Ann Calver (WMO Commission for Hydrology Advisory Group Member leading on ‘Water, Climate & Risk Management’)

UK Drought Management and Monitoring

WMO/ISDR Expert Group Meeting on Hydrological Drought Indices

Geneva 1-2 September 2011

1

Drought in the UK

Source: UK Climate Change Adaptation Sub-Ccmmittee, 2011; Rodda & Marsh, 2011

uses of abstracted water

rainfall June-Aug 1976

as % of 1971-2000 mean

drought orders issued in England 1976-2008

2

River flow indicators

3Source: Environment Agency

RIVER THAMES AT KINGSTON (NATURAL)Forecasts of mean monthly river flow from July 2006 for 12 months for different % average rainfall

0

5000

10000

15000

20000

25000

30000

35000

Oct-04 Jan-05 Apr-05 Jul-05 Oct-05 Jan-06 Apr-06 Jul-06 Oct-06 Jan-07 Apr-07

Flow

(Ml/d

)

Excep High Note High Above norm Norm Below norm Note low Excep low Actual

120%

% of AverageRainfall

100%80%60%

Projecting river flow indicators

4Source: Environment Agency

Groundwater level indicators

5Source: Environment Agency

Reservoir stock indicators

6Source: Environment Agency

Soil water indicators

7Source: Environment Agency

Drought management plans

EU Environmental Regulator Water Utility

8Source: EU, Environment Agency, Anglian Water

Environmental regulator’s drought management plan

9Source: Environment Agency

Water utility drought manage-ment plan: potential droughtsituation

10Source: Anglian Water

Water utility drought manage-ment plan: during drought conditions

11Source: Anglian Water

Translation of hydrological and other information into determination of an ongoing drought situation

12Source: Environment Agency

European level drought indicator use (1)

hydrological indicator use water scarcity/availability indicator use

Similar EEA information on water scarcity and drought indicators is available relating to meteorological, agricultural, adaptation & mitigation, water abstraction, economic and environmental issues

13Source: European Environment Agency

European level drought indicator use (2)

Examples of existing indicators used by Member States to identify and manage droughts

‘ ... UK, Spain, Portugal, Finland, Italy, Netherlands and France have presented drought indicators ...’

‘ ... there are two main types of indicators, those that are used to prepare for an event and those which make it possible to characterise the event ... ‘

‘ ... all indicators require a complex combination of different parameters and numerous samplings and monitoring systems ...’

‘ .. there is a need for a good and complete indicator system to compare and define droughts ...’

‘ ... parameters included ... may vary from one country to another ... to integrate the specifics of different climatic and geographic conditions ...’

‘ ... it is often not possible to use the single ‘rainfall’ factor to identify and manage a drought ...’

14Source: European Commission

Drought indicators outside the event management period

England & Wales Aridity Index

0.5

1

1.5

2

2.5

3

3.5

1766

1776

1786

1796

1806

1816

1826

1836

1846

1856

1866

1876

1886

1896

1906

1916

1926

1936

1946

1956

1966

1976

1986

1996

1995

1976

19591921 1949

19111933

1893

1870

18681826

20031990long term England & Wales

aridity indexbased on summer (April-September) rainfall and temperature anomalies

River Thames basin hydrological indicators during a long drought 1889-1910periods below long term averages shaded in red

15

Source: Marsh, Cole & Wilby, 2007

Seasonal and longer outlooks (1)

UK Met Office seasonal precipitation outlook

UKCP 09 rainfall scenarios under

anthropogenic climate changes

generated river flows using output from range of climate models

generated river flow changes using a single climate model

16Source: UK Met Office, CEH Wallingford

surface water – increased sensitivityto environmental derogation

groundwater – potential for poorer yields

Seasonal and longer outlooks (2)

mapping of groundwater drought susceptibilityin chalk aquifer (white)red - highest susceptibility; yellow moderate

17Source: British Geological Survey

Some concluding remarks relating to the wider use of hydrological drought indices

• Compelling need for evaluation of a range of drought indices [& drought forecasting methods] for potential use beyond their original destination

• Fitness for purpose is the key concern, together with early availability: ‘standard’ hydrological indicators have advantages but may not override local issues of availability, applicability etc

• Future indices may show greater use of remotely-sensed data and model-generated data, augmenting ‘conventional’ observations

• Indices do not remove the need for sound judgement

further information: anncalver@lwrc.co.uk18