World Bank Institute
Provention Consortium
Disaster Management Facility
Pilot Course on Urban Risk Management in Latin America: Disaster
Prevention
Panama City, Panama, 13 - 16 March 2003
EXERCISE TO VALUE THE IMPACT OF THE 2001 DROUGHT ON THE DRINKING
WATER SERVICES IN A CITY OF 40,000 INHABITANTS
Translation of materials prepared by Mrs. J. Roberto Jovel, Consultant to ECLAC
2
BACKGROUND INFORMATION: DAMAGE CAUSED BY DROUGHT IN CENTRAL
AMERICA IN 2001
1. THE 2001 DROUGHT IN CENTRAL AMERICA
Between the months of May and October 2001 Central America suffered an abnormal
hydro meteorological event due to a reduced rainfall level well below the average of
historical records as well as in regards of the water supply needs of the population and
to provide regularly production and services..
Rainfall in the Pacific side of the Central American Isthmus has a well established and
documented dry season between November and April each year. This is followed by a
rainy season from May to October. The months of July and August normally have a
diminished rainfall which is known as recognized as a brief summer season (canícula
o veranillo), resuming higher levels of precipitation in September and October. On
the contrary, the Atlantic or Caribbean side of the region only experiences diminished
rainfall from January to April.
In 2001 drought ensued since vast extensions both in the Pacific and Atlantic basins
had diminished precipitation as is shown below1.
Figure 1. Central American Map, showing areas affected by drought in 2001
Paradoxically, in most part of the Central American region the year’s amount of
precipitation was nevertheless very close to the historical average. The drought was
caused by an uneven distribution of rainfall among regions and over time during the
year. The years rainy season began with above normal precipitations in May;
experienced a shar reduction in June and the next two months had below average
rainfall; and frm September onward –with localized exceptions— rain was above the
1
Map adapted from Ramírez, Patricia et al, Condiciones de sequía observadas en el Istmo
Centroamericano en el año 2001, Comité Regional de Recursos Hidráulicos, San José, Costa Rica, 2001.
3
historical average as an indirect effect of Hurricane Michelle2. Drought came in the
aftermath of the negative impact of the so-called “coffee crisis” caused by the sharp
drop in export prices, which aggravated th pre-existing nutritional deficit in
vulnerable population groups located in different parts of the sub region.
2. EFFECTS ON THE AGRICULTURAL SECTOR
Millimeters
per month
The less than half of the average rainfall in the middle of the rainy season coincided
with the agricultural cycle’s growing phase of grains basic to the Central American
population’s diet. Water need for non-irrigated crops was not provided given the
precipitation levels durign that period (See figure 2)3. Consequently crops were lost or
had considerably reduced yields, affecting particularly crops produced for selfconsumption.
500
400
300
200
100
0
MAY JUN
JUL AGO SEP OCT
Maize
Beans
Rice
Effective precipitation
Figure 2. Comparison of water required by basic grains with actual rainfall registered (Station in Granada,
Nicaragua, 2002)
The population groups most affected by the climatic variation were those that
cultivate these grain crops for self-.consumption, as noted, and which experienced growing
levels of food and nutritional deficiencies prior to the 2001 drought. These groups
supplement their incomes in order to buy food till they harvest their second crop by looking
for employment picking coffee during the harvesting period.
2
This hurricane affected directly the Caribbean islands of Cuba and Jamaica, where it caused
considerable damage.
3
Effective precipitation is estimated at 80%, the rest normally flowing or filtering to the topsoil.
Required water needs for crops are estimated on the basis of the usual planting and harvesting periods, using a
methodology described in Jovel, Roberto y Martínez, Héctor, El cálculo del uso consuntivo, Water Resources
Departement, Ministry of Agriculture and Animal Husbandry, San Salvador, 1964, and in Jovel, Roberto, El
cálculo de los requerimientos de agua para la irrigación en Costa Rica, Publication No. 39, Central
American Hydrometeoroglogical Project, OMM, San José, 1968.
4
Due to the previous year’s coffee
crisis, peasants and laborers could not
obtain the necessary cash income, which
led to a quasi-famine situation in some
areas of Nicaragua, Honduras, El
Salvador and Guatemala. Timely
interventions from governments and
some international organizations in
providing food aid warranted a less
severe problem, although not enough to
avert population migrations within the
affected countries and among them,
looking for work and food.
3. THE ENERGY SECTOR
Electricity generation had to be reduced due
to the alteration of the rainy season. In
addition to the growing vulnerability of
hydroelectric plants associated with their
diminished water retention capacity derived
from poor watershed management and
sedimentation in the reservoirs caused by
the extreme effects of Hurricane Mitch, lack
of made levels of retention in the reservoirs
drop dramatically. To face this situation and
in order to preserve generating capacity
during the 2002 dry season, generation was increased in thermoelectric plants, whose
operating costs are substantially higher and deficit countries imported from neighboring
ones with some exceeding capacity, benefiting from the existing interconnected grid.
In spite of these efforts and the increased precipitation in October and November
associated with some hurricanes in the Caribbean as noted, in some cases levels in
reservoirs did not reach their normal or average levels, thus requiring continued
dependence on thermal plants. This is illustrated by the graph in figure 3.
Level of reservoir, msnm
5
290
280
270
260
250
240
JAN FEB MAR APR MAY JUN
Projected level
JUL AGO SEP OCT
Actual level
Figure 3. Comparison of actual and projected level in the El Cajón dam in Honduras, during 2001
Since billing of electricity almost automatically adjust to energy market prices, in
most countries the higher cost of generation was transferred to consumers, tus affecting
domestic finances and production costs of businesses.
4. DRINKING WATER AND DRAINAGE
The water an sanitation sector was affected by the drought
through the aggravation of pre-existing poor conditions of water
supply for human and industrial consumption. In some urban
centers—most particularly in the case of Tegucigalpa in
Honduras—rationing was necessary starting in May 2001,
supplemented by water supply using trucks and pipes to large
population groups. This impacted the financial situation of
supplying enterprises given
the higher operating costs and
reduced billing. In addition to the rationing during the
year, the Tegucigalpa situation deteriorated even further
since the reservoirs and dams did not reach their normal
levels at the end of the rainy season, resulting in reduced
supply the following year.
Other urban areas highly dependent on
underground sources and wells have suffered minor problems, mostly due to the fact that
these sources experience a lag between reduced rainfall and water accumulation. In rural
areas most superficial wells dried and had to be deepened in order to maintain normal
supply. In other cases water had to be collected from further, more distant sources, which
was reflected on women’s increased workload, since they are normally in charge of these
tasks.
6
It must be stressed that damatge in the water supply and sanitation system have a
direct impact on the health conditions of the population, especially when the rationing
period is prolonged.
5. TOTAL DAMAGE OF THE 2001 DROUGHT
Estimates made by ECLAC show total losses of the 2001 drought in the six Central
American countries (including Panama but not Belize) to have reached 189 US millions of
dollars4. Of that amount, 125.5 millions (66%) were production losses both in agriculture
and industry; 50.1 millions associated with increased costs and reduced income of
enterprises providing water and electricity; and 13.4 millions (the remaining 7%) reflecting
the emergency costs incurred and humanitarian assistance received.
Distribution of damage, by countries, was the following:
Table 1
Summary of damage caused in Central America by the 2001 drought
(Millions of US dollars)
Sector
Costa
Rica
...
...
8.8
...
--
Agriculture
Industry
Electricity
Water and
sanitation
Emergency
Total
8.8
Per capita
2.14
Source: ECLAC estimates
El
Salvador
25.5
1.6
3.7
...
0.6
Guatemala
Honduras
Nicaragua
Panama
Sub region
12.3
2.3
6.9
-0.9
32.3
5.4
7.2
3.1
3.5
29.1
4.9
6.3
-8.4
11.3
0.9
13.7
0.4
...
110.4
15.1
46.6
3.5
13.4
31.4
5.98
22.4
1.92
51.5
7.29
48.7
8.54
26.3
9.10
189.0
4.80
As shown in the table, countries most affected were Honduras and Nicaragua, and
the most affected activity was basic food production, followed by electricity production. In
per capita terms, Panama, Nicaragua and Honduras experienced most negative effects. It is
important to note that an estimated 600,000 people were primarily affected due to crop
losses, reduced incomes and lower food intake and nutritional levels, to the point of
requiring food aid to survive and medical attention in many instances. Peasant population
already affected by a recent succession of diverse extreme climatic events – hurricanes,
floods, drought – have seen their vulnerability increased to the point of loosing their scarce
assets and production of their home gardens that normally allow them to precariously
survive. Of these, a large number are women and children.
Additionally, over 1.8 million persons were secondarily affected by not having
enough water supply both in urban and rural areas, and in a more severe case in the instante
of Tegucigalpa-Comayagüela, which posed the menace of ensuing sanitary problems later.
4
See in this respect CEPAL - CCAD, El impacto socioeconómico y ambiental de la sequía de 2001
en Centroamérica, Mexico, February 2002.
7
Finally, at the tertiary level, a total of 23 million had to face higher energy costs due to
insufficient hydroelectric generation. Thus, disregarding some possible duplication, the
drought affected, in one way or another, 23.6 millions in the Central American subregion,
that is to say 70% of the total population.
8
II. EXERCISE TO ESTIMATE DAMAGE CAUSED BY DROUGHT IN A CITY
1. Purpose of the exercise
With the background of damage caused by the 2001 drought in the Central American sub
region, which were diverse and widespread in geographical terms, a theoretical exercise
was developed to use for training in this workshop, base don available information of the
drought’s effects. Additionally, the exercise will provide participants with the necessary
tools to face a real evaluation event.
In the following sections the theoretical exercise is described in detail. Participants
in the training workshop will apply the methodology described in the updated and
expanded ECLAC handbook, to process the basic information presented here.
2. Description of the exercise
Pre-disaster conditions
A city of 40,000 inhabitants, located in the Pacific Central American coast has water supply
a reservoir with a compact wall and five deep wells. The reservoir water flows by gravity
through 250 mm. diameter PVC pipe to the water treatment plant, while the wells are
located around the plant, discharging directly to it.
The wells have an average yield of 6 liters per second and operate on a 10 hour
daily basis, providing a total combined supply of 1 million liters per day. The reservoir has
a regulated flow ranking from 5.1 to 6.9 million liters per day, depending on the season and
demand.
Average demand of the city is less than 6 millions de liters daily, which translates
into 150 liters daily per person. Seasonal variations are shown in the figure 4.
Figure 4
Yearly water demand in the city
(Millions of liters per day)
Millions of liters per day
8
7
6
5
4
3
2
1
0
J
F
M
A
M
J
J
A
S
O
N
D
9
Operational revenue of the enterprise during an average month was estimated at
US$ 18,665, which was added to the government’s subsidy of US$ 2,500 per month.
Expenditure fluctuated in average as is shown in the following table based on the most
recent financial statements:
Operational item
Revenues
- tariff billing
- government subsidy
Operating expenditure
- Of the reservoir
- Of the wells
- Of the treatment plant
- Of the distribution network
Other expenditure
- administration
- debt service
Operational results
Monthly figures, US$
21,165
18,665
2,500
13,007
2,842
1,675
2,125
6,365
7,375
3,935
3,440
783
Drought impact on the system
At the beginning of the 2001 rainy
season the level of the reservoir which
provides most of water to the aqueducts
was already at its lower level. May rains
were normal, so that month’s supply was
the usual one. With the precipitation
drop in June and the rest of the rainy
season, the water supply company
decided to reduce supply as long as the
reservoir’s level remained under the
expected level. Additionally, starting in
June the enterprise decided to increase
the operating hours of the well system,
increasing it to 15 hours per day, which increased the supply from this source, but did not
fully compensate the reservoir’s deficit.
October and November’s rainfall, though abundant as an indirect effect of some
tropical storms and Caribbean hurricanes, was insufficient to replenish the reservoir to the
level needed to maintain normal supply of water during the following dry months.
As a consequence, the company decided to reduce the
flow from the reservoir, continue operating the wells at the rate
of 15 hours per day, and order the drilling and tooling of four
additional wells. These wells were dug to a 50 meters depth
with a pipe 20 cm. in diameter. They were equipped with
submersible pumps capable of delivering a flow of 6 liters per
second and raise it to a total dynamic charge level of 40 meters,
10
combined with a 12 HP electric motor with auxiliary electric equipments of 45 KVA. These
equipment was all located in a small shed in the immediate vicinity of the water treatment
plant and directly connected to it.
Two of the new wells started operating in February at almost the described level.
The other two came on stream a month later.
May and June rainfalls were above normal levels and the medium term
meteorological forecast indicated a return to average levels for the remainder of the year,
thus overcoming the water insufficiency experienced by the water system.
Water rationing for the population
As indicated, the reservoir’s operation was reduced since June and the well operating hours
was increased, given the significant precipitation reduction that started that month. That
led to a water supply average of 3.3 millions per day, which resulted in providing service at
an average a little over 12 hours a day.
In July, August and September precipitation improved slightly in comparison to the
preceding month, but not enough to allow increasing the reservoir’s flow to normal levels,
which was reflected in supplying water for 17 to 18 hours per day.
In spite of the improved precipitation during October and November, water supply
had to be rationed from 14 to 16 hours per day. Although the reservoir’s level did not reach
its anticipated level when rains stopped, the company took the decision, starting in
December, to maintain rationing during the dry season and increase –as has been pinted
out—the underground water supply by digging tour additional wells, which began
functioning next year in February and March.
Comparison of demand and expected supply for the dry season months is illustrated
in Figure 5.
Milliones of liters per day
Figure 5. Comparison of water demand and supply
8
6
4
2
0
1
4
7
Demand
10
Supply
13
11
Effect on the financial situation of the water supply entreprise
As a result of the above, the water supply company’s financial situation was affected during
the drought. Although Government decided to maintain the subsidy to the company to face
the emergency, income from billing fell in proportion to demand was actually served,
operational costs of the wells system increased significantly and new investments were
required to increase supply from new wells. All these effect are of an indirect nature,
according to ECLAC’s classification of damage, since it is future flows that are affected.
Account has to be made of the insurance the company had against risks which cobres
75% of direct losses –which was not the case with the drought—as well as a variable
percentage of the increased operation costs or reduced income (excluding the
Government’s subsidy) as follows:
-
For the first six months
During the next six months
During the next three months
After the 16th
100%
67%
33%
0%
12
WORK TO BE DONE IN GROUPS
Work in groups for this exercise will consist on estimating the impacto n the water supply
enterprise as a result of the drought. To solve it use shall be made of the data from the
financial statements indicated, make the appropriate projection of increased expenditure
(both investment and operational) and reduced billing, discounting insurance
reimbursements.
This implies determining the following expenditure ítems
:
-
Investment required for the digging and equipment of the new deep wells and their
connection to the electric grid and the water treatment plant
Los mayores costos de operación del sistema antiguo de pozos al aumentar el
número de horas diarias de funcionamiento
Los costos de operación de los nuevos pozos podrán asumirse como iguales a los
del sistema antiguo
Además, requiere de estimar los menores ingresos derivados de la menor facturación por el
servicio, teniendo en cuenta los volúmenes suministrados en comparación con la demanda
usual a lo largo del período de la sequía.
Posteriormente, se deberá tener en cuenta en estas estimaciones los reembolsos que realice
el seguro una vez que le hayan sido presentadas las cuentas por parte de la empresa.
Deberá también hacerse una estimación acerca de los efectos que los daños arriba descritos
tendrán sobre el sector externo del país afectado. Para ello será preciso calcular los rubros
siguientes:
- El valor o la proporción del costo de equipos y materiales que no son producidos en
el país, y que por lo tanto deberán importarse, y
- La proporción de los reembolsos del seguro que deberá provenir del exterior debido
a las pólizas de reaseguro.
EN
LOS ANEXOS SE PRESENTA LA INFORMACIÓN BÁSICA QUE SE REQUIERE
PARA LA REALIZACIÓN DE LAS ESTIMACIONES ANTES ANOTADAS.
13
ANEXO
DATOS BÁSICOS PARA EL EJERCICIO DE AGUA POTABLE
14
I. Costos unitarios de inversión
Perforación y entubamiento de un pozo en un diámetro de
200 milímetros, con profundidad total de 50 metros,
Por metro lineal
Equipo sumergible de bombeo con capacidad de 6 litros por
Segundo y carga dinámica total de 40 metros, cada uno
Motor eléctrico de 12 HP y equipos eléctricos auxiliares con
Acometida de 45 KVA, cada uno
Caseta para albergar todo lo anterior, cada una
US$
250
US$ 7,500
US$ 5,000
US$ 1,800
II. Costos de operación
Costo mensual de operación de cada pozo, funcionando a
Razón de 10 horas diarias
US$ 215
Costo mensual del operario de los pozos, pudiendo atender
Entre 2 a 3 unidades
US$ 300
Nota: Al aumentarse el número de horas diarias de operación de los pozos, habrá que
asumir un aumento proporcional en los costos arriba anotados.
15
III. Ingresos de operación
Ingreso promedio mensual por facturación, correspondiente a
Un volumen de 6 millones de litros por día
US$ 18,885
La demanda y el suministro previstos a lo largo del período de la sequía se muestra en el
siguiente cuadro (cifras expresadas en millones de litros por mes):
Mes
1
2
3
4
5
6
7
8
9
10
11
12
13
Demanda
6.4
6.7
6.9
6.5
6.2
6.0
5.6
5.3
5.1
5.5
5.8
6.0
6.4
Suministro
3.3
5.1
4.7
5.0
4.0
3.5
3.9
3.9
4.1
4.7
4.2
4.7
6.4
IV. MONTO DEL REASEGURO EN EL EXTERIOR
La empresa aseguradora local estaba reasegurada en el exterior con un consorcio europeo.
El monto del reaseguro equivale al 70% del valor de los daños que sea reembolsado por la
aseguradora local.
16
ESTIMACIÓN DEL RESULTADO DEL EJERCICIO DE AGUA POTABLE
CONFIDENCIAL
ESTE DOCUMENTO NO DEBE SER ENTREGADO A LOS PARTICIPANTES
17
Hoja de Cálculo
Inversión requerida
Cuatro (4) pozos profundos de 50 metros, US$ 250/metro
Cuatro (4) bombas sumergibles, 6 l/s, 40 m TDH
Cuatro (4) equipos eléctricos, 12 HP, 45 KVA
Cuatro (4) casetas
US$ 50,000
30,000
Total
Mayores costos mensuales de operación
Cinco pozos antiguos operando 15 horas por día
Dos operadores de pozos cobrando sobresueldo
20,000
7,200
US$107,200
US$ 537.50
300.00
Dos nuevos pozos operando 15 horas diarias
Un operador cobrando sobresueldo
US$ 645.00
450.00
Meses del 1 al 12
MAYOR COSTO DE OPERACIÓN DE LOS POZOS ANTIGUOS, US$ 837.50/MES
US$ 10,050
Meses del 9 al 12
DOS NUEVOS POZOS A RAZÓN DE US$ 1,095/MES
4,380
Meses del 10 al 12
Dos nuevos pozos a razón de US$ 1,095/mes
US$
US$ 3,285
Total
US$ 17,715
18
Menores ingresos de operación
Mes
1
2
3
4
5
6
7
8
9
10
11
12
Totales
Millones de litros por día
Demanda
Suministro
6.4
3.3
6.7
5.1
6.9
4.7
6.5
5.0
6.2
4.0
6.0
3.5
5.6
3.9
5.3
3.9
5.1
4.1
5.5
4.7
5.8
4.2
6.0
4.7
Déficit
3.1
1.6
2.2
1.5
2.2
2.5
1.7
1.4
1.0
0.8
1.6
1.3
Déficit,
US $
9,757
5,036
6,924
4,721
6,924
7,869
5,351
4,406
3,147
2,518
5,036
4,092
65,781
Menores gastos de operación (planta potabilizadora)
Por una relación entre el agua servida durante el año en comparación con la que habría
debido servirse bajo circunstancias normales, es posible estimar que la reducción en
potabilización del agua es del 29.4%. Combinando dicho porcentaje con el costo anual
respectivo (US$ 2,125/mes) se estima un menor costo de operación en la planta
potabilizadora de US$ 7,489 en los doce meses de la situación de emergencia.
Estimación reembolso del seguro
Primeros 6 meses
Déficit operacional
Reembolso 100%
US$ 41,231
US$ 41,231
Segundos 6 meses
Déficit Operacional
Reembolso 67%
US$ 24,550
US$ 16,449
Total reembolso 12 meses
US$ 57,680
19
Resumen de los daños indirectos
Inversión en nuevo sistema de pozos
Mayores gastos de operación
Menores ingresos por facturación
US$ 107,200
17,715
65,781
Daños totales US$ 190,696
Menos: rembolso del seguro
Menos: menores gastos de potabilización
Daño neto total
Efectos sobre el sector externo
Importaciones
Costo sistema nuevo de pozos (50%)
Costo equipos de bombeo (90%)
Costo equipos eléctricos (90%)
Casetas (15%)
Proporción energía importada para bombeo
US$ 25,000
27,000
18,000
1,080
...
US$ 71,080
Total
Ingreso de divisas
Reaseguro (70% del reembolso del seguro local)
(57,680)
(7,489)
US$ 125,527
US$ 40,376
Balance
(US$ 30,074)