Transcript Geography of Warter

ENAS
Ente Acque
della Sardegna
14th European Seminar on Geography of Water
Facing climate change and desertification. Water Management in Sardinia
Drought Watch System in Sardinia to Reduce Supply
Vulnerability and Improve Water Resources
Management During Periods of Drought
Roberto Silvano
(Director of Water Resources Management and Remote Control Service - ENAS)
Presented by: Andrea Virdis
Water Resources Management and Remote Control Service
ENAS, Ente Acque della Sardegna, Italy
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Water Resources management in Italy
The management of the water resources in Italy and in the other Countries of the European Union underwent
during the past years through significant changes
The EU Water Framework Directive (WFD) (2000/60/EC) is the major piece of European Union (EU) legislation having
environment at its core. The Directive provides for a legislative framework aiming to protect Community waters in
qualitative as well as in quantitative terms
What marks the Water Framework Directive out is that it defines the quality of surface waters in terms of ecology rather
than chemistry or water pollution
Main aim of Member States is to restore the good ecological status (chemical, biological, hydromorphological) of
ground and surface water in the framework of the river basin producing the River Basin Management Plan, in each
river basin district
According to the devolution principle of the WFD, the environmental protection and monitoring, which was before a matter
under the control of the Nation, fell on hands of the Regions by the mean of the Basin Authorities. These are Bodies
created with the purpose of implementing, within their territory of competence, the Directive Rules
In 2006, the Italian Government started up the process wanted by the WFD by promulgating the Legislative Decree
152/2006 titled “Environment Policies” (“Norme in Materia Ambientale”), which reformed the entire body of environmental
regulations in Italy
The Decree 152/2006 lists eight river basin districts in Italy. The districts are: Serchio, Padano, Eastern Alps, Northern
Apennines, Central Apennines, Southern Apennines, Sardinia, and Sicily.
After the approval of the Legislative Decree 152/2006, the Sardinian Regional Authority reviewed competences and duties
in the area of Water Resource, by means of the Regional Law 19/2006 “Rules on Water Resources and Hydrographic
Basins” “Disposizioni in materia di risorse idriche e bacini idrografici”
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Water Resources management in Sardinia
Regional Law 19/2006
The Regional law introduces the concept of “multi purpose water system”. This
system is created to deliver raw water to different categories of users,
contributing to keep a balance between supply’s quantity and costs
• In Sardinia, 80% of supplied water comes from artificial reservoirs (52 dams)
• Main uses of dams in Sardinia are for irrigation and drinking water
purposes
ITALY
58%
SARDINIA
37%
33%
25%
17%
6%
Hydroelectric
Irrigation
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Drinking water
10%
9%
4%
Industrial
2%
Other Uses
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Institutional Flowchart of Sardinian Water System
Regional Law
n.19/2006
Sardinian Regional Authority
Official assignment
Regional Basin Authority
Official assignment
Institutional Committee
River Basin District Agency
Managing Body of the multi purpose
water system: ENAS
Raw water supply
Abbanoa S.p.A.
Reclamation Consortia
ENAS is the Region’s
operational agency tasked
with managing the island’s
multi-purpose water system
It supplies the wholesale
water for the principal macro
demands of the region civil,
irrigational and industrial
Industrial Consortia
Integrated urban water
Authority (ATO)
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ENAS - Ente Acque della Sardegna
... since 1946 EAF
Regional Law n.19/2006
transformed EAF into ENAS
expanding and upgrading EAF by the
addition of major water works for
multi-purposes uses and the
experience and skills of staff coming
from the Land Reclamation Consortia
At the same time, ENAS gave in to
the Urban Water Service all the
waterworks for civil uses
Currently, the system comprises
works and infra-structure for the
collection, storage and conveyance
of raw water for multi-purposes sectors
•
•
•
•
•
34 dams (1.900 Mmc of storage capacity)
24 diversion dams,
850 km of aqueducts,
209 km of conveyance canals,
47 pumping plants (with 70 Megawatt of
installed power)
• 4 hydropower plants (13, 27.5, 1.3, 1.25
Megawatt)
to-day ENAS ...
ENAS – Distributed Volumes
CIVIL: to Abbanoa SpA, which is the Water Purification Company who is in charge of the Integrated
urban water management in Sardinia
IRRIGATIONAL: to the nine Land Reclamation Consortia who have the management, at retail level,
of raw water addressed to irriguous purposes
INDUSTRIAL: to five Industrial Consortia
Sector
In 2010 the following volumes were distributed
Yearly distribution (million of mc)
Water demand framework
Civil uses
221
1,5 million of inhabitant
Agricultural uses
327
160.000 equipped hectares
Industrial uses
27
11 industrial areas
TOTAL
575
Hydrological features and droughts in Sardinia
Sardinia is located in the
centre of the western basin
of the Mediterranean Sea
and has a surface area of
24.000 km² with a population
of 1.648.000 residents
The climate is prevalently
Mediterranean, characterized
by a long period of drought in
summer and mild and rainy
winters with isolated frosts
The amount of water resources available for civil, industrial and agricultural use
contracted critically in Sardinia about ten years ago due to hydrological
alterations which had occurred on the island over the last three decades,
similarly to the rest of the Mediterranean basin
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Mean water balance in Sardinia
Hydrological features and
droughts in Sardinia
Analysis of the historical hydrological series in Sardinia over the past 90 years shows that both the rainfall
and runoff are non-stationary in the mean
Annual runoff into the reservoirs of Medio Flumendosa
800
Hydrological inflows display higher
stochasticity and their behaviour is
difficult to predict
700
Runoff (million of m3)
600
500
400
300
200
100
Hydrologic year
Yearly Runoff
Mean 1922-1974
Moving Average 4 years
Mean 1975-2008
Moving Average 7 years
Mean 1986-2008
07-08
Mean
The rainfall-runoff transformation in Sardinia proves
that runoff is highly sensitive to any reduction in
rainfall:
20% reduction in rainfall may produce a decrease
of 40% in runoff and consequently in water
resources available for human use.
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02-03
97-98
92-93
87-88
82-83
77-78
72-73
67-68
62-63
57-58
52-53
47-48
42-43
37-38
32-33
27-28
22-23
0
Such variability, which is linked to the
change in climatic conditions and has
high repercussions on the volumes that
can be supplied by water systems, and
makes it necessary to manage
resources using reliable and prudential
operational rules
Mean water balance in Sardinia
1922-1975
1975-2005
Rainfall
Runoff
Runoff coefficient
Rainfall
Runoff
Runoff coefficient
775 mm
245 mm
0.32
620 mm
145 mm
0.23
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Drought Management System in Sardinia
In this type of context, the management of complex interconnected hydraulic systems,
mainly based on large reservoirs regulating the water resources over multiannual periods,
plays a strategic role
A proactive action to be taken against droughts before they occur rather than simply
reacting to them, must be the aim of the strategy
It is crucial to define criteria and operational rules to minimizing water supply deficits and
to guarantee the sustainable use of natural runoff on a multi-annual base
The Region of Sardinia has in place since several years a drought alert and risk analysis
system for the management of multi-purpose water supply systems, with the aim to
reduce the vulnerability of supply and increase its reliability and avoid crisis situations
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Hydrological and Operational Droughts
Hydrological droughts:
random natural phenomena, revealed by analysis of the historical
hydrological data series
Operational droughts:
lack of water supply available to users
Hydrological droughts are transformed into Operational droughts by a
transformation function that considers the physical and size
characteristics of the water work system and the operational rules
selected to manage such waterworks
Drought is a phenomenon composed of both random natural aspects and
important human component
It is therefore essential to build a model that accounts for all such aspects
and delivers effective decision support
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Drought indices
An indicator that takes into account these aspects is the amount of
water reserves held in the artificial reservoirs of the regional water
system
This parameter is influenced both by the characteristics of the
hydrological inflows in the time and by the operational rules chosen to
manage reservoirs and the main water conveyance lines
The built model accounts for all such aspects by implementing a
calculation method that measure the indicator at monthly intervals, so
to make decisions based on such measurements
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The model: Methodology
This model, which is based on stochastic analysis principles, has two
components:
- a model to generate synthetic series of the runoff of Sardinian rivers
which preserves: a) the basic statistics of the historical series in each relevant
section of rivers of the regional territory; b) the time correlation structure; c) the
spatial correlation structure; d) specific drought statistics (persistence, duration,
intensity);
- a simulation model for operating the water supply system using
mathematical models to accurately represent both the functional characteristics
of structural elements (reservoirs, pipes, open channels, pumping plant,
hydroelectric plants, etc.) and the natural phenomena impacting the system, for
instance evaporation from reservoirs and the operational rules adopted for
optimum management of the resource
Using these two fundamental tools, a variable indicator is generated at
monthly intervals for each reservoir or for two or more reservoirs forming a
single water scheme
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The model: Methodology
The output of the model is a state indicator which as an excellent key
factor to measure the condition of water storage in the artificial
reservoirs
It is named Storage Frequency Index: Index of the probability of not
exceeding stored volumes, for each month of the year, in a single
hydraulic system
It represents the indicator adopted for the drought management system
in the region of Sardinia
This indicator summarizes both:
- natural elements (rainfall reduction and, therefore, runoff which feeds artificial
water basins)
- anthropic elements (the demand for water from basins, the rules governing
management of water resource transfer in complex hydraulic systems)
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Application of the Drought Management System in Sardinia
Curve of Storage Frequency Index
for each month of the year, in a single hydraulic system
Example: In April the probability of not
exceeding a stored volume of 1100
Mmc in the system is 0.8
(low
probability, 20%, of exceeding)
Tirso-Flumendosa system
Example: In April the probability of not
exceeding a stored volume of 200 Mmc
in the system is between 0.1 and 0.2
(high probability, 80-90% of exceeding)
Water Storage (million m3)
1200
1000
0.9-1.0
0.8-0.9
800
0.7-0.8
0.6-0.7
600
0.5-0.6
400
0.4-0.5
0.3-0.4
200
0.2-0.3
0.1-0.2
0
O
N
D
G
F
M
A
M
G
L
A
S
0.0-0.1
Month
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Application of the Drought Management System in Sardinia
The value of the drought state indicator, at monthly scale, can be
determined by matching the curves of the storage frequency index with the
current water storage in each system
Example 1):
In April if the current stored volume is 200 Mmc
Tirso-Flumendosa system
Consequently it is evident a critical state of the
hydraulic system
Example 2):
In April if the current stored volume is 1000 Mmc
The Storage Frequency Index is 0.5- 0.6 (that
means that the model has forecast an low
probability of exceeding 1000 Mmc)
Consequently it is evident a non critical state of
the hydraulic system
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1200
Water Storage (million m3)
The Storage Frequency Index is 0.1- 0.2 (that
means that the model has forecast an high
probability of exceeding 200 Mmc)
1000
0.9-1.0
0.8-0.9
800
0.7-0.8
0.6-0.7
600
0.5-0.6
400
0.4-0.5
0.3-0.4
200
0.2-0.3
0.1-0.2
0
O
N
D
G
F
M
A
M
G
L
A
S
0.0-0.1
Month
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Application of the Drought Management System in Sardinia
The values of the indicator have been grouped into four bands which,
correspond to different state of the hydraulic system and consequently to
different sets of decisions to be made and already identified in the water
crisis management plan
These four bands represent the four rules defined to implement specific
actions for an effective short-term drought mitigation measure
Definition of alert pointers
Storage Frequency Index
Probability of not exceeding
0.50 - 1.00
0.30 - 0.50
0.15 - 0.30
0
- 0.15
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Crisis level
ORDINARY REGIME (normal)
VIGILANCE (pre-alert)
DANGER (alert)
EMERGENCY
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Alert pointers and drought mitigation actions
Ordinary regime: for stored volumes in excess of the value that has a 50% probability of
not exceeding;
Vigilance level: for stored volumes within the values having between 50% and 30%
probability of not exceeding; It is necessary to monitor climate parameters to rapidly
identify any further fluctuations which may reduce the mean resources available.
Concurrently, consumption should be reduced to an amount that creates only limited
discomfort for users
Danger level: for stored volumes between the values with non-exceeding probability of
30% to 15%. Water supply must be reduced to a substantial degree, in order to face the
possible persistence of the dry period, and the planned mitigation measures must be
implemented;
Emergency level: for stored volumes within 15% of the probability of not exceeding; This
level should never be reached, since water supply should be restricted once the danger
level is reached. However, should the emergency level be reached, this would mean that
the statistical parameters of the series are continuing to change and therefore supply must
be restricted further and the annual mean of water available for distribution must be
reassessed.
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Application of the Drought Management System in Sardinia
Series of the monthly drought indicator Storage Frequency Index
Monti Pranu
Tirso-Flumendosa System
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Application of the Drought Management System in Sardinia
Drought indicators of Sardinian Reservoir
June 2008
March 2010
Different
characteristics
of alert for the
various water
systems of the
island
More uniform
and with
indicators
that show a
general
situation of
normality
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Remarks
The application of this method to Sardinian water system, over about three
years, has given good results to identify crisis areas and enforce mitigation
measures
This method can be more finely tuned and perfected
As experience has shown, some aspects require particularly careful assessment
and monitoring:
 it is preferable to anticipate shortages if the costs are not a linear function of the shortage; therefore it is preferable
to have several years with a moderate shortage rather than a single year with a high shortage;
 measures to meet an anticipated shortage generate costs even though such shortage may not occur;
 the timescale of such costs may cover several months or even years: this is a tough decision to make;
 risk perception: it is not easy to measure. Different individuals and organizations have different perceptions:
conflict situations;
 it is essential to pursue a technically balanced solution and seek agreement among stakeholders.
The tool implemented, identifies and describes crisis areas and situations by
means of easy-to-read quantitative parameters that represents a highly effective
aid to public participation and stakeholder consultation processes
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Thank you very much for you kind attention
ENTE ACQUE DELLA SARDEGNA
Via Mameli, 88 - 09123 Cagliari
Tel +39 070 - 60 21.1
Fax +39 070 – 670758
Water Resources Planning and
Remote Control Service
(Servizio Programmazione e Telecontrollo)
Ing. Roberto Silvano (Director)
Ing. Andrea Virdis
[email protected]
[email protected]
http://www.enas.sardegna.it