Basics

Figure 1: Climate Calendar in Sri Lanka

Drought is an insidious hazard of nature. It is often referred to as a "creeping phenomenon" and its impacts vary from region to region. Drought can therefore be difficult for people to understand. It is equally difficult to define, because what may be considered a drought in, say, Bali (six days without rain) would certainly not be considered a drought in Libya (annual rainfall less than 180 mm). In the most general sense, drought originates from a deficiency of precipitation over an extended period of time--usually a season or more--resulting in a water shortage for some activity, group, or environmental sector. Its impacts result from the interplay between the natural event (less precipitation than expected) and the demand people place on water supply, and human activities can exacerbate the impacts of drought. Because drought cannot be viewed solely as a physical phenomenon, it is usually defined both conceptually and operationally.

Conceptual definitions, formulated in general terms, help people understand the concept of drought. For example:

Drought is a protracted period of deficient precipitation resulting in extensive damage to crops, resulting in loss of yield.

Conceptual definitions may also be important in establishing drought policy. For example, Australian drought policy incorporates an understanding of normal climate variability into its definition of drought. The country provides financial assistance to farmers only under “exceptional drought circumstances,” when drought conditions are beyond those that could be considered part of normal risk management. Declarations of exceptional drought are based on science-driven assessments. Previously, when drought was less well defined from a policy standpoint and less well understood by farmers, some farmers in the semiarid Australian climate claimed drought assistance every few years.

Operational definitions help define the onset, severity, and end of droughts. No single operational definition of drought works in all circumstances, and this is a big part of why policy makers, resource planners, and others have more trouble recognizing and planning for drought than they do for other natural disasters. In fact, most drought planners now rely on mathematic indices to decide when to start implementing water conservation or drought response measures.
To determine the beginning of drought, operational definitions specify the degree of departure from the average of precipitation or some other climatic variable over some time period. This is usually done by comparing the current situation to the historical average, often based on a 30-year period of record. The threshold identified as the beginning of a drought (e.g., 75% of average precipitation over a specified time period) is usually established somewhat arbitrarily, rather than on the basis of its precise relationship to specific impacts.
An operational definition for agriculture might compare daily precipitation values to evapotranspiration rates to determine the rate of soil moisture depletion, then express these relationships in terms of drought effects on plant behavior (i.e., growth and yield) at various stages of crop development. A definition such as this one could be used in an operational assessment of drought severity and impacts by tracking meteorological variables, soil moisture, and crop conditions during the growing season, continually reevaluating the potential impact of these conditions on final yield.
Operational definitions can also be used to analyze drought frequency, severity, and duration for a given historical period. Such definitions, however, require weather data on hourly, daily, monthly, or other time scales and, possibly, impact data (e.g., crop yield), depending on the nature of the definition being applied. Developing a climatology of drought for a region provides a greater understanding of its characteristics and the probability of recurrence at various levels of severity. Information of this type is extremely beneficial in the development of response and mitigation strategies and preparedness plans.

Research in the early 1980s uncovered more than 150 published definitions of drought. The definitions reflect differences in regions, needs, and disciplinary approaches.
Wilhite and Glantz1 categorized the definitions in terms of four basic approaches to measuring drought: meteorological, hydrological, agricultural, and socioeconomic. The first three approaches deal with ways to measure drought as a physical phenomenon. The last deals with drought in terms of supply and demand, tracking the effects of water shortfall as it ripples through socioeconomic systems.

1. Meteorological Drought

Sequence of drought occurrence and impacts for commonly accepted drought types. All droughts originate from a deficiency of precipitation or meteorological drought but other types of drought and impacts cascade from this deficiency. (Source: National Drought Mitigation Center, University of Nebraska-Lincoln, U.S.A.) Meteorological drought is defined usually on the basis of the degree of dryness (in comparison to some “normal” or average amount) and the duration of the dry period. Definitions of meteorological drought must be considered as region specific since the atmospheric conditions that result in deficiencies of precipitation are highly variable from region to region. For example, some definitions of meteorological drought identify periods of drought on the basis of the number of days with precipitation less than some specified threshold. This measure is only appropriate for regions characterized by a year-round precipitation regime such as a tropical rainforest, humid subtropical climate, or humid mid-latitude climate. Locations such as Manaus, Brazil; New Orleans, Louisiana (U.S.A.); and London, England, are examples. Other climatic regimes are characterized by a seasonal rainfall pattern, such as the central United States, northeast Brazil, West Africa, and northern Australia. Extended periods without rainfall are common in Omaha, Nebraska (U.S.A.); Fortaleza, Ceará (Brazil); and Darwin, Northwest Territory (Australia), and a definition based on the number of days with precipitation less than some specified threshold is unrealistic in these cases. Other definitions may relate actual precipitation departures to average amounts on monthly, seasonal, or annual time scales.

2. Agricultural Drought

Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, focusing on precipitation shortages, differences between actual and potential evapotranspiration, soil water deficits, reduced groundwater or reservoir levels, and so forth. Plant water demand depends on prevailing weather conditions, biological characteristics of the specific plant, its stage of growth, and the physical and biological properties of the soil. A good definition of agricultural drought should be able to account for the variable susceptibility of crops during different stages of crop development, from emergence to maturity. Deficient topsoil moisture at planting may hinder germination, leading to low plant populations per hectare and a reduction of final yield. However, if topsoil moisture is sufficient for early growth requirements, deficiencies in subsoil moisture at this early stage may not affect final yield if subsoil moisture is replenished as the growing season progresses or if rainfall meets plant water needs.

3. Hydrological Drought

Hydrological drought is associated with the effects of periods of precipitation (including snowfall) shortfalls on surface or subsurface water supply (i.e., streamflow, reservoir and lake levels, groundwater). The frequency and severity of hydrological drought is often defined on a watershed or river basin scale. Although all droughts originate with a deficiency of precipitation, hydrologists are more concerned with how this deficiency plays out through the hydrologic system. Hydrological droughts are usually out of phase with or lag the occurrence of meteorological and agricultural droughts. It takes longer for precipitation deficiencies to show up in components of the hydrological system such as soil moisture, streamflow, and groundwater and reservoir levels. As a result, these impacts are out of phase with impacts in other economic sectors. For example, a precipitation deficiency may result in a rapid depletion of soil moisture that is almost immediately discernible to agriculturalists, but the impact of this deficiency on reservoir levels may not affect hydroelectric power production or recreational uses for many months. Also, water in hydrologic storage systems (e.g., reservoirs, rivers) is often used for multiple and competing purposes (e.g., flood control, irrigation, recreation, navigation, hydropower, wildlife habitat), further complicating the sequence and quantification of impacts. Competition for water in these storage systems escalates during drought and conflicts between water users increase significantly.

4. Socioeconomic Drought

Socioeconomic definitions of drought associate the supply and demand of some economic good with elements of meteorological, hydrological, and agricultural drought. It differs from the aforementioned types of drought because its occurrence depends on the time and space processes of supply and demand to identify or classify droughts. The supply of many economic goods, such as water, forage, food grains, fish, and hydroelectric power, depends on weather. Because of the natural variability of climate, water supply is ample in some years but unable to meet human and environmental needs in other years. Socioeconomic drought occurs when the demand for an economic good exceeds supply as a result of a weather-related shortfall in water supply. For example, in Uruguay in 1988–89, drought resulted in significantly reduced hydroelectric power production because power plants were dependent on streamflow rather than storage for power generation. Reducing hydroelectric power production required the government to convert to more expensive (imported) petroleum and implement stringent energy conservation measures to meet the nation’s power needs.
In most instances, the demand for economic goods is increasing as a result of increasing population and per capita consumption. Supply may also increase because of improved production efficiency, technology, or the construction of reservoirs that increase surface water storage capacity. If both supply and demand are increasing, the critical factor is the relative rate of change. Is demand increasing more rapidly than supply? If so, vulnerability and the incidence of drought may increase in the future as supply and demand trends converge.

1Wilhite, D.A.; and M.H. Glantz. 1985. Understanding the Drought Phenomenon: The Role of Definitions. Water International 10(3):111–120.

5. Ecological Drought

A more recent effort focuses on ecological drought, defined as "a prolonged and widespread deficit in naturally available water supplies — including changes in natural and managed hydrology — that create multiple stresses across ecosystems."

Multihazard Risks in Sri Lanka This case study exemplifies a high-resolution assessment of natural hazards, vulnerability to hazards, and disaster risk. Drought, flood, cyclone, and landslide hazards, as well as vulnerability to those hazards, were identified using data from Sri Lankan government agencies. Drought- and flood-prone areas were mapped using rainfall data that were gridded at a resolution of 10 kilometers. Cyclone and landslide hazards were mapped based on long-term historical incidence data. Indexes for regional industrial development, infrastructure development, and agricultural production were estimated on the basis of proxies. An assessment of regional food insecurity from the World Food Programme was used in the analysis. Records of emergency relief were used in estimating a spatial proxy for disaster risk. A multihazard map was developed for Sri Lanka based on the estimates of regional drought, flood, cyclone, and landslide hazards. The hazard estimates for drought, floods, cyclones, and landslides were weighted for their associated disaster risk with proxies for economic losses to provide a risk map or a hotspots map. Principal findings include the following:

1. Useful hazard and vulnerability analysis can be carried out with the type of data that is available incountry. The hazard estimates for droughts, floods, cyclones, and landslides show marked spatial variability. Vulnerability shows marked spatial variability as well. Thus, the resolution of analysis needs to match the resolution of spatial variations in relief, climate, and other features. Analyses of disasters need higher spatial and temporal resolution for planning and action at the local level.
2. Multihazard analysis brought out regions of high risk such as the Kegalle and Ratnapura districts in the southwest; the Ampara, Batticaloa, Trincomalee, Mullaitivu, and Killinochchi districts in the northeast; and the districts of Nuwara Eliya, Badulla, Ampara, and Matale, which contain some of the sharpest hill slopes of the central mountain massifs.
3. There is a distinct seasonality to risks posed by drought, floods, landslides, and cyclones. Whereas the eastern regions have hotspots during the boreal fall and early winter, the western-slopes regions are risk prone in the summer and the early fall. Thus, attention is warranted not only on hotspots but also on “hot seasons.”
4. Climate data were useful for estimating the degree of hazard in the case of droughts, floods, and cyclones and the risk of flood and landslide. The methodologies used here for hazard analysis of floods and droughts present an explicit link between climate and hazard. This link can be used in conjunction with seasonal climate prediction to provide predictive hazard risk estimates in the future.
5. Climatic, environmental, and social changes such as deforestation, urbanization, and war affect hazard exposure and vulnerability. It is more difficult to quantify such changes than the baseline conditions. However, climate change is already making parts of the island more prone to drought hazard.

a. Agriculture

Sri Lanka has been traditionally an agricultural country and the majority of its citizenry still depend on it for livelihoods, nutrition and food security. While many thousands of farmers and traders directly benefit from agriculture many millions locally and globally provide demand for agricultural products. The climate is a key factor in agriculture. As we have experienced in Sri Lanka of late, with floods on one hand and droughts on the other stress the agricultural land and plants there is much distress. This distress is found in the many cries of the farmers who depend upon farming as livelihood. There have been tendencies of psychological stress, suicides and more youth foregoing the agricultural craft and livelihoods of their parents which also spell distress to the society. This distress is also found in Governmental expenditure for relief services used for mitigating the effects of such natural disasters. This makes a deeper indent on the country’s financial reserves for food imports. Sri Lanka already has a massive debt based on technology and commercial ventures and along these lines, when the country would also contribute to debt in agriculture, the national debt is deepened. This could lead to political repercussions with the country favouring some products from some countries as mitigation measures where this move is understood as a country going back on the traditional farming industries and substituting it with cheaper produce and neo colonial economic order.

b. Health

Drought is defined as the absence of an average rainfall over a sustained period of time. Often drought is associated with warmer temperatures – this leads to greater evaporation- leading to loss of water for use and consumption As we all know water is essential for human survival. Throughout human histories humans have made dwellings near water surpluses and when it has been lost there has been threats to societal survival issues such as due to desertification . Drought directly affect availability and access to drinking water. Drinking water is probably the most vital of all the water needs humans and directly affects human health. In its absence there is causes for excessive thirst, dehydration, renal problems and in a final stage the failure of bodily systems. When drought conditions persist there is also the threat of water contamination which may also lead to several health hazards. With the onset of a drought and the lessening of water supplies there is also the social dilemma of relief efforts versus long term implementations. Water is a main ‘ingredient’ in cooking can lead health complications due to inadequate and improper washing and cleaning In households such as in the hills and in remote villages which rely on fetching of water, the drying up of water sources, the failures of water supply scheme and shortage of water can lead to problems of sanitation and hygiene particularly for women and girls who are usually tasked with fetching water in these settings. Climate has a direct role (including through its influence on the water cycle) in transmission of infectious diseases such as Malaria, Dengue, Tuberculosis, and Leptospirosis. In recent times, the rise of the Dengue has also been linked with drought conditions and prolonged temperature increases. The mechanisms behind CKDU kidney disease is under scientific debate – however, it is male farmers in particular who are exposed to extreme heat and undergo larger losses of fluids who have been stricken. The climate link is being sorted out. Drought thus imposes further demands on already over-burdened health services and on people. In particular, It adds to the vulnerability of children, elders and pregnant mothers who come from sheltered environments.

c. Energy

Sri Lanka still depends on hydro power primarily for about 40% of its electricity generation. Its over-extended electric system is critically dependent on the hydropower systems to meet peak night time demands for electricity. By monitoring and anticipating drought, water allocation may be done to preserve water for peak demands. Alternative sources of energy generation may be seasonally prioritized – e.g. maintenance may be rescheduled or additional fuel stockpiles pre-positioned. Climate directly affects streamflow primarily through rainfall and indirectly through evaporation and evapotranspiration. Drought leads to drop in electricity generation. Note that the climate across Sri Lanka can vary – we may have more rain for example on the Eastern slopes in some seasons while having drought elsewhere.

The Social and Economic Impact of Drought on Electricity Planning

With the country becoming more industrial and service oriented, hydro-electricity facilitated the supply over the years to even 84% of the national electricity needs 25 years back. As the electricity demands have risen, , the prospects of viable new medium to large scale hydropower generation plants have become nearly exhausted. When there is shortage of water there is the prospect of low electricity generation and load shedding. The harmful impacts flow from the family level right to the national level. . When electricity shortages aThis can account for loss of GDP and income while also making the acute problem of unemployment severe. results it may also affect livelihoods based on certain industries. There can be a shortfall of electricity for essential services such as hospitals. to emergency services Drought directly affects the extent of hydropower generation. Hydropower at present while only meeting about 40% of the needs however is essential to meet the current demands due to overstressed systems and the constant breakdowns at the Coal Power Plant at Norochcholai. In particular, it is relied on to store “energy” and to meet the night time peak loads – which are extremely expensive to meet in other ways.

Energy Policy and Climate

Overall though the electric grid is only a fraction of energy generation – the larger contributors are the direct use of solar radiation and biomass. These too are directly affected by the climate – though in different ways than hydropower generation. A “smart grid” can make use of this. The biggest low-hanging fruit for Sri Lanka is trying to reduce waste and losses of energy. Energy conservation measures in government and private organizations can reduce losses by about 50% or more. The electric transmission lines of the Ceylon Electricity Board loses 20% of the energy generated – which is excessive. Systematic energy audits, monitoring, education and enforcement and awareness and citizen action can reduce the need for electricity. Much use can be still made of alternative energy sources – directly the sun and biomass - rather than moving too quickly and easily to use of the grid. For example, through traditionally inspired housing designs can reduce the need for air-conditioning which is often the biggest component of electric load. More open designs can reduce the need for artificial lighting. Trees and curtains can substantially cut down on electric needs for ventilation and cooling. In addition, renewable sources of energy such as solar capture, wind energy, and mini-hydropower plants are making a small but growing contribution at present. All of these are sources for the future.

The Consequences of Drought on Energy Politics

Energy shortfalls induces political pressure on the governments into facilitating coal and thermal fuel power plants. This measure along pollution, allocations of vast land and unethical land acquisitions, marine, inland aquatic and atmospheric pollution which in turn also provide more communal distress than it provides relief. The coal power power plants that we have already initiated have faced severe criticism from environmental groups who have even questioned the professional opinions of ‘experts’ who have even miscalculated the direction of the wind! This raises eyebrows as these natural disasters are even politicized while the affected people yearn only for that what is needed for survival.

d. Environment

In maps, drought is often marked with bright red and brown which gives a disfigured impression of the opposite of green or blue. In reality it is exactly what happens to our surrounding when there a long period water absence.

Flora: There is more reason for trees and plants which are not agricultural to suffer even succumb to the effects. This makes forest cover disappear and the possibility of fires which could be intentional or natural.

Wildlife: Wildlife similarly to humans depend on water for existence. There could be competition for water sources, disappearance of some animal species as well as conflicts with humans. While the majestic elephant is symbol of Sri Lankan pride such is not the scene in areas there they are not able to nourish themselves and they almost at most times entangle themselves in village supplies of food and water. This has also made way to somewhat unethical and brutal suffering of animals. On the other hand many lives and stock has also been destroyed by these animals who struggle to survive. Drought targets water sources naturally and when water sources home many species of fish and aquatic animals their survival also is jeopardized.

Coastal Impacts: There could also be oceanic impact particularly on the coastal ecosystem – drought affects when sandbars break (e.g. in Batticaloa) affecting the lagoon and its livelihoods. It affects saltwater intrusion into the rivers. Often drought is associated with warmer temperatures. Warmer sea temperatures can lead to impacts on the coastal ecosystem such as on corals. Coral bleaching has become exacerbated due to both the seasonal to inter-annual variability on top of the warming Arabian seas.