Part 2.3: Drought

This chapter of the module will enhance your understanding of:

the meaning of the term drought

the causal phenomena leading to drought

the effects of drought on affected communities

the factors affecting vulnerability to drought

drought preparedness and mitigation measures

typical assistance needs

Introduction

Of all the natural disasters, droughts have the greatest potential economic impact and can affect the largest number of people. Earthquakes and cyclones are potentially of enormous physical intensity but are of short duration and geographically limited. The death toll from such disasters can be very high if urban or densely populated rural areas are affected. By contrast droughts affect large geographical areas - often covering whole countries or parts of continents - they may last for months and in some cases several years. They invariably have a direct and significant impact on food production and the overall economy.

DROUGHT HAZARD DATA SHEET

Number of persons killed in drought/food shortage declared disasters from 1980-89: 404,139

Number of persons affected: 101,074,389 (OFDA, 1990)

Selected recent drought disasters

Year	Location	Deaths	Number affected
1982-1987	Botswana	no report	671.000
1987	Ethiopia	367	5-7 million
1987	Somalia	600	500.000
1988	Sudan	250.000	1.750,000
1989	Togo	no report	400.000
1989	Uganda	no report	600.000
1989-90	Angola	10,000	1.9 million
1989-90	Ethiopia	no report	2.3-3.8 million
1990	Bolivia	no report	283,160

Source: OFDA, 1987-90

A general working definition of drought might be a temporary reduction in water or moisture availability significantly below the normal or expected amount for a specified period.

The key components of such a definition are:

a) that the reduction is temporary (if the reduction were permanent then terms such as "dry" and "arid" would be more appropriate)

b) that the reduction is significant

c) that the reduction is defined in relation to a "norm"

d) that the period taken as the basis for the "norm" is specified.

All societies tend to stabilize their socio-economic systems around what is perceived to be the normal rainfall and this perception is heavily weighted towards recent experience.

How the "norm" is measured is of critical importance. Components c) and d) therefore require more detailed clarification. The "norm" may be defined either:

1) technically - for instance, a reduction of water availability might qualify as a "drought" when it falls below 80% of the average availability over the preceding 20 years. However, within naturally fluctuating climate and weather systems the period selected as the basis for estimating the average may be significantly misleading (see figure 2.3.1), or

2) culturally - in terms of the level of water availability around which society has taken to be the "norm". All societies tend to stabilize their socio-economic systems around what is perceived to be the normal rainfall and this perception is heavily weighted towards recent experience. Thus, after a run of perhaps ten years with above average rainfall a society may have become used to the wetter state and perceive the first year of average rainfall as a drought.

Figure 2.3.1 - Schematic presentation of fluctuations occurring on different time scales

Drought types

There are three types of drought: meteorological, hydrological and agricultural. The first two types describe physical events; the third describes the particular impact of the first two types on an area of human activity - agricultural production. It is necessary to carefully distinguish between these types and to clarify their relationships to one another.

Meteorological drought involves a reduction in rainfall for a specified period (day, month, season, year) below a specified amount - usually defined as some proportion of the long term average for the specified time period. Its definition involves only precipitation statistics Care needs to be taken in utilizing and aggregating rainfall data.

Hydrological drought involves a reduction in water resources (streamflows, lake levels, groundwater, underground aquifers) below a specified level for a given period of time. Its definition involves data on availability and offtake rates in relation to the normal operations of the system (domestic, industrial, irrigated agricultural) being supplied.

Agricultural drought is the impact of meteorological and hydrological droughts on this particular area of human activity. Crops have particular temperature, moisture and nutrient requirements during their growth cycle in order to achieve optimum growth. If moisture availability (or indeed any other required input) falls below the optimum amount during the growth cycle, then crop growth will be impaired and yields reduced. Because of the complexity of the relationships involved, agricultural drought is difficult to measure. A fall in yields may be due to insufficient moisture but it may also stem from, or be exacerbated by, such factors as the unavailability of fertilizers, lack of weeding, the presence of pests and crop diseases, the lack of labor at critical periods in the growth cycle, unattractive crop prices, etc. Because of all these other factors capable of affecting yields, it is incorrect to assume that meteorological drought and agricultural drought are synonymous. For the scope of this module we will use the term drought to mean agricultural drought induced by meteorological and hydrological drought.

Q. What are the differences between meteorological, hydrological, and agricultural drought?

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ANSWER Meteorological drought is a reduction in rainfall, hydro-logical drought is a reduction of water resources including lakes, streams, underground aquifers, and groundwater. Agricultural drought is the result of both hydrological and meteorological drought on agricultural practices.

Parched agricultural land

FAO, UNDRO NEWS, May/June, 1989.

Causal phenomena

When discussing the causes of drought it is helpful to distinguish between short drought "episodes" lasting 1-3 years and long dry "regimes" of predominantly subnormal rainfall spanning about a decade or more, which may include several intense drought episodes.

The proximate or immediate cause of rainfall deficit may be due to one or more factors such as an absence of available moisture in the atmosphere; large scale subsidence (downward movement of air within the atmosphere) which suppresses convective activity; and the absence or non-arrival of rain-bearing systems. Changes in such factors involve changes in weather systems ranging from local to regional to global. While it may be possible to indicate the immediate cause of a meteorological drought occurring in any particular location, it is often not possible to indicate the underlying cause.

While it may be possible to indicate the immediate cause of a meteorological drought occurring in any particular location, it is often not possible to indicate the underlying cause.

Short term episodes can often be linked (or "teleconnected") to global-scale fluctuations in the atmosphere and oceans elsewhere in the world. Thus, the El Niouthern Oscillation (ENSO) phenomenon, which involves the periodic invasion of warm surface water into the normally colder waters off the Pacific coast of South America, affects the levels of rainfall in many different parts of the world, including south-eastern Africa. However, understanding the process which causes the invasion of the warmer currents is presently incomplete.

Many causes of long dry "regimes" have been postulated. Among the local level causes are human-induced changes resulting from vegetation loss due to overgrazing and deforestation either in the general vicinity or "upwind" of the area along the line of the prevailing, moisture carrying winds. Such changes may recur and perpetuate the drought conditions.

On a larger spatial scale the link between sea surface temperatures and rainfall has been suggested as a possible cause of the long dry regimes. Thus it has been suggested that the fact that the southern Atlantic has been consistently warmer than the northern Atlantic since around 1970 is related to the predominantly dry period in the Sahel since the mid-1960s.

However, one of the main problems with the theories involving human induced change is that of distinguishing human induced change from natural long term fluctuations. For instance, there would seem to be a fluctuation in rainfall in the western Sahel on a time scale of around 50 years with the predominantly dry period since the mid-1960s being part of such a cycle. However, reliable rainfall data series for the Sahel and many other parts of the world are available only for the last 80-90 years, and this is far too short a period to support the assertion that there is such a rainfall cycle for the area. The World Meteorological Organization believes that five or six such cycles are necessary to confidently predict trends.

Predictability

Whatever the period, the warning time allows for a response by governments to mitigate the impacts of the drought before they become significant.

Of the main natural disasters, droughts are unique in terms of the length of time between the first indications from, for example, rainfall monitoring, that a drought is developing and the point at which it begins to impact significantly upon the population of the affected area. The length of such "warning time" varies significantly between different societies. In many countries the warning time is in the order of several months. In those countries with a high proportion of landless laborers dependent upon crop-related employment the warning time may be much less, perhaps a matter of a few weeks. Whatever the period, the warning time allows for a response by governments to mitigate the impacts of the drought before they become significant. In countries where there is a lead time in the order of months, it is generally possible to mobilize relief assistance, including food aid, from the international community. Thus, by virtue of modern meteorological monitoring and telecommunication systems it has become perfectly possible to prevent excess mortality resulting from food shortages caused by drought alone. Droughts may continue to be a contributory cause of famines but other factors such as conflict and international politics are now invariably responsible for propelling a situation of economic hardship caused by drought into a famine.

During the last two decades, many developing countries have, with donor encouragement and assistance, invested in and improved the coordination of their existing systems for reporting on meteorological, agricultural, crop marketing and such indicators as nutritional status so that they are better able to provide "early warning" information. In most countries such systems have involved the creation of "Early Warning Units" located in an appropriate department of Central Government into which the Meteorological Departments, Agricultural Extension and Statistics Departments feed information. In addition to these national systems there are other "Early Warning Systems" functioning at different levels. Thus, regional groupings such as CILSS (Comitermanent Inter-Etats de Lutte Contre la Secheresse dans le Sahel or Permanent Inter-State Committee for Drought Control in the Sahel) in West Africa, SADCC (Southern African Development Coordinating Conference) have established Regional Early Warning Systems which combine the output of the national systems with information from other sources, such as remote sensing information from satellites.

FAO GIEWS is an important source of information for donor organizations. Within countries there may also be local level "Early Warning Systems". Often these are funded by NGOs and usually, but not always, feed into the government-run National Early Warning Systems.

Factors contributing to vulnerability

In the discussion of factors affecting vulnerability to drought we are referring to agricultural drought. The following factors, then, are those contributing to overall vulnerability to agricultural drought.

The proportion of production which is irrigated

The correlation between rainfall and yields is clearly weaker in irrigated rather than rainfed areas. The extent to which this is the case, however, will be determined by the importance of local rainfall in the irrigated water supply and whether all or only part of the crops' moisture requirements are normally met through irrigation.

Early warning systems

Water pumped from the Niger River for irrigation.

UNDP/Ruth Massey. World Development, Sept. 1989.

The moisture retention capacity of the soil

Different soil types have different capacities to "hold" or retain moisture. For instance the water retention capacity of sandy soils is generally significantly lower than that of clay soils. Soils therefore represent potential short term "stores" of water. In areas where soil moisture retention capacities are high, crop growth may not be affected by prolonged dry periods (as much as 20 days) and some moisture may actually be held over from one wet season to another.

In contrast, in areas where retention capacity is low, dry periods of only a week may result in reduced yields and any moisture present in the soil at the end of one wet season will not be held over to the start of the next. In many arid and semi-arid areas of the tropics the predominant soil types are sandy. To attain optimum crop growth such areas need frequent and evenly spaced rains throughout the growing season.

Timeliness of the rain

Deficiencies in moisture supply at critical stages during the growth cycle (e.g. germination, flowering, etc.) can significantly reduce yields. Consequently the distribution or timeliness of the rainfall during the growing season is potentially as important as the overall amount of rain.

The adaptive behavior of farmers

In the face of an intermittent start to a wet season, some farmers may respond with repeated replantings of the same crop variety to take account of the rains when (and if) they finally start, while others may replant using other varieties. Some farmers may not have seed reserves of their own or be in a position to purchase replacement seeds for the first failed planting, in which case these farmers may experience a crop failure while other farmers in the same area may enjoy a satisfactory harvest.

The effects of drought

L. AnstrUNDRO News, Jan/Feb. 1985

Typical adverse effects

Typical adverse effects of agricultural drought include the following:

Reduced income for farmers

Reduced employment opportunities for agricultural laborers

Reduced demand within the economy generally

Increased defaulting on loans in the rural sector (central and commercial banks)

Reduced government revenues and foreign exchange earnings as a result of a decline in agricultural exports

Increased price of staple foods

Increased inflation rate within the economy

Inability of certain groups within the population to afford increased food prices results in their:

- switch to cheaper and sometimes less preferred foods
- reduction in overall food intake
- borrowing/taking loans in order to maintain food intake
- selling their assets to raise funds
- engaging in alternative income earning activities locally
- migrating in search of employment opportunities elsewhere
- migration to where relief food is being distributed

Increased stress and morbidity due to migration journey

Reduced food intake leads to deterioration of nutritional status and reduction in ability to resist infection

Drying-up of water sources leads to reduction in water quality, the need to travel further to collect water and possibly to migrate to better water sources, all of which are likely to increase levels of morbidity

Increased competition for access to remaining water sources may lead to increased incidence of local disputes/conflict

Social costs caused by migration, e.g. break-up of communities and families

Q. What are the basic factors contributing to vulnerability from drought?

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ANSWER The basic factors contributing to the vulnerability to drought are: - the proportion of agricultural production which is irrigated - the moisture retention capacity of the soil - the timeliness of the rain - the adaptive behavior of the farmers

Possible risk reduction measures

To reduce the risk of transitory food insecurity due to drought, it is necessary to protect people's access to food through

1) ensuring the availability of food in the affected area and
2) protecting the entitlements of all groups within the affected population.

Some of the principle measures for maintaining food security during agricultural droughts are:

price stabilization

food subsidies

employment creation programs

general food distributions

supplementary feeding programs

special programs for livestock and pastoralist populations

complementary water programs

complementary health programs

Preparedness measures

Preparedness for drought requires that additional response capacity be sustained within the system.

Preparedness for drought requires that additional response capacity be sustained within the system. Where governance is poor such capacity is unlikely to be maintained between episodes of transitory food insecurity due to drought.

Several UN agencies are involved in responding to transitory food insecurity and famines. The greater part of resources channelled through the UN in response to such situations are via WFP (food aid), UNHCR (all forms of assistance for refugees) and UNICEF (non-food relief, but especially health and water supply with a focus on women and children as priority groups).

The proliferation and increasingly important role of NGOs has a number of implications. Where the government or UN has established effective coordination mechanisms and the number of NGO programs in the country in response to the emergency is limited, coordination amongst the NGO community may be adequate. Where government and UN coordination mechanisms are weak and there is a significant increase in the number of NGOs working in the country, significant coordination problems may arise. While in the short run the use of NGOs may be necessary in the interests of ensuring a prompt and effective response to the population in the affected area, care should be taken to ensure that the use of NGOs does not prevent the longer run efforts to strengthen the capacity of government agencies.

Care should be taken to ensure that the use of NGOs does not, prevent the longer run efforts to strengthen the capacity of government agencies.

Typical post disaster assistance needs

The affected population must be assisted to replace assets lost during the period of temporary food insecurity and, where this is realistic, to reestablish their livelihoods. The severity of this food insecurity episode will determine the nature and scale of the rehabilitation requirements. Thus, if migration to camps and significantly increased mortality has occurred, then a comprehensive rehabilitation program will be required. This may involve health care, counseling, assisting the migrants back to their homes and material support to re-establish their homes and productive activities. Such provisions may include seeds, tools, cooking utensils, blankets, and support until households are capable of supporting themselves. If the impact of the temporary food insecurity episode has not been severe and most households have not been obliged to sell productive assets (e.g. consume seed stocks and breeding livestock) then a rehabilitation program may not be required.

Rehabilitation needs should therefore be carefully assessed and interventions tailored to the particular situation.

CASE STUDY

Timbuktu

Rehabilitation With Rice

During the drought years of the early 1980s, Songhai farmers, living near Timbuktu in Mali, became destitute. The Niger River which had annually overflowed to flood the farmers' lowland fields failed. Dust storms raged, wells dried up, and the river reached the lowest levels ever recorded. The farmers became victims of the long dry spell that forced them to relinquish their traditional way of life and to seek jobs in local towns for the survival of their families.

In 1984, the United Nations Capital Development Fund (UNCDF) assisted 13,000 inhabitants of the villages of Timbuktu and Gao to grow a new type of irrigated rice in the desert with water pumped from the Niger River. Pipes hundreds of meters long were installed and a revolving fund established to purchase seeds, pesticides, fuel and spare parts for the pump. The project was assisted by three UN volunteers using a new high yielding hybrid rice crossed from the traditional floating rice to the much higher yielding Asian irrigated rice.

When the project began to produce 1,800 kilos of rice per hectare, 15 more villages formed similar associations to those at Gao and Timbuktu. The new irrigation system allowed two crops per year instead of the traditional annual crop.

The project, however, was not trouble free. The farmers were promised an incentive of 5 kilos of maize for each tree planted as a shelter crop for the rice. Although beneficial to both the environment and the crop, the trees were not watered and died after the local authorities failed to deliver the maize as promised.

Bookkeeping also proved to be a problem. The Songhai do their accounting in their heads, a practice which is difficult to monitor, especially when accounting expands from the repayment of simple debts between farmers to balance sheets for large cooperatives. On the whole, however, the development of the communities involved has attested to the success of the project. Many villagers also attended literacy classes and other training.

Q. What are the strong points of this project? What are the weak points? If another drought occurs, what effects may it have on the irrigation system?

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Soeters, R. 1988. "Pitfalls with weight-for-height measurements in surveys of acute malnutrition". Tropical Doctor 16(4), 174-176.

Wilhite, D.A. and Glantz, M.H. 1985. "Understanding the Drought Phenomenon: The Role of Definitions". Water International 10,111-120.

World Bank. 1986. Poverty and Hunger: Issues and options for food security in developing countries. Washington D.C.

WHO (World Health Organization). 1985. "Energy and Protein Requirements" Report of a Joint FAO/WHO/UNU Expert Consultation, Technical Report Series 724, Geneva.

WMO (World Meteorological Organization). 1983. "Report of the Expert Group Meeting on the Climate Situation and Drought in Africa". Geneva: WCP-61.

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