Systematic drought risk management using early warning indicators: Lessons from Kosovo
Brian L. Faulkner, www.waterconsultant.com, United Kingdom
The anticipated shut-down of the water supply system of the city of Cape Town, South Africa (“Day Zero”, May 2018), brought to international attention the fact that catastrophic failure of urban water supply can be dramatic without a well-defined and very rigorously enforced Drought Risk Management Plan (DRMP). Many frustrated residents have accused the city of mismanaging their water supply, and a parliamentary inquiry has now been ordered to this effect.1 Equally, requests for voluntary reductions in consumption appear to have gone largely unheeded by those same residents.2
Worldwide, urban population growth and climate change are increasingly leading to conditions of water scarcity in major agglomerations, where the balance between water use and water available is not being correctly managed. It is imperative that national water management agencies grasp this issue, and design and implement highly structured, publicly endorsed, and legally enforceable DRMPs. Progressively onerous restrictions at various phases of a DRMP can and should be based on relatively simple early warning systems derived from meteorological and hydrological indicators.
Significant droughts of six to 12 months duration (2006-07, 2012-13) were encountered in Prishtina (pop. 200,000+), Kosovo, a city increasingly vulnerable to droughts with limited water resources and storage, a rapidly increasing urban population and very high potable water losses. 3 Adaptation lessons from the 2006-07 drought were largely ignored by politicians and households. This was due to the fact that in October-November 2007, extreme rainfall rapidly refilled the main reservoirs; consequently general complacency set in about the imminent likelihood of a repeat drought.
The unpopularity generated by perceived ‘unnecessary’ water cuts if a rigorous, precautionary DRMP was to be followed also proved politically unpalatable. However, the repeat scenario of 2012-2013 led the German international development agency GIZ to fund a comprehensive study of Kosovo drought risk and management, with a particular emphasis on designing a practical and robust drought management framework for use by local water supply companies.4 Taking into account the generally ill-informed perceptions about drought hazard and consequence among politicians and households, it was felt that the only effective approach was a firmly ‘technocratic’ solution which took a rigorous, unequivocal approach to the supply-demand balance. In simple terms, as soon as supply is seen to reduce below pre-established margins of safety, corresponding demand management measures must be implemented.
At the core of an effective DRMP is early warning and decisive early action transparently triggered by hydro-meteorological indicators. As Cape Town has now discovered, you must implement tough restrictive measures at the very earliest sign of increasing hazard, not after the situation has gone beyond recovery. This may be politically unpopular, but it is the only correct way to prudently manage the risk. The Kosovo national drought framework rests on two basic but effective early warning indicators, namely the Standardised Precipitation Index (SPI), and Reservoir Rule Curves (RRCs). The first is a meteorological hazard indicator; the second a hydrological one. Neither of these techniques is particularly novel or complex, but the innovation of the Kosovo national framework has been to incorporate these explicitly and simply into a multi-stage drought response framework. Local water companies now have published DRMPs, and routinely monitor precipitation and the related SPI indicator. However, this early warning and response system has yet to be tested against the next significant drought.
Precipitation is always the driving force of the catchment water balance. The indicators for a developing ‘hydrological drought’ e.g. reservoir volumes less than normal, will be evident for several months at least from the preceding ‘meteorological drought’. 5 The effectiveness of the Standardised Precipitation Index (SPI) method as an early warning system for drought onset led the World Meteorological Congress to recommend that the SPI should be adopted by all national hydrometeorological services as one of the principal methods to characterise meteorological droughts. 6
Colour mapping of the SPI across various timescales can be highly effective in communicating developing drought hazard to non-technical stakeholders. Green represents precipitation within ‘normal’ statistical bounds (typically 1 Standard Deviation (s), but when the SPI value reaches -0.84 (Yellow), this is indicative of a moderate meteorological drought for the preceding period being analysed (2, 3, 6 months etc.). Values of -1.5 (Orange) or less indicate a severe meteorological drought, -2.0 an extreme drought (Red).
Kosovo’s experience has shown that in every historical case of where the SPI-4 or SPI-6 (preceding 4 or 6 month period) was less than -0.84, this prolonged precipitation deficit inevitably translated into some degree of hydrological drought, with consequent reductions of inflow into the regional water supply reservoirs. A drought emergency was declared in Kosovo in February 2014, following one of the driest December-January periods on record (SPI-2 = -2.20), but detailed analysis of this drought has shown that its onset could be traced to 22 months previously, and water restriction measures should have been first triggered as early as May 2013 according to simple SPI tracking.7
Kosovo water managers only reacted eight months later when reservoirs reached critical levels (27% of normal), although storage levels had been significantly below normal for many months without sufficient water restrictions being imposed.
The second indicator establishes operating rules for the water supply reservoirs compared to a year of normal storage fluctuation (Green). Four drought risk thresholds are defined, 100%, 75%, 50% and 25% of normal volume. When the 75% threshold is crossed, restrictive action MUST be implemented, and is maintained until the reservoir level is restored above that threshold. If this action fails i.e. the 50% threshold is approached, water restrictions must become increasingly onerous. To continue ignoring the conservation threshold(s) is effectively a high risk gamble on future replenishment of storage that may never materialise. This creates risk of catastrophic hydrological failure.
Both the meteorological (SPI) and hydrological (RRC) indicators are at the centre of the published DRMPs for all Kosovo water companies. They are used in a simple and unequivocal way to trigger various clearly defined and pre-published actions and responses by the regulators, operators and households. The DRMP itself is highly structured, and simply lists precise technical supply and/or demand measures and communication actions to be taken at each stage of severity. Importantly these are always quantifiable or accountable actions. A comprehensive plan extends to only 10 A4 pages, two pages (supply/demand actions + communication plan) for each of the five drought response phases, moving from Normal (Green), through Drought Alert (Yellow), Drought Warning (Orange) to Drought Emergency (Red) and Drought Recovery (Blue).
The DRMP colour scheme is explicitly associated with the equivalent status of the early warning indicators. This unequivocal message communicates powerfully to the general public. The phase of the drought is technically defined, and the consequent restrictive actions have been agreed well in advance by all stakeholders. The lists of restrictive and communicative measures are clearly set out and numbered, providing an audit trail of who is to do what and by when. The DRMP framework is fully scalable i.e. precisely the same indicators and published plan format can be used at national through to municipal or water company level, and for surface or groundwater or conjunctive use systems. This ensures consistent integration of drought risk management at every level.
The message from Prishtina to other water scarce cities in the world is simple: Use simple and consistent drought hazard triggers. Develop a highly structured and communally agreed response plan, setting out unambiguous supply-demand actions and legally enforceable measures at each stage of severity, and stick to them.
- http://www.telegraph.co.uk/travel/destinations/africa/south-africa/cape-town/articles/. Daily Telegraph, February 2018
- https://news.nationalgeographic.com/2018/02/cape-town-running-out-of-water-drought-taps-shutoff-other-cities/, February 2018
- IPCC Fifth Assessment Report Climate Change 2014: WGII – Impacts, Adaptation and Vulnerability, Chapter 3, 2014
- Technical Guidance – Preparation of Water Company Drought Risk Management Plans. GIZ, 2015.
- Wilhite, D.A.; and M.H. Glantz. 1985. Understanding the Drought Phenomenon: The Role of Definitions. Water International 10(3):111–120, 1985.
- World Meteorological Organisation, 2012: Standardised Precipitation Index User Guide.
- Faulkner, B.L. Practical Applications of the Standardised Precipitation Index as a Tool for Very Early Warning of Droughts and Floods in the Balkans Region. Geophysical Research Abstracts, Vol.18 EGU2016-10346. EGU General Assembly 2016.
Brian Faulkner is Principal Consultant at www.waterconsultant.com, specialising in water resources planning, reservoir systems and flood and drought management. He has worked internationally in the field for over 35 years.
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, Oxford University, or any of the institutions to which the authors are associated. Please see the Global Water Forum terms and conditions here.