water scarcity and drought cancelliere

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Water scarcity and droughts

Antonino Cancelliere

Department of Civil and Environmental Engineering

University of Catania, Italy

[email protected]

www.dica.unict.it/users/acance

HYDROLOGY

The presentation of IPCC Reports on climatic change has given new voice to concerns on the priority to be assigned to the adaptations to climatic change for avoiding

dramatic water crises affecting a large part of the world population.

At European level (WSDEN, 2007) a distinction is generally accepted between:

Mainly due to the natural stochastic variability of

hydrological variables often worsened by inefficient

water management :

DROUGHT

Unbalance between available water resources and increased demands mainly due to: population increase • urbanization and tourism growth • irrigated agriculture enlargement

PERMANENT WATER SCARCITY PROBLEMS

TEMPORARY WATER SHORTAGES

Introduction

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WATER SHORTAGE

WATER STRESS DESERTIFICATION Anthropic

DROUGHT ARIDITY Natural

Temporary Permanent

Includes natural as well as man induced phenomena

Water scarcity

Water scarcity

•  Average per capita available water is often used as a water scarcity indicator

•  Commonly, 2000 m3/person/year is the threshold for water stress, 1000 for water scarcity

•  Many countries experience less than 500 m3/person year of available water

•  Such indicator can sometimes be misleading –  Renewable vs. non conventional waters –  Presence of irrigation –  Large spatial variability

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Water availability

(UNEP, 2002)

Thousand m3/yr per capita

Processes influencing water scarcity

Natural Man induced

Climatic Hydrological

• Low average rainfall

• High rainfall variability

• Droughts

• Long dry seasons

• High temperature

• High evaporation

• Low infiltration

• Low soil moisture

• Ephimeral streamflow regime

• Short time runoff events

• Flash floods

• High erosion and sedimentation

• Low groundwater recharge

Climate change

Water management

• Temperature rise

• Rainfall decrease

• Higher frequency of extreme events

• Increased flood risk

• Change in vegetation and land cover

• Increasing demands

• Inequity in water allocation

• Inappropriate irrigation practices

• Lack of wastewater treatment and reuse

• Land misuse

• Inadequate infrasctructures

• Inadequate management

(Adapted from Pereira et al., 2009)

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Causes of water scarcity

1. Fresh water on earth is just a small portion of the total water (~2.5%) and is distributed enevenly in time and space

2. Pro-capita availability of water is dramatically reducing due to : n  Population increase n  Pollution n  Changes in climate According to Unesco (1996):

17.000 m3/yr · pro-capita in 1950 7.500 m3/yr · pro-capita in 1995

(Italy 2900 m3/yr; Jordan 150 m3/yr; Malta 80 m3/yr)

3.  Over 20% of world population does not have access to drinking water of good quality and almost 50% does not have sanitary systems (developing countries)

4.  Water costs will increase since resources more easily exploitable have already been exploited and because of the need to treat more and more polluted waters.

5.  Overexploitation of surface water is causing severe damages to t h e f l u v i a l e c o s y s t e m s ; overexploitation of acquifiers reduces both quantity and quality of groundwater.


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6.  Many countries suffer from an inefficient and ineffective water resources management.

7.  Access to water is not fully recognized as an universal right of men.


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Trends in water resources management

Until a few decades ago: –  To increase available resources to supply

increasing demands (hydraulics engineering)

Paradigm shift: –  More emphasis on demand management and on a

more efficient and effective management of existing water supply systems

–  Protection of ecosystems equilibrium also to pursue social equity and heritage from one generation to another (sustainable development)

Strategic proposals to fight water scarcity

Ø Desalination (municipal supply) Ø  Increased costs Ø Difficult to apply for developing countries

Ø Wastewater reuse (irrigation supply) Ø Hygenic constraints and allocation of extra costs

Ø  Increased efficiency in irrigation Ø Water saving Ø Water harvesting Ø Deficit irrigation Ø Virtual water trade

Ø Many virtual water importers among water rich countries Ø Many countries tend to guarantee food self sufficiency

Ø Use of green vs. blue water

High technology

Low technology

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Virtual water content in beverages

(from Schreier, 2006)

Numbers are indicative and should be adjusted to local conditions

Drought definitions •  Complex phenomenon, difficult to define •  A comprehensive definition is difficult since it

depends on: –  the component of hydrological cycle under investigation –  the time scale –  the way by which the deviation from the considered “normal

condition” is measured –  the purpose of the analysis

•  In general a distinction must be made between: –  Meteorological drought –  Agricultural drought –  Hydrological drought –  Water resources drought (operational) drought

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Drought processes and definitions

Soil moisture deficit

Unsaturated soil storage


Surface waterstorage


Groundwaterstorage

Groundwaterstorage

Water supply systemsWater supply systems

Socio-economic systemsSocio-economic systems

Actions to increase water availability


Actions to reducewater demand


Actions to mitigatedrought impacts


Precipitation deficit


Surface flow deficit

Groundwater deficit

Water supply shortage

Economic, social, environmental impacts


Meteorological drought

Agriculturaldrought

Hydrologicaldrought

Water resourcedrought (operational)

Soil moisture deficit





Groundwaterstorage

Groundwaterstorage

Water supply systemsWater supply systems

Socio-economic systemsSocio-economic systems









Surface flow deficit

Groundwater deficit

Water supply shortage



Meteorological drought

Agriculturaldrought

Hydrologicaldrought

Water resourcedrought (operational)

Natural disasters

Floods31%

Storms33%

Droughts22%

Earthquakes10%

Others4%

Floods34%

Storms24%

Droughts35%

Earthquakes4%

Others3%

Damage

Affected people

Source: United Nations, 1994

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Drought analysis

•  Drought is caused by anomalies (deficits) of hydrological variables and/or water supply

•  Anomalies: negative deviations (or departures) from “normal” conditions

•  Drought indices attempts to measure and characterize in an objective and possibly standardized way such anomalies

Requisites of drought indices

•  To be representative of the type of drought of interest (meteorological, agricultural, hydrological, etc.)

•  To enable an assessment of the severity of an historical or ongoing drought

•  Easyness of interpretation by non-specialists

•  Standardization, to enable comparisons in time and space

•  To be expressed in probabilistic terms

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Standardized Precipitation Index • The index is based on the consideration that each component of water resources systems reacts to a deficit in precipitation over different time scales (McKee et al., 1993).

Ø  e.g. soil moisture is affected by precipitation anomalies in very short time;

Ø  while streamflow, stored volumes in reservoirs and groundwater are affected by deficit over a large time scale;

• The index is computed on cumulated values of precipitation over various time periods (k=3, 6, 9, 12, 24, 48 months). • First a probability distribution (generally a gamma function) is fitted to the frequency curve of cumulated precipitation over k months for each individual month (e.g. January, February, etc.) • Then the value of the standard normal variable corresponding to the computed probability for actual cumulated precipitation is adopted as SPI.

•  SPI Standardized precipitation index (McKee et al, 1993) widely used for drought monitoring purposes

•  Multiple time scales •  Allows for comparison of

droughts conditions among different times, sites

Standardized Precipitation Index SPI Z Class ΔP (%)

Z ≥ 2.00 Extremely wet 2.2 1.50 ≤ Z < 2.00 Very wet 4.4

1.00 ≤ Z < 1.50 Moderately wet

9.1

-1.00 ≤ Z < 1.00 Near normal 68.6

-1.50 ≤ Z < -1.00 Moderately dry 9.1

-2.00 ≤ Z < -1.50 Z<-2.00

Severely dry Extremely dry

4.4

2.2

d)distributenormally is ionprecipitat aggregated ifexact (

roughly

,, k

kkk YZ

τ

ττντν σ

µ−=

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SPI Index: k=12 months

ANALISI DELLA SICCITA' INDICE SPI k = 12

Stazione: Acireale Quota (m s.m.): 194Bacino idrografico: Precipitazione media annua (mm): 814Distretto idrografico: 7. EST-SETTENTRIONALE Periodo d'osservazione dal : gen-1921 al: dic-2000Versante: EST Periodo utile dei risultati dal: set-1924 al ago-2000

Mesi: 912

Bacini minori fra Simeto e Alcantara

-4

-3

-2

-1

0

1

2

3

4

set-1977 set-1981 set-1985 set-1989 set-1993 set-1997 set-2001

SPI

-4

-3

-2

-1

0

1

2

3

4


SPI

-4

-3

-2

-1

0

1

2

3

4

ago-1949 ago-1953 ago-1957 ago-1961 ago-1965 ago-1969 ago-1973 ago-1977

SPI

SPI Index: k=36 months ANALISI DELLA SICCITA' INDICE SPI k = 36

Stazione: Acireale Quota (m s.m.): 194Bacino idrografico: Precipitazione media annua (mm): 814Distretto idrografico: 7. EST-SETTENTRIONALE Periodo d'osservazione dal : gen-1921 al: dic-2000Versante: EST Periodo utile dei risultati dal: set-1924 al ago-2000

Mesi: 912

Bacini minori fra Simeto e Alcantara

-4

-3

-2

-1

0

1

2

3

4


SPI

-4

-3

-2

-1

0

1

2

3

4


SPI

-4

-3

-2

-1

0

1

2

3

4

ago-1949 ago-1953 ago-1957 ago-1961 ago-1965 ago-1969 ago-1973 ago-1977

SPI

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SPI index in Sicily: January 2002

SPI index in Sicily: January 2005

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Historical series of SPI for different k (Acireale station)

SPI series in 43 precipitation stations in Sicily (k=12 months)

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Piet Mondrian, Broadway Boogie Woogie, 1949

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Role of drought monitoring for mitigation

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Drought mitigation approach in ancient Greece

•  Should a drought persist for a long time, and the seeds in the earth and the trees wither, then the priest of Lycaean Zeus, after praying towards the water and making the usual sacrifices, lowers an oak branch to the surface of the spring, not letting it sink deep. Pausanias, Description of Greece: book 8, chapter 38, section 4 [Arcadia]

•  These asked for a cure for the drought, and were bidden by the Pythian priestess to go to Trophonius at Lebadeia and to discover the remedy from him. Pausanias, Description of Greece: book 9, chapter 40, section 1 [Boeotia]

Current reactive approach

Awareness

Panic (emergency)

Precipitation

Oblivion

Lack of precipitation

Drought

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Proactive approach for drought mitigation

Long-term measures Short-term measures

S u p p l y increase

- New storage facilities -  Water transfers and use exchange

-  Non-conventional resources (wastewater, desalination)

-  Use of marginal water sources

-  Relaxing environmental constraints

-  Improvement of efficiency

D e m a n d r e d u c t i o n , water saving

- Dual municipal distribution networks

- Water recycle in industries - Reduction of irrigation consumption (new crops and irrigation techniques)

-  Restriction on municipal uses

-  Restriction on annual crops

- Water saving campaigns - Mandatory rationing

I m p a c t minimisation

- Early warning system and drought contingency plan

- Quality-based reallocation of water resources

- Insurance and economic policies

-  Temporary reallocation of resources

-  Public aid and tax relief -  Rehabilitation programs

Drought mitigation measures

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Drought mitigation measures

Difficulties in planning a drought mitigation strategy (1/2)

•  Inadequate understanding of natural drought phenomenon

•  Low appreciation of a pro-active approach for

coping with natural hazards

•  Difficulty in quantifying the impacts of drought on different sectors (economy, environment, society)

•  Strong conflicts among different groups of

interest •  Legal and institutional constraints on the

implementation of drought mitigation measures

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Difficulties in planning a drought mitigation strategy (2/2)

•  Inadequate development of tools aimed to assess the identified measures and to support the decision-making process;

•  Lack of an early warning of water

deficiency based on monitoring of hydrometeorological variables and water availability

•  Lack of a consolidated (horizontal)

coordination among water management agencies and of (vertical) communication among different decision levels.

Conclusions •  Many countries in the world and in the Mediterranean basin

in particular suffer or will suffer in the future from water scarcity, due to increasing demands and reduced available water

•  Measures to cope with permanent water scarcity should be tailored to the particular region/country/watershed, since they have a strong impact on the local economy, social life, culture.

•  Droughts, despite being a natural feature of every climate, yet are one of the main causes of water scarcity

•  An effective mitigation of droughts is possible, provided an accurate monitoring and forecasting is in effect, and appropriate measures are planned in advance according to a pro-active approach

water scarcity and drought cancelliere

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