547
4548
Longitude E (G)‡
0916
1041
1004
840
845
Drainage area (km )
4522
2260
1736
6599
111.50
Lake area (km2)
145
368
60.9
212
14.52
Lake volume (106 m3)
23 372
49 030
7569
37 500
153
Lake volume (106 m3)
(w. basin)§: 9435
45 766
–
–
–
2
6
3
¶
Lake volume (10 m )
(e. basin) : 3702
3264
–
–
–
Lake volume (106 m3)
(u. basin)††: 10 236
–
–
–
–
Theoretical renewal time (year)
4.5
26.6
4.1
4
1.90
(w. basin): 10.8–14.5
(w. basin): 29.6
–
–
–
Effective renewal time (year)
(e. basin): 3.7–6.5
(e. basin): 2.1
–
–
–
Effective renewal time (year)
(u. basin): 7.1–9.7
–
–
–
–
Effective renewal time (year)
(lake): 10.4–12.8
–
15–18
14.5
2.80
410
350
258
370
26
Mean depth (m)
161
133
122
177
10.70
Mean lake level (m a. s. l)
198
65
186
194
238
Outflow discharge (m3/s)
158 (18–918)
58.4 (10–200)
58.9 (15–446)
298 (100–500)
2.9 (1.2–4.8)
Effective renewal time (year)
Maximum depth (m)
†
See Rossi & Premazzi (1975); Rossi & Premazzi (1991); ‡G, Greenwich. §w, western; ¶e, eastern;
††
u, upper.
Fig. 2.
The evolution of the
average dissolved oxygen concentration
in
the
hypolimnetic
waters of lakes Como, Garda,
Maggiore
and
Iseo
(Regione
Lombardia–Commissione
Europea
1997;
Commissione
Internazionale per la Protezione
delle Acque Italo-Svizzere 2001). ,
Como; , Garda; , Maggiore; ,
Iseo.
Italy’s Water Framework Directive
Lake water characteristics:
temperature and oxygen
Two hydrodynamic characteristics are of most importance
in the deep subalpine lakes, the water renewal time and
the vertical mixing. The effective mean residence time was
evaluated in all subalpine lakes because this parameter is
included in eutrophication models and its consideration is
indispensable in lake restoration. For Lake Maggiore, the
mean water renewal time has been estimated to be 14.5 years
by Piontelli and Tonolli (1964). Other lake renewal times
were estimated by Rossi and Premazzi (1975), Chiaudani
et al. (1986), Rossi and Premazzi (1991) and Rossi (1991),
as reported in Table 5. The second important hydrodynamic
feature of these great lakes is their specific holo-oligomixis.
An analysis of the thermal profiles suggests that these
water bodies can be considered as oligomictic basins
with a winter circulation (January–March) and summer
stratification (June–October). However, a complete
homogenization of the waters is only found in the
shallower basins with average temperatures ranging
from 5.5°C to 6.8°C. The lake volume affected by mixing
varies from 40% to about 70% of the total volume. The
complete overturn can only occur in conjunction with
particularly cold and windy winters. The mixing depths in
these lakes ranged from a minimum of 50 m to a maximum
of 250 m. For example, in Lake Maggiore in the past
50 years, only four complete overturns (1956, 1963, 1970,
Fig. 3.
The evolution of the
average total phosphorus concentration during spring circulation in
the lakes Como, Garda, Maggiore
and Iseo (Regione Lombardia–
Commissione
Europea
1997;
Commissione Internazionale per la
Protezione
delle
Acque
Italo-
Svizzere 2001). , Como; ,
Garda; , Maggiore; , Iseo.
Fig. 4.
The evolution of the
average total mineral nitrogen
concentration during spring circulation in the lakes Como, Garda,
Maggiore
and
Iseo
(Regione
Lombardia–Commissione Europea
1997; Commissione Internazionale
per la Protezione delle Acque ItaloSvizzere 2001). , Como; ,
Garda; , Maggiore; , Iseo.
49
1999) have occurred. In Lake Iseo since 1981, no full circulation occurred and the volume affected by mixing is less
than 50% of the total lake volume. The deepest basin of
this lake would be considered at risk of meromixis, and
consequently, noticeable chemical differences exist between
the upper 80 m of the water column (mixolimnion) and
the deepest layers. Thus, two different values should be
necessary to describe the chemical conditions of the lake
(Premazzi et al. 1998).
The evolution of the average dissolved oxygen concentration in the hypolimnetic waters of the lakes Como, Garda,
Maggiore and Iseo is represented in Fig. 2. Dissolved
oxygen is roughly present between 6 mg and 9 mg O2/L.
Despite the partial overturn of the waters, anoxic conditions
were never observed in the bottom layers where oxygen
saturation values fluctuated from 20% to 60%. The exceptions
are Lake Iseo, where in the deepest basin (below 200 m)
anoxic conditions were registered, and Lake Varese, where
from June to October anoxic conditions are measured in
about 60% of the lake volume. In the epilimnion of all
these lakes, typical conditions of over-saturation (110–140%)
are observed during the summer months, when primary
production is the highest. The oxygenation conditions of
the lakes Iseo and Varese would be considered unsatisfactory and typical of highly productive, eutrophicated
environments (Ambrosetti et al. 1992; Mosello et al. 1997;
Premazzi et al. 1998; Premazzi 2002).
50
G. Premazzi et al.
Nutrients and chlorophyll
meters, causal elements, and one response parameter,
chlorophyll concentration (Cardoso et al. 2001). The evolution of the average concentration of total P and of the
average concentration of total mineral N in the lakes
Phosphorus and nitrogen (N) are the main culprits of cultural eutrophication in freshwaters. Thus, the deviations
from a trophic level can be assessed with these two para-
Table 6.
Chlorophyll a concentration, cell density and biomass of phytoplankton in the epilimnion of the lakes Como, Garda, Iseo, Maggiore
and Varese†
Parameters
Como
Garda
5.4
4.5
Iseo
Maggiore
Varese
Density (106/L)
Mean
6.0
–
5.4
Minimum
0.3
0.2
0.1
–
0.2
Maximum
18.0
13.0
30.0
–
21.0
544.0
519.0
1558.0
Biomass (mg/m3)
Mean
960
6654.0
Minimum
48.0
100.0
234.0
200
300.0
Maximum
2031.0
1500.0
6451.0
2800
36 000.0
45.0
46.0
38.0
76–80
30.0
Mean
5.4
4.0
7.4
2.9
12.0
Minimum
0.8
0.5
0.7
0.5
1.0
Maximum
11.0
12.0
28.6
5.6
61.0
Species number
Chlorophyll (mg/m3)
†
See Commissione Internazionale per la Protezione delle Acque Italo-Svizzere (2001); Premazzi (2002); Dalmiglio (unpubl. data).
Table 7.
Zooplankton density and composition in the 0–50 m layer of the lakes Como, Garda, Iseo and Maggiore†
Como
Garda
Iseo
Maggiore
mean
–
–
–
3.00
minimum
–
–
–
0.50
maximum
–
–
–
10.00
–
0.15
–
1.50
Minimum
0.9
0.01
–
0.40
Maximum
3.4
2.00
–
6.00
Species number
3.0
6.00
2
6.00
0.15
Density (individuals/m3 104)
Copepoda
Mean density (individuals/m3 104)
Cladocera
Mean density (individuals/m3 104)
–
0.30
–
Minimum
0.2
–
–
–
Maximum
2.6
0.70
–
0.30
Species number
5.0
3.00
5
8.00
1.00
Rotatoria
Mean density (individuals/m3 104)
–
0.80
–
Minimum
1.0
–
–
–
Maximum
5.3
3.60
–
5.00
Species number
Total species
†
17.0
21.00
8
33.00
25.0
30.00
15
47.00
See de Bernardi et al. (1989); Manca et al. (1992); Commissione Internazionale per la Protezione delle Acque Italo-Svizzere (2001); Dalmiglio
(unpubl. data).
Italy’s Water Framework Directive
51
Como, Garda, Maggiore and Iseo is represented in Figs 3
and 4, respectively.
All four lakes underwent an increase in total P concentrations during the 1960s and reached their highest values
at the beginning of the 1980s, with the exception of Lake
Garda, which showed minimal modifications in its environ-
Table 8.
mental conditions. In the following years, due to several
technical (waste water treatment, load diversion) and
administrative (P ban in detergent) measures adopted to
prevent the onset of eutrophic phenomena, a significant
decrease in P levels was registered. Since the beginning of
the 1990s, a gradual decrease in P levels has been observed
Fish communities’ composition in deep subalpine lakes†
Species
Como
Garda
Iseo
Maggiore
Alburnus alburnus alborella
√
√
√
√
Alosa fallax lacustris
√
√
√
√
Alosa fallax nilotica
–
–
√
–
Anguilla anguilla
–
√
√
√
Anguilla vulgaris
√
–
–
–
Barbus plebejus
√
√
–
√
Blennius fluviatilis
–
–
–
√
Carassius carassius
–
√
√
–
Chondrostoma soetta
√
–
–
√
Cyprinus carpio
√
√
√
√
Coregonus morpha hybrida
√
√
√
√
Coregonus phoxinus phoxinus
–
√
–
–
Coregonus sp.
–
√
–
√
Coregonus macrophthalmus
√
–
–
√
Cottus gobio
√
√
√
√
Esox lucius
√
√
√
√
–
Ictalurus melas
–
√
–
Lepomis gibbosus
√
√
√
–
Leuciscus cephalus
√
√
√
√
Lota lota
√
√
√
√
Lucioperca lucioperca
–
–
–
√
Micropterus salmoides
–
√
√
√
Onchorynchus mykiss
√
–
√
–
Padogobius martensii
√
–
–
√
Perca fluviatilis
√
√
√
√
Phoxinus phoxinus
√
√
–
√
Rutilius erythrophthalmus
√
√
√
–
Rutilus rubilio
–
–
–
√
Rutilus pigus
√
√
–
√
Salmo gairdneri
–
√
–
–
Salmo trutta carpio
–
√
–
–
Salmo trutta fario
–
√
√
–
Salmo trutta lacustris
√
√
√
√
Salvelinus alpinus
√
–
√
–
Salvelinus fontinalis
–
√
–
√
Scardinius erythrophthalmus
√
√
√
√
√
Telestessoufia muticellus
√
–
–
Tinca tinca
√
√
√
√
Total number
24
27
23
26
†
See de Bernardi et al. (1989); Commissione Internazionale per la Protezione delle Acque Italo-Svizzere (2001); Dalmiglio (unpubl. data).
52
G. Premazzi et al.
in Lake Maggiore; the present trophic state of the lake can
be viewed as oligotrophic. Lake Iseo, however, shows two
distinct trends in P concentrations: in the mixolimnion
(0–80 m layer) these have decreased to the present value of
about 25 µg/L, while below 100 m mean values register at
approximately 80–85 µg/L (Premazzi et al. 1998).
In all four lakes, mineral N concentrations have shown a
general tendency to increase, followed in recent years by a
less marked increase, or even stability. Nitrate concentration
increase would be related to an increase in N loading from
the lakes’ catchment basin, mainly due to atmospheric inputs
rather than agricultural, domestic and industrial sources.
Nitrate is the most important nitrogen compound in the
subalpine lakes (up to 90–95% of the total). The low nitrate
concentrations in lake Garda (relative to the concentrations
in the other lakes) can be explained by a lesser impact of
eutrophication on this lake. The slower water renewal time
would result in a longer response time (higher resilience)
of Lake Garda to an increased N load (Ambrosetti et al.
1992).
In Table 6 the most recent data on chlorophyll a concentration for the subalpine lakes Como, Garda, Iseo Maggiore
and Varese is shown.
Phytoplankton
There are no comparative studies for phytoplankton on
the lakes Como, Garda, Iseo, Maggiore and Varese.
However, the composition of the phytoplankton communities
would register marked similarities from one lake to another,
as regards density, biomass and species composition. A
number of species are ubiquitous in these lakes. These
are the blue-greens Oscillatoria rubescens, Coelosphaerium
kuetzingianum and Microcystis sp., the diatoms Fragilaria
crotonensis, Melosira islandica, Cyclotella sp. and Asterionella
formosa, the coniugatophytes Mougeotia sp. and Closterium
acutum, the cryptophytes Cryptomonas erosa, Rhodomonas
lacustris and R. minuta, the chlorophyte Coelastrum sp. and
the dinoflagellate Ceratium hirundinella (Ambrosetti et al.
1992; Manca et al. 1992; Commissione Internazionale per la
Protezione delle Acque Italo-Svizzere 2001; Dalmiglio
(unpubl. data); Premazzi 2002).
It can be concluded that during the 1990s there was a
general decrease in the P concentration in the deep Italian
subalpine lakes. This, in its turn, has determined a decline
of the phytoplankton biomass. Concurrently, there was an
increase in the number of species with consequent generation of biodiversity of the phytoplankton communities, with
substitution in the dominant species. However, no particular
trend in biomass and chlorophyll a was evident, indicating
a high resilience in the phytoplankton response to P loading reduction. However, the most important taxa of the
phytoplankton communities are still represented by the bluegreens and the diatoms, even if replaced by new species.
Table 6 summarizes the most recent data on phytoplankton
density and biomass.
Zooplankton
The zooplankton found in the deep Italian subalpine lakes
is typically represented by: Copepoda Eudiaptomus padanus,
Cyclops abyssorum, Mixodiaptomus laciniatus and Mesocyclops
leuckarti, Cladocera Diaphanosoma brachyurum, Daphnia
hyalina, Eubosmina coregoni and Diaphanosoma brachiurum,
and Rotatoria Keratella cochlearis and Kellicotia longispina
(Dalmiglio (unpubl. data); Manca et al. 1992; Commissione
Internazionale per la Protezione delle Acque Italo-Svizzere
2001).
As regards studies on zooplankton, Lake Maggiore is the
most studied environment since the last century. It was
used as a test site for the discussion of theories and specific
problems of a complex community such as that living in a
large lake. Different aspects of the composition, evolution
and dynamics of zooplankton are detailed in a comprehensive review (de Bernardi et al. 1989). This lake would
be classified as a ‘copepods lake’, because this group
represents the most stable component of the populations.
Cladocerans are becoming progressively less abundant
(from 10% to 2% in the last 10 years). These organisms would
represent an indicator of the lake’s productivity.
An important feature of the zooplankton in Lake Como is
the rise in the density of cladocerans, due to Eubosmina
coregoni and Diaphanosoma brachiurum, that at present
represent a relevant portion of the zooplankton populations
(Dalmiglio (unpubl. data); Chiaudani & Premazzi 1993).
As concerns Lake Garda the marked dominance of
copepods (22% of the total zooplankton population) in
respect to cladocerans (2%) represents a positive signal
for the trophic conditions. In fact, the increase in the
density of cladocerans with an increase in the trophic
level (eutrophication) is a well-consolidated fact for several
water bodies (Manca et al. 1992).
Because of a lack of data, it is not possible to delineate the
evolution of the zooplankton populations in the lakes
Iseo and Varese. Table 7 illustrates the most recent data on
zooplankton in the lakes Como, Garda, Iseo and Maggiore.
Fish
There is scarcely any published data on fish communities
for the subalpine Italian lakes. Therefore, information to individualize trends in the fish populations of these lakes in connection with their trophic evolutions, which occurred in past
decades, is fragmentary and insufficient. Perhaps, the most
detailed studies on fish are those existing for Lake Maggiore.
Italy’s Water Framework Directive
53
change in respect to the 1980s when the catch of Alosa was
the most important commercial catch. Three pelagic fish
species (Alosa, Coregonus and Alborella) represent, on
average, more than 60% of the total catches in the lake.
This is a common characteristic of the deep subalpine lakes
that have a reduced littoral zone and a prevailing pelagic
area.
However, for the other Italian subalpine lakes some general
considerations can be made, based on qualitative observations (Dalmiglio (unpubl. data); Commissione Internazionale per la Protezione delle Acque Italo-Svizzere 2001).
In Table 8 are listed the species recorded in the deep lakes
Como, Garda, Iseo and Maggiore.
The decrease in Lake Maggiore of the total fish catch,
from 809 t/year in 1982 to 180 t/year in 1995, has been
paralleled by marked changes of in-lake P concentration.
From the data on fish population for Lake Como, two
periods can be identified: the first from 1960 to the end of
the 1970s, in which Cyprinids reached the highest values;
the second (1980s) in which a progressive increase of
Coregonus and Alosa was obser ved. Presently, these
represent the major component of professional fishing. It is
observed that the presence of Salmo trutta and Salvelinus
alpinus is significantly decreased in recent years.
Since the 1990s, Lake Garda has registered a marked
increase in the catches of Coregonus. In fact, the catch for
this fish was around 20 t/year in 1990 while six years later
it reached values of 140 t/year. It represents a noticeable
Table 9.
DISCUSSION
In order to achieve the established environmental quality
objectives, considerable technical, administrative and economical efforts were made. In the last decade, several agreements among the Ministry of the Environment, the local
authorities (Lombardy region and Varese province) and the
European Commission were signed aiming to assess the
environmental benefits of planned restoration programmes.
Intensive research activities were carried out and projects
developed (Chiaudani & Premazzi 1990; Chiaudani &
Premazzi 1993; Premazzi et al. 1995; Premazzi et al. 1998).
The reductions in P input to the lakes, due to the implementation of measures mentioned above, have in several
Representative water quality parameters (mean values at the overturn) in the subalpine lakes Como, Garda, Iseo, Maggiore and
Varese, for ex-ante (1980s) and ex-post (1999–2000) restoration periods†
Parameters (µg/L)
Como
Garda
Iseo
Maggiore
Varese
Ex-ante
78.0
12.0
32.0
20.0
325.0
Ex-post
39.0
14.0
53.0
10.0
95.0
Ex-ante
60.0
5.0
18.0
15.0
258.0
Ex-post
30.0
6.0
51.0
7.0
63.0
Ex-ante
805.0
375.0
695.0
800.0
–
Ex-post
878.0
383.0
773.0
820.0
–
Ex-ante
790.0
353.0
675.0
795.0
230.0
Ex-post
858.0
391.0
754.0
810.0
377.0
Ex-ante
4.6
7.0
6.9
7.5
1.7
Ex-post
7.9
9.0
5.5
15.0
3.5
Ex-ante
6.9
3.9
6.2
5.0
35.0
Ex-post
4.1
3.0
7.1
2.9
12.0
Natural phosphorus level
7.5
8.4
9.1
6.9
18.5
Final goal
9.4
10.5
11.4
8.6
23.0
Intermediate goal
14.1
15.7
13.5
10.3
35.0
Current phosphorus level
35.0
14.0
50.0
9.0
95.0
Total phosphorus
Reactive phosphorus
Mineral nitrogen
Nitrates
Transparency
Chlorophyll a
†
See Chiaudani & Premazzi (1993); Premazzi et al. (1998); Dalmiglio et al. (1999); Passino (1999); Commissione Internazionale per la
Protezione delle Acque Italo-Svizzere (2001); Premazzi (2002).
54
G. Premazzi et al.
cases reduced the in-lake P concentration and, in turn,
resulted in favourable shifts in the phytoplankton communities and in the chlorophyll a concentrations in the
majority of the subalpine lakes. Table 9 summarizes the lake
water quality before and after restoration programmes in the
lakes Como, Garda, Iseo, Maggiore and Varese. Figure 5
shows the present trophic level of these lakes with respect
to the natural background P level and the established water
quality objectives.
In addition to the emission limit value approach, the
regional authorities introduced the concept of receptive
capacity of the water body in their Water Clean-up Plans. It
gives the possibility of fixing stringent limits, according to
the natural lake characteristics and to the characteristics of
the contaminants (Piano Regionale Risanamento delle Acque
1992). This policy anticipated, in fact, the ‘combined
approach’ of the EU (that is, the integration of quality
objectives for water with emission standards for water
contaminants), as indicated in the WFD.
The Po River Authority has recently formulated directives
intending to safeguard lake water quality by counteracting
eutrophication of inland waters and taking into consideration
the lakes’ uses. Objectives to be pursued and strategies to
be adopted have also been defined (Autorità di Bacino del
Fiume Po (unpubl. data-internal document, 1998); Autorità
di Bacino del Fiume Po (unpubl. data-internal document,
2001)).
The trophic level cannot, however, be ignored in the definition of quality objectives. Although not ignoring water
quality criteria for different uses, a classification of qualitative
characteristics of lakes, referring mainly to the trophic level,
has been set up. The evaluation of present trophic levels,
such as oligotrophy, mesotrophy and eutrophy, is necessary
but not sufficient. Eutrophication is not necessarily the
Fig. 5.
Present conditions, water
quality objectives and natural background concentration of subalpine
lakes Como, Garda, Iseo, Maggiore
and Varese, expressed as total
phosphorus
concentration.
natural concentration;
, intermediate goal;
,
, final goal;
, current
concentration (Dalmiglio et al.
1999).
Table 10.
Comparison of the external phosphorus loading and the in-lake phosphorus level, and of the managerial and the ecological
objectives for the subalpine lakes Como, Garda, Iseo, Maggiore and Varese. The time required to attain the final goals of Water Clean-up
Programmes (ecological objectives) is also indicated†
Parameters
Como
Garda
Iseo
Maggiore
Varese
Phosphorus load (t/ year)
379.0
172.0
103.0
230–240
16
In-lake phosphorus level (µg/L)
35.0
15.0
24.0‡
9–10
95
Present condition
Managerial objective
Compatible phosphorus load (t/ year)
250.0
120–125
72.0
220–240
13–14
In-lake phosphorus level (µg/L)
16.0
10.5–11.5
16–18
9–10
35–40
144.0
119.0
65.0
200–212
10–11
Ecological objective
Phosphorus load (t/ year)
In-lake phosphorus level (µg/L)
Time required (year)
9.4
10.5
11.5
8
25–30
15–20
5–10
5–10
0
10–15
†
See Chiaudani & Premazzi (1990); Premazzi et al. (1995); Premazzi et al. (1998); Regione Lombardia–Commissione Europea (1997).
‡
average value in the mixoliminion. The annual average value for the lake is 56 mg/m3.
Italy’s Water Framework Directive
consequence of anthropogenic activities. Many lakes can
be naturally eutrophic due to their morphometric and
geochemical characteristics of the catchment basin. Thus,
the maximum objective achievable by restoration measures
should not necessarily be oligotrophy, but to bring each lake
to a level as close as possible to its presumptive natural
status. Hence, realistic management plans should establish
an ‘as close an approximation to a natural P state’ as the
maximum achievable water quality objective (ecological
objective) as possible, and an intermediate minimum water
quality objective (managerial objective), to be intended as a
P level in lake water which is acceptable for the social use
of the water resource (Chiaudani & Premazzi 1988)
Environmental quality objectives have been established
after evaluating the natural P levels for each lacustrine
environment in the Po river basin. The final ecological objectives were quantified as an increase of 20% in the natural P
concentration for oligotrophic and oligo-mesotrophic waters,
a 40% increase in the P level for mesotrophic and mesoeutrophic lakes and 50% for eutrophic lakes. Intermediate
managerial objectives were identified as a 40% increase in
the natural P concentration for oligo-mesotrophic lakes and
an 80% increase in the P level for eutrophic waters (Passino
et al. 1999). Table 10 compares the present situation of the
subalpine lakes with the above objectives.
The data from Dalmiglio et al. (1999) show a relative
improvement in the condition of lakes Como and Varese,
whereas Lake Iseo seems to have deteriorated in the last
10 years. The condition of Lake Garda is quite stable, indicating the high resilience of the largest Italian lake. In Lake
Maggiore the ecological objectives have been achieved.
The results of this research, coupling the combined
approach to the environmental benefit assessment, should
contribute to the improvement of water policy, making it
more effective in restoring and safeguarding the lake
environments.
Case study: Lake Varese
Lake Varese was first impacted by raw sewage (domestic and
industrial) from Varese agglomeration early in the 1960s.
Deteriorating water quality from algal blooms was reported
in the press (Editor, 1963; Giuliani, 1997)and the scientific
community addressed related issues (Vollenweider 1965).
By 1965, public concern had resulted in initiatives to
form a local agency (Consorzio Volontario di Tutela e
Risanamento delle Acque) to address the problem of the
lake’s management. The project, promoted by the action of
the Varese province in 1967, included (i) a sewerage network
(ii) an O-ring sewage diversion system, and (iii) a centralized wastewater treatment plant with phosphorus and nitrogen control. Waste waters received tertiary treatment in 1986
55
and diversion was completed in 1994 (de Fraja Frangipane
(unpubl. data-internal document, 1977); Premazzi (unpubl.
data-internal document, 1994)).
By the 1990s, Lake Varese was the subject of a cooperative research programme among the European Commission,
the Italian Ministry of the Environment, the Lombardy
region and the Varese province (Premazzi et al. 1995). The
goals of these studies were to evaluate the trophic status
and its temporal evolution and to assess the environmental
benefits of restoration programmes carried out in relation
to the established water quality objectives.
The water quality objective established by the Regional
Clean-up Act (Piano Regionale di Risanamento delle
Acque 1992) is to achieve a P concentration as close as
possible to the natural background P level with an intermediate objective of 40 µg/L and a final objective of
30 µg/L.
The lake responded in a relatively rapid way to decreased
nutrient loadings, as scientists had predicted. A marked
reduction of the external P loads was observed, from
50 t/year in the prediversion period in 1986 to 25 t/year in
1990, and to 11 t/year in 1997, as a result of the completion
of the depurative measures. The residual P load represents
no more than 18% of the total P load generated in the catchment basin: 75% is of diffuse origin.
By 1999, noticeable differences occurred. Total P
decreased from 290 µg/L to 120 µg/l, Secchi disc transparency increased from 1.8 m to 3.2 m and epilimnetic
chlorophyll decreased from 27 µg/L to 12 µg/L. Nitrogen
was no longer limiting after restoration efforts. It had
become a limiting nutrient because of the large biomass of
algae produced by increased P loads. Nuisance blooms of
algae were no longer a threat to the lake as in the previous
periods (Premazzi 2002).
However, mathematical models predicted quite a long
time (25–30 years) to attain the best P concentration at the
equilibrium (40–45 µg/L), even higher than that considered
to be the final restoration objective for the lake. These
models recognized the importance of internal P loading in
maintaining biological productivity of the lake (Rossi &
Premazzi 1991). Diversion of cultural nutrient loading,
although essential, may not be sufficient to return the lake,
suffering significant internal loads, to its undisturbed condition. Curtailment of internal loading may be also required.
Lake scientists predicted that the application of the in-lake
measure such as hypolimnetic withdrawal would accelerate
lake recovery by controlling P release from anoxic sediments (Premazzi 1994).
By the summer of 2000, siphoning the nutrient-rich deep
waters from the lake was effective because scientists convinced the authorities and the public that Lake Varese would
56
G. Premazzi et al.
become better in a shorter time than predicted from
loading models. In fact, scenarios for improving the lake
water quality would suggest a reduction of the total P concentration in the lake water up to approximately 25–30 µg/L
after a few water overturns (10–15 years). This calculated
equilibrium concentration is to be considered the closest
value, realistically attainable, to the natural background level
(20 µg/L). Preliminary results are greatly encouraging:
it appears that the greater the amount of phosphorus
discharged in this way, the greater is the decline in P
concentration in the upper water layers where algae
grow (Premazzi, unpubl. data).
FINAL CONCLUSIONS
Ideally, the knowledge about the water status of lakes
would derive from monitoring and classification as set
out in legislation, of which the Italian decrees are a good
example, and even from more comprehensive information
as required in the WFD. The WFD obliges member states
to provide information on the status of their lakes and to
assess long-term changes brought about by natural and
anthropogenic activities through a number of monitoring
obligations (surveillance monitoring). The Directive also
requires member states to set quality objectives for both
Table 11.
natural and artificial lakes. The status of lakes is assessed
through the observation of a number of elements that
include biological elements, hydro-morphological parameters and the physicochemical condition of the water
(Table 11).
In order to assess whether a lake falls within the appropriate category of ‘water status’, member states will have to
carry out sufficient monitoring of all these characteristics
as a minimum requirement. The acquired data is then used
to place the water body in one of the three quality classes,
high, good, or moderate, as defined in Annex V of the WFD
(European Communities 2000). ‘Good status’ is generally
described as a situation where the values of the biological
elements for a lake type show evidence of the impact of
human activity but deviate only slightly from those normally
associated with the lake type under undisturbed conditions.
Thus, the results of the monitoring systems will be
expressed as the ratio between the observed biological
parameters in a lake and the expected numerical value
for the pristine reference condition for that type of lake
(ecological quality ratio, EQR).
Conscious of the lack of experience in the use of many
biological elements for classification purposes as specified
in Annex V of the WFD, the European Commission
Quality elements to be considered in determining the water status for lakes†
Biological
Hydro-morphological
Chemical and physicochemical
Phytoplankton
Water flow regime
Transparency
Other aquatic flora
Connection with aquifers
Thermal conditions
Benthic invertebrates
Residence time
Oxygen levels
Fish
Lake shore
Salinity
Lake depth
Acidification status
Lake bed conditions
Nutrients
Specific pollutants
†
See European Communities (2000).
Table 12.
Examples of diverse compatibility by the European Union member states with the Water Framework Directive requirements for
monitoring nutrients
Member state
Monitoring of nutrients
Classification based on reference conditions
All lakes included
Belgium
No
–
–
Finland
Yes
No
Yes
Greece
No
–
–
Italy
Yes
Yes
>0.5 km2
UK (Scotland)
Yes
Yes
>1 km2
Sweden
Yes
Yes
Yes
Data elaborated by the Institute for Environment and Sustainability, Joint Research Centre, Ispra, from the questionnaire of Working Group
2.3, Reference Conditions, in European Commission (2002).
Italy’s Water Framework Directive
(Directorate, General Environment) set up in 2001 a working group on intercalibration (led by the Joint Research
Centre, Ispra). It aims at obtaining common understanding
of ecological status of the surface waters all over the EU and
at ensuring comparability of the EQR scales (that is,
good ecological quality should have the same ecological
meaning throughout the EU). Establishing comparable
class boundaries for four categories of natural waters is
crucial in order to have an equal level of ambition in
achieving ‘good status’ of the surface waters in different
member states. The intercalibration exercise, developed
within the Common Implementation Strategy of the WFD,
should be completed by June 2006 and results published by
December 2006.
However, the reality between the member states’
knowledge of their lakes’ quality status and the national
monitoring and classification systems is very different.
The above overview for the Italian subalpine lakes, resulting from a collation of information from several sources,
including the national monitoring programmes, gives us
an idea of the shortage of data, especially for biological
elements, in comparison to the requirements of the WFD.
These lakes are amongst the most surveyed in Italy, but
despite that, we would conclude that the current monitoring and classification system does not comply, on the whole,
with the WFD.
Yet, the situation in the rest of the EU is no better than
in Italy. Preliminary results from a questionnaire by the
REFCOND Project (European Commission 2002) show
that, even for the simplest quality elements (nutrients), there
are only three member states for which monitoring of
these in existing national classification systems is
compatible with the WFD requirements (Table 12).
The table shows that Italy and Sweden are two of the complying member states regarding the monitoring of nutrient
concentrations in lakes with more than 0.5 km2 surface area
and the classification of these considering its deviation
from reference (natural) nutrient values (National Board of
Waters and the Environment 1988; Wiederholm 1989;
Swedish Environmental Protection Agency 1991; Andersen
et al. 1997; Brunel et al., unpubl.data-internal report, 1997;
Vouristo 1998; Passino et al. 1999; Agence de l’eau 2000a;
Agence de l’eau 2000b).
The Scottish approach to lake classification identifies
four classes of water quality and establishes standards for
each of the classes. The water quality change associated with
nutrient enrichment is determined by the ratio of current
and hindcasted total P concentration.
Finland partially complies with the WFD because it
monitors nutrients on the basis of water uses, but does not
classify by comparing with reference conditions.
57
Belgium indicates that nutrients are not in the country’s
national monitoring programmes.
Greece reports that the national research infrastructure
is currently inadequate to meet the principal obligations that
the WFD places on the country.
Most of the existing experience of lake management
refers to the problem of eutrophication, as recently reviewed
by Cardoso et al. (2001). There are numerous data sets
available for specific lakes as a result of long-term studies
carried out by research organizations and universities to
assess trend evolution in the trophic state of lakes. In
practice, the data as required by the WFD is scarce and the
application of the new concept of ‘ecological status’ is a
largely unknown issue. This is a new concept to water
quality/quantity management and arises from consideration
that natural environmental conditions vary throughout the
EU. This must be taken into account in any water’s planning
project.
Management plans for lakes need to be refocused
because these surface bodies are often seen as a quite
separate issue in river basin management. The WFD
changes this attitude in that lakes must be considered as
ecological entities to be accounted for in any river basin
plans.
The need to reformulate the national monitoring networks
(and the classification systems) to include all the elements
that the WFD oblige member states to monitor, looks set to
be a must for all EU countries. On the other hand, there is
not much time left to do it: surveys should be completed by
2004 and in 2006 the monitoring programmes should start.
Before these dates, member states will have to design their
monitoring programmes and enact monitoring network(s)
able to carry out the sampling of all the elements in the WFD
with the appropriate density and frequency. These are major
tasks for such a short time available, and hopefully, there
will be progress from the current situation, where the
requirements of the WFD are still an ideal, to reality in due
time.
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