How to distinguish water scarcity and drought in EU water policy?

August 26th, 2013

Guido Schmidt & Carlos Benítez-Sanz, Intecsa-Inarsa, Madrid

Water scarcity and drought are two interrelated but distinct concepts. Despite widespread recognition of the important differences between the two concepts, there is no scientific agreement about the precise definitions of the terms water scarcity and drought;1 and due to the very similar effects of both events, water managers, the public, and the media often use the terms in an indistinct manner. This lack of clarity hampers the implementation of policies and measures which can adequately deal with the drivers and pressures of the two phenomena.2,3 The definitions commonly used are also often too lengthy, have contradictions and overlaps, and do not properly explain the interrelationships between the two events (see Understanding water scarcity: Definitions and measurements).

A screening exercise of 123 River Basin Management Plans (RBMPs) showed that both water scarcity and droughts are recognised as relevant issues by RBMPs across the EU. However, the exercise also showed that the analysis of water quantity aspects in many RBMPs lacks adequate foundation; the quantity data used are often insufficient; and the concepts of water scarcity and drought are not clearly distinguished.4

In order to improve water management in the EU, the concepts of drought and water scarcity need to be clearly differentiated in the next RBMPs cycle (2015-2021) along with the Drivers, Pressures, Status, Impacts, and Responses for each type of event. This is particularly important for understanding the (different) causes of water scarcity and drought, determining appropriate policy measures, and assessing their effectiveness. This is because, in order to design adequate policy responses to these events, it is necessary to make a distinction between droughts and water scarcity based on their causes and the opportunities for action.

In order to facilitate this aim, a set of working definitions has been developed by the co-operative EU Common Implementation Strategy for the Water Framework Directive Implementation process2 based on a review of previously used definitions and descriptions of water scarcity and drought events.5 According to the resulting definitions the two concepts can be distinguished as follows:

Drought is a natural phenomenon. It is a temporary, negative, and severe deviation along a significant time period and over a large region from average precipitation values (a rainfall deficit), which might lead to meteorological, agricultural, hydrological, and socioeconomic drought, depending on its severity and duration.

Water scarcity is a man-made phenomenon. It is a recurrent imbalance that arises from an overuse of water resources, caused by consumption being significantly higher than the natural renewable availability. Water scarcity can be aggravated by water pollution (reducing the suitability for different water uses), and during drought episodes.

While the two concepts are distinct, the definitions demonstrate that they are also closely related, and if either droughts or water scarcity pass certain thresholds, they can significantly affect the environment (terrestrial and freshwater ecosystems, air, soils), the economy (agriculture and water uses), and society (public water supplies, welfare, recreational activities, cultural and aesthetic values).6,7

There are, therefore, a number of similarities and differences between drought and water scarcity, and the key elements needed to define and compare the two concepts are set out in the table below:

Key elements for the definition of water scarcity and drought

Aspect Drought Water scarcity Causes Natural, due to a reduction of precipitation over a certain time period. High temperatures, strong winds, low relative humidity, timing (onset, duration, and end) as well as characteristics of rain can increase the severity. Man-made, due to an overuse of water resources, caused by consumption becoming significantly higher than the natural renewable availability, or pollution (reducing suitability for water uses). Occurrence Drought is a normal, recurrent feature of all climates and can happen in all parts of Europe. Its occurrence can be related to large-scale changes in atmospheric circulation patterns. Due to the increase in water consumption, water scarcity is increasingly prevelant and recurrent across Europe. Duration Droughts are highly variable in their duration and can last from a few weeks to several years. Water scarcity is usually characterised by a permanent and continued degradation of water ecosystems and reduced water availability for other (economic) functions. Impacts The impacts of both are highly variable according to the occurrence, severity, and duration of the event as well as the sensitivity of the affected ecosystems, economy, and society. They are also influenced by the relative humidity of soils, capacity of storage for groundwater, and streamflow of surface waters. When occurring in already water scarce areas, droughts have the most severe effects. Spatial extent Regarding geographical extension, droughts and water scarcity can both happen at a local level or cover entire RBDs. Drought events are even reported across wide areas of the EU. Predictability Drought forecasting is currently based on statistical analysis of historical occurrences and numerical weather forecasts, with a timeframe from a few days up to several months (generating increasing uncertainty). Implementation is planned in the frame of European Drought Observatory. Water scarcity is predictable for the mid- and long-term in the frame of RBMPs if adequate information on water availability and consumption and trends has been compiled, and considering the uncertainty e.g. of climate change predictions. Interaction When droughts occurr in an area characterised by water scarcity, their impact will be more severe as they are more vulnerable. Heat waves can aggravate droughts and water scarcity situations. Water scarcity can also be an effect of overexploitation due to (concurrent) drought events, but this does not apply vice versa i.e. drought is not an effect of water scarcity. Environmental thresholds (Freshwater) ecosystems are often characterised by, and adapted to, recurrent natural variations in precipitation and streamflow. Nonetheless, exceptionally severe droughts or the combined impact of droughts with man-made overabstraction / water scarcity can result in irreversible changes to ecosystems. Water scarcity usually affects the ecological status of ecosystems with the extent depending on duration, relevance, and the sensitivity of the ecosystem (including functions and elements). Costs In general, little data is available about the precise costs of water scarcity or drought situations (for marketable sectors, like agriculture and energy). Where data is available, it should evaluate the combined effects of a drought and geographically overlapping water-scarce area. Pan-European Indicators The European Drought Observatory offers a combined drought indicator, based on the Standard Precipitation Index (SPI), soil moisture and the Fraction of Absorbed Photosynthetically Active Radiation (fAPAR). The Water Exploitation Index has been developed by the European Environmental Agency. A refinement to reflect consumption data and monthly/seasonal resolution is still in the testing phase (WEI+). Possible measures to prevent or mitigate effects Drought forecasting, risk prevention (e.g. insurance, climate change adaptation, increased flexibility of water usage, increased water efficiency, protection of vulnerable species and habitats, governance rules for different drought thresholds) and emergency actions (e.g. water supply). RBMPs, water management, metering and allocation, water demand management, increase water efficiency and reuse, protection of vulnerable species and habitats, pricing policies etc. DPSIR focus Responses focus on Impacts. Responses focus on Drivers, Pressures, and Impacts. Possible policy responses Development of Drought Management Plans (DMPs), water allocation systems, and water governance rules and regulations. Support for insurance systems. Financial support for emergency actions (e.g. Solidarity Funds). Reduction of pressures via sectoral policies (e.g. agriculture, energy, urban development) related to water usage (e.g. on water-usage planning, water allocation and pricing systems, control)

Taking into account these definitions and the differences and similarities between water scarcity and drought events,8,9 the recent EU water policy review “A Blueprint to safeguard Europe’s waters”, promotes action lines for both concepts over the next few years. Some of these measures include e.g. enforcing water pricing/cost-recovery obligations under the Water Framework Directive; including metering when relevant; completing the hydro-economic model for Europe and establishing water accounts; developing guidance on and implementing environmental flows; applying GMES services to detect illegal abstraction; and further developing the European Drought Observatory.10 By recognising the distinct and interrelated aspects of water scarcity and drought, the EU is attempting to improve water governance and implement water policies designed to tackle the particular issues of droughts or of water scarcity when appropriate.

References:

1. Mishra & Singh (2010): A review of drought concepts. Journal of Hydrology 391: 202-216

2. CIS Expert Group on Water Scarcity & Drought (2012): Working definitions of Water Scarcity and Drought. URL: https://circabc.europa.eu/sd/d/02a234f7-ac60-4f81-bd8d-a3a0973e77d1/55171-Drought-WS_Definitions_V4-27Abril2012.doc (after ECAS registration only)

3. Van Loon, A. F., and H. A. J. Van Lanen (2013): Making the distinction between water scarcity and drought using an observation-modeling framework, Water Resour. Res., 49, 1483-1502, doi:10.1002/wrcr.20147.

4. Schmidt, G. & C. Benítez-Sanz (2012): Topic report on: Assessment of Water Scarcity and Drought aspects in a selection of European Union River Basin Management Plans. Study by Intecsa-Inarsa for the European Commission (under contract “Support to the implementation of the Water Framework Directive (2000/60/EC)” (070307/2011/600310/SER/D.2)). URL: http://ec.europa.eu/environment/water/quantity/pdf/Assessment%20WSD.pdf.

5. MED Joint Process WFD/EUWI Water Scarcity Drafting Group (2006): Water Scarcity Management in the Context of WFD. URL: http://ec.europa.eu/environment/water/quantity/pdf/comm_droughts/8a_1.pdf.

6. Xerochore (2007). Background Document II (Deliverable 5.1.). Synthesis report on Management and Policy Options for Conference on Drought. URL: http://www.feem-project.net/xerochore/files/D5.1.pdf.

7. CONHAZ (2012): Costs of Natural Hazards – A Synthesis. www.conhaz.org (accessed on March 2012)

8. European Commission (2012a). Report on the Review of the European Water Scarcity and Droughts Policy (COM/2012/0672 final). URL: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:52012DC0672:EN:NOT.

9. European Environmental Agency (2012): Water resources in Europe in the context of vulnerability

EEA 2012 state of water assessment. EEA Report No 11/2012. URL: http://www.eea.europa.eu/publications/water-resources-and-vulnerability.

10. European Commission (2012b). A Blueprint to Safeguard Europe’s Water Resources (COM/2012/0673 final). URL: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:52012DC0673:EN:NOT.

11. EEA (2009): Water Resources across Europe-confronting water scarcity and drought. EEA Report No 2/2009. URL: http://www.eea.europa.eu/publications/water-resources-across-europe.

Guido Schmidt is Senior Programme and Project Manager aiming to better understand, prevent and/or solve water and environmental problems and conflicts; with a focus on water policy and planning in water-scarce areas. Carlos Benítez-Sanz is Agricultural Engineer with over 20 years experience. His activity in recent years has focused on water planning under the Water Framework Directive in Spain: Ebro, Andalusian Mediterranean Basin and the Basque Country. He is also involved in supporting works for the European Commission. Both have supported the work of the mentioned EU Expert Group. The article is based on deliverables of the EU Expert Group on Water Scarcity and Droughts of the Common Implementation Strategy for the Water Framework Directive, namely Working definitions of Water Scarcity and Drought (2012), and the authors supported the Group’s work as consultants.

The views expressed in this article belong to the individual authors and do not represent the views of the Global Water Forum, the UNESCO Chair in Water Economics and Transboundary Water Governance, UNESCO, the Australian National University, or any of the institutions to which the authors are associated. Please see the Global Water Forum terms and conditions here.