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Vol. 65 · No. 3 · 291–3032011

DOI: 10.3112/erdkunde.2011.03.06 http://www.erdkunde.uni-bonn.deISSN 0014-0015

METEOROLOGICAL PATTERNS AND FOG WATER COLLECTION IN MOROCCO

AND THE CANARY ISLANDS

Mª V ictoria M arzol, José luis s ánchez and aMalia Y anes

With 8 gures, 4 tables and 4 photos

Received 28. October 2010 · Accepted 06. July 2011

Summary: The aim of this study is to characterize the synoptic weather patterns that justify fog water collection on thecoast of Morocco and the Canary Islands. In spite of the fact that they are only 200 km apart and are both affected by thesame stratocumulus cloud formation, the latter behaves differently. Furthermore, fog water collection is studied to evalu -ate its feasibility as a sustainable water resource to satisfy the drinking water needs of a rural population in SW Morocco. The study period was from 2006 to 2010. Standard Fog Collectors ( SFC ) and the Quarter Fog Collectors ( QFC ) that wereconnected to automatic meteorological stations with which hourly and daily data can be recorded were used. The averagequantities of collected water were about 10 l/m 2/day at both sites, but there is inverse seasonality since more fog water iscollected in Morocco in the winter whereas in the Canary Islands this happens in the summer.

Zusammenfassung: as iel dieses rtikels ist, die synoptischen Wettermuster zu beschreiben, die die ebelwassergewin�as iel dieses rtikels ist, die synoptischen Wettermuster zu beschreiben, die die ebelwassergewin-nung an der Küste Marokkos und auf den Kanarischen Inseln rechtfertigen. Obwohl diese Gebiete nur 200 km voneinanderentfernt sind und beide von den selben Stratokumulus Wolkenformationen beeinusst werden, verhält sich das letztere an-ders. ußerdem wird die ebelwassergewinnung bewertet, um ihre urchführbarkeit als dauerhafte Trinkwasserquelle fürdie ländliche Bevölkerung im Südwesten Marokkos festzustellen. er eitabschnitt des Studiums geht von 2006 bis 2010.ie usstattung, die verwendet wurde, sind die Standard Fog Collectors ( SFC ) und Quarter Fog Collectors ( QFC ), d.h.ebelwassersammler mit normalem und Einviertel Leistungsvermögen, die mit automatischen Wetterstationen verbunden werden, mit welchen stündliche und tägliche aten aufgenommen werden können. er urchschnitt an Wasseraufnahmebetrug ungefähr 10 l/m2/Tag in beiden Gebieten, jedoch ist der Saisoneffekt umgekehrt, denn es wird in Marokko mehrebelwasser im Winter gewonnen, während dieses auf den Kanarischen Inseln im Sommer geschieht.

Keywords: Fog water, rural communities, synoptic weather patterns, Morocco, Canary Islands

1 Introduction

Stratocumulus cloud formation is commonin both the Canary Islands (Spain) and along the tlantic coast of Morocco, where it is referred to lo-cally as mar de nubes (sea of cloud) and tagut respec-tively. In both cases, they are advective clouds whichacquire the orographic features of the area becauseof the relief effect and turn into advection fog andmountain fog, ( sharon 1980; cereceda et al. 2002;BruiJnzeel et al. 2005; W alMsleY and scheMenauer

1996; eugster 2008; Foster 2010); and it is possibleto collect part of their liquid content using articialsystems (Photo 1). The water collected for this way can be used by the people living in areas of watershortages for domestic consumption, as in the caseof Morocco, or to maintain ecosystems, as in the caseof the Madeira or Canary Islands ( scheMenauer andcereceda 1991; cereceda and scheMenauer 1996;

hutleY et al 1997; d aWson 1998; P ascon 1979;conac 1985; oliVier 2002; M arzol 2008; M arzol et al. 2010; V illegas et al. 2008; Prada et al. 2009).

The source of this cloud formation is connected with the zores anti�cyclone, subsistence thermal in- version and the cold Canary Current, ( dorta 1993;M arzol 2005). It is of interest, therefore, to know the development processes of the air pressure (lo-calization, frequency and intensity) in the lower lay -ers of the atmosphere in this part of the tlantic, asthis would explain the occurrence of this efcient

natural resource.Since June 2006, the University of La Laguna

has been collaborating with the Si Hmad erhamFoundation (Casablanca, Morocco) on a study aboutthe viability of providing drinking water to rural com-munities in the area around Mount Boutmezguida,in the ït Maâmrane region of Morocco: This regionis 30 km from the tlantic coast in SW Morocco.

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The population is made up of twenty communities – 1,550 people and 5,000 animals – which have serioussurvival problems. On the one hand, the shortage of drinking water complicates not only their domestictasks, but also their farming and livestock activities;and on the other hand their lands are physically iso-lated from the rest of the country by the nti�tlas

Mountains. The scarce economic resources of the re-gion, coupled with a hostile environment (droughts,poor quality soils, small harvests, lack of water, deg -radation of the vegetation cover due to the absenceof appropriate livestock management, poverty, etc.),have led to a high level of voluntary male emigrationto the nearest towns in search of construction work and to illegal emigration to Spain (Photo 2).

These circumstances have meant that womenhave become the sole economic agents as they are theonly ones left to perform the hard, physical work onthe land in this difcult rural setting ( Mernissi 2000;driss Ben 2004; Ben a ttou 2006). This makes them

more vulnerable due to the disproportional respon-sibility they now have for completing the domestictasks and for looking after the family group. They perform the physically demanding task of fetching the daily water requirements, making round trips of 3 to 4 hours which involve carrying large weights of water back to their homes. Fetching water takes timeaway from their farming and domestic activities and,even, from their own education and training. Thistask also consumes more than a third of the energy

produced by their daily food intake ( l aBorde andMorel 1991; lide 1995; P arish and Funnel 1996; t azi s adeq 2007; oFouéMé-Berton 2010).

The ultimate objective of this research project isto provide water to the local population. Large Fog

Collectors ( LFC ) will be built to collect fog water inorder to do this. The Si Hmad erham Foundationhas conducted several population surveys and ananimal census to quantify the real water needs in theregion. Some of the most relevant ndings are asfollows: – Women are responsible for getting the water re-

quired for drinking, domestic purposes and perso-nal hygiene. They fetch the water from wells at thebottom of the oueds . This job is not done by anyoneunder the age of 16 because of the danger involvedat the access to the wells. – Women are forced to cover more than 1.5 km oneach trip, two in the winter and six in the summer. – The average time taken for the journey to the oueds ranges between 90 minutes and two hours, withthe added difculty of crossing steep slopes as thearea is mountainous. They have to carry a load of two bramels (30 l plastic water containers).

– Most families do not have tanks to store the wateror treat the water to make it suitable for drinking. s a result, the people, especially the children,are exposed to health problems caused by unsafe water. – The average daily consumption per family, in win-

ter, is 30 litres for drinking and cooking, and about200 litres for personal hygiene and consumptionby the animals. These amounts double in the sum-mer because the animals, mostly goats, need more water every day.

Photo 1: Image from 24th April 2000 showing how the cloudsreach the Canary Islands and the Atlantic coast of Morocco.Source: SeaWiFS Project, NASA

Photo 2: The communes near Mount Boutmezguida experi-ence the effects of erosion, lack of water and poor qualitysoils (© Marzol)



293 M. V. Marzol et al.: Meteorological patterns and fog water collection in Morocco and the Canary Islands 2011

– The communities in Tamenrout, gni, ’ekri, with a total population of 154 adults, and theMedersa Sidi ekri with 35 schoolchildren, werechosen for the installation of the LFCs becausethey have the greatest difculties regarding water

availability. The possibility of providing drinking water to thesecommunities via the LFCs means, without doubt, animprovement in their quality of life and an impor-tant collaboration in the sustainable development of a rural population who, because due to the great dif -culties they face in their communities, are opting to leave the countryside and their roots to emigrateto the towns.

The work done so far has been to evaluate theamount of potential water that could be collectedand to study its annual variations, as this resource isirregular in terms of time. The research project hasalso studied the relationship between the fog watercollected and wind speed and direction, as these areessential meteorological variables on which the wa-ter collection of the screens depends. standard fog collector ( SFC ) ( scheMenauer and cereceda 1994a) was used in the rst phase of the study and the read -ings were made by local people; later on, a quartersize fog collector ( QFC ) was installed with the samemesh as the SFC. This QFC is connected to an au-tomatic meteorological station that supplies hourly information on all the variables and makes it possi-ble to decide on the most favourable environmental

conditions for the greatest collection of water (seePhoto 3). The QFC is a screen of 50 x 50 cm designed

in 2002 in order to facilitate the construction andinstallation on site ( M arzol 2002, 2005).

s well as collecting the fog water for human use,the frequency of fog also plays a role in maintaining vegetation, which in the Canaries and on the orth

frican coast is of great botanical value. long withthe zores, Madeira and Cape Verde Islands, theseparts of the world are home to ancient ora that, witha large number of endemic species, ourished in theMacaronesia and in the fro�European continentalterritory during the Tertiary period, e.g., Aeonium aboreum, Dracanea draco, Euphorbia regis jubae, Echium plantagineum, Rumex vesicarius, Erica arborea, Myrica faya,Laurus azorica, Argania spinosa, Acacia gummifera, etc.( Peltier 1978; Médail and quézel 1999; r oMane 2000; g arcía-s antos 2007; r iVas M artínez 2009;M arzol et al 2010; ohsaWa et al. 2010). The needto ensure the survival of this natural vegetation, which is of great oristic richness, led the Moroccanand Spanish authorities to set out different levels of botanical protection in these areas by means of thedeclaration of Rural Parks in the case of the Canary Islands ( M artín et al. 1995) and Important onesfor Plants ( IP ) in Morocco.

2 Study area, data and methods

Special emphasis in this research work was givento investigating the similarities and/or differences in

the behaviour of fog in Morocco and the Canaries, which are 200 km apart. Two experimental sites

Photo 3: The equipment used in the stations at Boutmezguida is a SFC and a QFC (photo on the left) and Anaga there are twoQFCs with different meshes (photo on the right). In both cases the meshes are connected to meteorological stations (© Marzol)



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were chosen in order to do this: The rst site is inBoutmezguida in SW Morocco, 1,225 m a.s.l. 30 kmfrom the tlantic coast (29 º12’30’’ – 10º01’30’’W);the second site is in naga in the NW of the islandof Tenerife, 842 m a.s.l. and 4 km from the coast

(28º32’09’’ – 16º14’11’’W) (Fig. 1).

The selected site in Morocco has a semi�arid,dry climate with strong daily and yearly thermalcontrasts, associated with high annual and inter�annual variability and torrential rain, although an-nual averages are not above 150 mm. The vegetationis dominated by large areas of mountain argan trees

( Argania spinosa ), alternating with land mainly culti- vated with cereals as the soil is poor and there is littlerain ( ezaidi and ait tirri 2002). The site chosen inthe Canary Islands has a damp temperate climate, with about 550 mm of rainfall a year. Its natural

vegetation consists of green mountain plants with a

predominance of Myrica faya and Erica arborea , whichblend in with vegetable plants, fruit trees and vinescultivated for reasons of self�sufciency ( M arzol 2008) (Photo 4).

The study on fog water collection inBoutmezguida began in June, 2006 with the instal-

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Fig. 1: The location of the study sites in the Canaries and Morocco, which are 4 km and 30 km from the ocean, respectively

Photo 4: The Anaga station is well positioned (indicated by the circle) to benet from the clouds coming from the Atlantic which are channelled by the relief (© Marzol)




lation of two SFCs orientated towards WNW (300°)and NNW (340°), because, in the opinion of the lo-cal population, these are the most common winddirections ( M arzol et al. 2007, 2008). The rst of these SFCs was substituted, in September 2009, by a

QFC connected to a meteorological station and ori-entated towards NNW as it was the most efcientdirection according to three years of analysis. TheSFC directed towards the NNW was kept in placein order to correlate the two sizes of collector. Theautomatic meteorological station used, the avismodel, records information concerning temperature,humidity, pressure, wind speed and direct ion and theamounts of water collected by the QFC on an hourly basis (see Photo 3).

The analysis of the fog water collection in nagabegan in 1996. t the present time, two QFCs con-nected to the SEC model automatic meteorologicalstation (Spanish Society for Cybernetic pplications)are being used. The station records information eve-ry ten minutes on all meteorological variables andthe fog water collected by the screens. The altitudeand the good topographic conditions mean thathigh daily average quantities of water are collected( M arzol and V alladares 1998) and the quality of the information, over 14 years of continuous data, isproof that this station is a good example for charac-terizing the fog on the island and for comparing it with other places.

The amounts of water collected by the SFC were

too high for the tipping bucket of the automaticmeteorological station to function accurately and asmaller sized screen was necessary. Therefore, simul-taneous experiments were conducted in both sites with two different sized screens, 1 m2 ( SFC ) and ¼m2 ( QFC ), to study the water collection in both sites. The results revealed that the QFC in Boutmezguidacollected 8% less water than the SFC per m2 andthe opposite is true in naga where the QFC col-lected 13% more water than the SFC per m2. A cor-rection factor of 1.086 was applied to the data fromBoutmezguida ( SFC (l/m 2 ) = QFC (l/m 2 ) x 1.086 ) anda correction factor of 3.5 was applied to the data

from naga. For example, in February 2011, theSFC installed in Boutmezguida collected 158.6 l/m2 of fog water whereas the QFC, 15 metres away, col-lected 146.1 l/m2; these quantit ies show that the SFCcollects 7.9% more than the QFC.

Two approaches were used to evaluate the fog water collection in the study area: The rst was todene the features of the fog in the SW of Moroccoand to reveal its differences to the fog of the Canary Islands. The second approach was to locate, from

a geographical point of view, the pressure centreson the days when there was fog in Boutmezguida,(Morocco). This was carried out from 12 June 2006, when the study began, to 30 September 2010. Thenal step was to decide whether there is a pattern

of the meteorological and atmospheric conditions inthe Sahara and the tlantic that explain the seasonaldifference in fog water collection between Moroccoand the Canaries.

The correlation study of the wind and water usesan hourly scale. The basic problem with the analy -sis of fog water collection is when occur at the sametime as the rain ( M arzol 2008). In order to elimi-nate this over�evaluation, a decision was made todistinguish the total amount of water collected by the screens (fog plus rain) from that coming only from fog, whereby the days with rain were removedfrom the computation. Furthermore, the automaticmeteorological station in naga supplies hourly dataon the collection of water that only comes from fog. This information is valuable because the screens col-lect water from fog during many hours when it israiny, and these hours can be computed.

The methodology used in the synoptic analysisof the days with fog in Morocco is based on dividing the tlantic space into 80 squares of 5º longitude by 5º latitude delimited between 40ºW and 20ºE longi-tude and between 25º and 70º latitude (Fig. 2). This method was used to geo�reference the type of pressure centre – anticyclone or depression – and its

pressure ( dorta et al. 1993). The information wastaken from the synoptic maps at 12.00 hours GMT from the EMET (Spanish ational Meteorological gency). Finally, the synoptic data, meteorological

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Fig. 2: Template for extracting information from the geo-graphic location of pressure centres on days with fog inMorocco



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variables and water collected by the SFCs and QFCsin Boutmezguida and naga were used to create adata base.

3 Results

3.1 Cloud frequency in the SW of Morocco andthe Canary Islands

In Morocco, there was fog on only 33% of thedays (552) out of the total of 1,570 days during theanalysis (12 June 2006 to 30 September 2010). There was also fog in naga on 89% or 464 of those days. There was rain in Boutmezguida on 66 days andon 145 days in naga of the 552 days with fog inMorocco. The “interference” caused by the waterfrom the rain in calculating the collection of waterfrom the screens only amounts to 4% of the totalnumber of analysed days in Morocco and 9% inthe Canaries, affecting, above all, the period fromOctober to March. There were 1,239 days with fog in the Canaries (83% of the total) during the study period.

The difference between Morocco and theCanaries does not mean there is less cloud over theislands, but rather that meteorological events do notoccur simultaneously in both places. The greaternumber of days with rain in naga, which is 17%of the days in the year, can be added to this rst dif -

ferentiating feature. This fact means that methodsof temporal discrimination must be applied to theanalysis of the rates of the fog water collection. Inspite of the higher frequency of fog in the Canaries,the correlation between the amount of water collect-ed and the monthly number of days with fog is lowerthan in Morocco (Fig 3).

3.2 The volumes of water collected

The averages of water collected in both placesare around 10 litres/m2 per day, although there areimportant monthly variations. Table 1 shows the

quantity of water collected by the screens: (F1 ) is themonthly mean of total water collected (fog + rain),(F

2 ) the monthly mean of fog water after eliminating

the water of days with rain, (F3 ) the monthly mean of

fog water after eliminating hours with rain, (1 ) the

daily mean of total water (fog + rain), (2 ) the daily

mean for fog water only, and (3 ) the daily mean

of fog water only, but collected on an hourly basis. ll daily averages for the month include every day of the month. In the case of naga, the differencein the daily collection and the hourly collection of fog water is important (columns 9 and 10 of table 1). When working on an hourly basis, many hours of water are “recovered” as it does not necessarily rainfor 24 hours every fog day.

The most outstanding feature between the twosites is the existence of two seasonal patterns in thebehaviour of the monthly fog water collected (Fig. 4). The daily averages of gure 4 refer to water coming only from fog, these quantities would be higher if thetotal of the water collected by the screens was takeninto account (see Tab. 1). The pattern in Morocco ischaracterized by an average of 11.8 l/m2/day in theseven months from ecember to June; this amountdecreases to 4.3 l/m2/day from July to November

(the values would be 14.5 l/m2

/day and 5.1 l/m2

/day,respectively, if the total of the water collected by thescreens was included in the computation). On theother hand, the pattern of the Canaries is denedby the predominance of vertical cloud developmentduring the winter months and, therefore, there is areduced presence of stratocumulus cloud formationthat in turn lowers the amount of water collected

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y=31.25x - 474.82 R2= 0.3783

Fig. 3: The relationship between the total amount of water collected and number days with fog per month in Boutmezguidaand Anaga (June 2006 to September 2010)




by the screens so that an average of only 3.4 l/m2/day can be guaranteed from September to May, asopposed to 17.3 l/m2/day from June to ugust (the values would be 7.5 l/m2/day and 19.1 l/m2/day re-spectively if the total of the water collected by thescreens was included in the computation). The quan-tity of water collected in the summer is important inecological terms for the islands, because it provideshumidity and water to forest ecosystems when waterstress is at its highest ( M arzol 2005).

Having meteorological stations connected to the

screens available gives one the possibility to study the maximum values of water coming only from fog in different time periods. Thus, in Boutmezguidathere are 1060.0 l/m2/month (March 2009), 115.9l/m2/day (02/07/2010) and 6.7 l/m2/hour (6 hourson 02/07/2010), whereas the quantities in nagaare 1094.0 l/m2/month (July 2007), 81.4 l/m2/day (02/08/2006) and 9.8 l/m2/ hour (16 hours on24/07/2007).

3.3 The synoptic weather patterns in the collec-tion of water

There was a surface anticyclone in the eastern tlantic on 88% of the days with fog in Morocco;on 77% of these days, the centre of the anticyclone was located to the south of the 45º parallel and itsaverage pressure was 1028 hPa. nother anticyclone, whose frequency was very low (4% of the days withfog) and had a pressure of 1019 hPa, was present inNW frica. s far as the low pressure centres are

concerned, there was one over the Sahara on 48% of the days with fog, with an average pressure of 1007hPa (Fig. 5).

The fog water collected in July and ugust inBoutmezguida was only 3.9% of the annual totalcompared to 40% in naga. This water was collectedon 7% of the days in these months in Morocco andon 98% of these days in the Canaries. Both placesalso differed in the daily averages of water collected

Month Boutmezguida (Morocco) Anaga (Canary Islands)

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J 419 277 13.5 8.9 189 35 140 6.1 1.1 4.5

F 364 208 13.0 7.4 207 72 146 7.4 2.6 5.2

M 424 333 13.7 10.7 260 102 194 8.4 3.3 6.3

A 389 389 13.0 13.0 282 162 256 9.4 5.4 8.5

M 410 393 13.2 12.7 288 228 264 9.3 7.4 8.5

J 616 584 20.5 19.5 393 339 388 13.1 11.3 12.9

J 95 48 3.1 1.5 727 694 725 23.4 22.4 23.4

A 561 60 2.0 1.9 641 569 626 20.7 18.3 20.2

S 139 139 4.6 4.6 187 153 179 6.2 5.1 6.0

O 218 160 7.0 5.2 235 113 201 7.6 3.6 6.5

N 270 250 9.0 8.3 174 43 99 5.8 1.4 3.3

D 449 325 14.5 10.5 222 32 141 7.1 1.0 4.6

Mean 3853 3163 10.6 8.7 3803 2541 3361 10.4 6.9 9.2

Tab. 1: Monthly (F1,2,3) and daily (D1,2 ,3) mean amounts of fog water in Boutmezguida (Morocco) and Anaga (CanaryIslands) from June 2006 to September 2010 (l/m2). The daily averages include all the days of the month

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Fig. 4: Mean daily quantities of fog water collected per month in Boutmezguida (Morocco) and Anaga (Canary Islands)from June 2006 to September 2010



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from the fog, since the daily volume was 1.7 l/m2 inBoutmezguida and 22.1 l/m2 in naga.

The daily synoptic maps of July and ugustfrom 2006 to 2010 were analysed in order to ndthe reason for the abovementioned difference. Theexplanation suggested for the differences that ex-ist between Morocco and the Canaries is based ona change in the regional pressure elds during thesemonths, which hinders the fog water collection. Themost outstanding features of this change are: – A lower frequency of the Atlantic anticyclone

(85% of days in July and ugust) but a closer pro-ximity of its centre to the Canaries. The averagepressure is slightly lower than that of the rest of

the year, which is 1027 hPa (Fig. 5). – greater frequency of the thermal depressionover the East of the Sahara (73% of days in July and ugust) which, with an average pressure of 1008 hPa, reduces its area of inuence to the Southof the tlas Mountains. – The appearance of a surface anticyclone of 1015

hPa over the tlas Mountains on 42% of the daysin July and ugust.

The three pressure centres create a strong barometri-cal gradient in both months, which give rise to mod-erate E trade winds parallel to the Moroccan coast-line or from the tlas Mountains towards the coast. These winds prevent tlantic cloud from penetrating into Moroccan territory, but favour their path overthe Canary archipelago (Fig. 5). The 3 July 2007 ex-emplies the atmospheric situation during these twomonths. The amount of water that was collected only from the fog in naga was 99.7 l/m2, but nonethe-less it was a warm, sunny day in Boutmezguida. Thesurface maps shows how the tlantic high, in con-

junction with the thermal depression over the Saharaand a smaller anticyclone in the orth of lgeria,sent hot, dry air towards the frican tlantic coast. This focus of heat above the desert, which is a fog inhibitor, stayed in place up to 1,500 m a.s.l., as canbe seen in the image at 850 hPa from the reanalysisof this day (Fig. 6).

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Fig. 5: The location of the pressure centres in the North Atlantic on days with fog and on days without fog (July and August)in Morocco from 2006 to 2010

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Reykjavik03JUL2007 00Z 850 hPa Temperature (°C)

Data: Reanalysis of NCEP. © Wetterzentrale (www.wetterzentrale.de)

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1 0 0 8

1 0 1 6

1 0 1 6

1 0 1 6

1 0 1 6

1 0 1 6

1 0 1 6

1 0 1 6

1 0 1 2

1012

1012

1 0 0 8

1 0 0

0

9 9 6

1 0 0 4

1 0 1 2 m b

1 0 1 2 m b

1 0 0 8

1 0 0 8

1 0 0 8

1 0 0 8

1 0 0 8

1 0 0

0

9 9 6

9 9 2

9 9 2

1 0 0 4

102 0

10 2 4

102 8

102 0

10 2 4

102 8

100

0

-5

10

10

15

15

15

15

15

55

10

10

20

25

20

2530

0

30

20

10

0

-10

-20

-30

Fig. 6: Surface map and reanalysis map at 850 hPa from 3rd July 2007, an example of a day with fog in Anaga and without fogin Boutmezguida (© AEMET y Wetterzentrale)




evertheless, on 12 pril 2007 when 20 l/m 2 werecollected in Boutmezguida and nothing in naga,the atmospheric situation that existed there was of pressure centres in the region of the Canaries andNW frica that, together with the orth winds, fa-

cilitated the entry of the cloud across the Moroccancoastline; at the same time, the quantity of the fog water collection increased in Boutmezguida, but de-clined in naga (Fig. 7).

4 Discussion

The results obtained here support the viability

of collecting a part of the liquid content of clouds,as an average of 10 l/m2/day are assured in bothsites, although there are large monthly contrasts.Even though the total amount of water collected isthe same, the efciency of phenomenon is greater inBoutmezguida because the water there can be col-lected, on average, on ten days a month as opposedto needing twenty�four days in naga.

These water averages are higher than those ob-tained in other areas in South merica (Cerro Orara,Peru; La Ventosa in Guatamala; Puluahua, Equador;El Tofo, Chile) and in frica (Woodbush, South frica), which several authors consider to be optimal

( scheMenauer and cereceda 1994b; cereceda andscheMenauer 1996; oliVier and r autenBach 2007;M arzol and s ánchez 2008).

The differences found between Morocco andthe Canaries leads one to think that there are twopatterns of fog behaviour in the region of the Canary Islands and NW frica. On the one hand, there isthe Moroccan Pattern where the largest amounts of water are collected from ecember to June, with anaverage of 14.5 l/m2/day, but is lower in the months

of July and ugust (5.1 l/m2/day); and on the otherhand, there is the Canary Pattern with a marked ef-ciency in July and ugust, with an average daily col-lection of 19.1 l/m2, which is not the case for the restof the year when the average is 7.5 l/m2/day.

The explanation for these differences lies in thedisappearance of necessary atmospheric conditionsfor collecting water – high humidity, low tempera-tures and a suitable wind speed – in the Sahara esert

during of summer (table 2 shows the differencesbetween January and ugust 2010). t this time of year, the heat and drought coupled with weak E

and E winds prevent the tlantic cloud formationsfrom moving onto the continent. Figure 8 shows thedominating wind direction in a dry month, ugust,and in another month with numerous fog events,such as January 2010, when 350 l/m2 of water werecollected. The predominating continental wind wasfrom the E in ugust, whereas the wind oscillatedbetween NNW and E in January 2010, which fa-cilitated the arrival of the damp ocean air. At thesame time, there are also differences between thehours with collection of fog water and the dry hoursin January.

Wind speed is another conditioning factor of

water collection. Certain studies report that the bestspeed is between 3 and 6 m/s, and the correlation de-clines with higher and lower speeds ( scheMenauer etal. 1988; scheMenauer and Joe 1989; scheMenauer and cereceda 1993a,b, 1994c; V illegas et al. 2008). The available data show that the greatest water col-lection in Boutmezguida occurs with slightly higher wind speeds: from 6 to 8 m/s. Table 3 shows that 40%of the fog water in January 2010 was collected withinthe abovementioned wind speed range. nother ex-

60°

50° 40°

50°

60°

30°

60°

50° 40°

40°

30° 20°

40°

50°

60°

30°

30°

20°

30° 20°

30° 20°

10°10°

10°10°

0°

0°

Paris

Bern

Vienna

Budapest

Warsaw

Copen-hagen

OsloStockholm

Helsinki

Rome

MadridLisbon

Rabat

Algiers

Tunis

Brussels

The Hague

Berlin

London

Dublin

Reykjavik12APR2007 00Z 850 hPa Temperature (°C)

Data: Reanalysis of NCEP. © Wetterzentrale (www.wetterzentrale.de)

30

20

10

0

-10

-20

-30

0 5

5

5

20

15

9 8 8 9 9 2

9 9 6

1000mb

9 8 4

9 8 8 9 9 2

9 9 6

1 0 2 4

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1 0 1 6

1 0 0 0

1 0 0 4 1

0 0 8

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1 0 2 0 m

b

1 0 2 0 m

b

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1 0 2 4

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8

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-15

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-10

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-10

-10

0

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-5

H

H

L

L

L

1 0 1 6

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1 0 1 2

1 0 0

8

1000mb

9 8 4

1 0 0 0

1 0 0 4 1

0 0 8

1 0 1 2

-5

-5

Fig. 7: Surface map and reanalysis map at 850 hPa from 12th April 2007, an example of a day with fog in Boutmezguida and without fog in Anaga (© AEMET y Wetterzentrale)



300 Vol. 65· No. 3

Tab. 2: Data taken from the automatic weather station in Boutmezguida in the periods (hours) with and without fog in January and August 2010

January 2010 August 2010

Total number of hours with data 675 hours 744 hoursHours with fog 287 h (42%) 23 h (3%)

Hours without fog 388 h (57%) 721 h (97%)Mean wind speed in hours with fog 6.3 m/s 5.8 m/sMean wind speed in hours without fog 2.4 m/s 3.9 m/sHumidity in hours with fog 97% 92%

Humidity in hours without fog 69% 29%

Mean temperature in hours with fog 7.9ºC 14.3ºCMean temperature in hours without fog 11.0ºC 29.3ºC Total amount of fog water collected 350.1 l/m2 23.6 l/m2

Hourly maximum7.1 l/m2/h (07 h, E, with

9.8 m/s)2.5 l/m2/h (06 h, W,

with 6.3 m/s)

NNNE

NE

ENE

E

ESE

SE

SSES

SSW

SW

WSW

W

WNW

NW

NNW

Boutmezguida

August 2010

10.1 - 12.0

8.1 - 10.0

6.0 - 8.0

2.0 - 5.9

0.6 - 1.9

NNNE

NE

ENE

E

ESE

SE

SSES

SSW

SW

WSW

W

WNW

NW

NNW

January 2010(hours with fog water)

Calms (<0,6 m/s): 3,5%

Calms (<0,6 m/s): 0.3%

NNNE

NE

ENE

E

ESE

SE

SSES

SSW

SW

WSW

W

WNW

NW

NNW

January 2010(hours without fog water)

Calms (<0,6 m/s): 7.8%

m/s

30%20

0

30%20

10 0

30%20

10

30%20

10 0

30%20

10 0

0

30%20

10 0

Fig. 8: Wind roses from August 2010 (month without fog water) and January (month with fog water) in Boutmezguida, Mo-rocco. Wind roses for January show the differences between the hours when fog water was collected and the hours withoutfog water




ample conrming the importance of the wind speedin the collection of water and in dening the twopatterns can be found by looking at what happenedin the wet month of January 2010, when 57% of thehours were predominated by NNW and E windsand 70% of the water was collected when the windscame from these directions (Tab. 4).

5 Conclusion

The comparison of the fog characteristics onthe tlantic coast of Morocco and in the Canary rchipelago reveals the existence of two specic pat-terns. These two patterns are a response to the dif -fering organization of pressure elds in the tlanticand orth frican region. Therefore:

– In the Moroccan pattern , large amounts of watercan be collected during the seven months of theyear between ecember and June, as for example, when nearly 15 l/m2/day of water can be collectedon average, whereas the water collection is three

times lower in the summer. – The Canary pattern behaves inversely to theMoroccan model and is highly efcient from Juneto ugust when the average quantity of water coll-ected is 19 l/m2/day, but this average is three t imeslower during the rest of the year.

The explanation for this difference lies in the changeof the atmospheric conditions, basically wind direc-tion, in the summer in the east of Morocco. The dry winds from the Sahara impede the tlantic cloudsfrom entering the continent.

The average amounts of water collected from fog conrm the viability of collecting it in SW Moroccoand a favourable diagnosis can be made for using this collection system. The access problems of the lo-cal population to water, where consumption is below the minimum level laid down by the WHO (2003)and UESCO (2006), means that this system is asustainable and suitable solution for use in dispersedrural communities, as it will provide these commu-nities with meaningful social, economic and healthbenets, especially for the women and children.

The resource of fog water is assured on one outof every three days a year, it is abundant in the win-ter months, but almost inexistent in July and ugust,

which is why it will be necessary to include this im-portant feature in supply forecasts. Basic domestic water requirements can be met by the installation of LFCs near the communities with the greatest sup-ply problems, and by the provision of water storagetanks as well as by a water treatment programme tomake it drinkable. nother way to take advantage of this method of obtaining water is to put a containerbelow the argan trees to collect the water that contin-uously drips from their branches, which could thenbe put into troughs for the livestock.

Acknowledgements

This study is part of a research project nancedby the irección General de Relaciones con fricadel Gobierno de Canarias. The authors would liketo thank Mustapha Beilla and Mohammed riouchfor collecting the data and for the maintenance of the station in Boutmezguida, and . Corel ( CEM, Valencia) for facilitating the software for the windanalysis.

Tab. 4: Relationship between wind direction and the quan-tity of fog water collected in January 2010 in Boutmezgui-da, Morocco

DirectionNumber of

hours%

Amount of water (l/m2)

%

N 100 15 39,9 11

NNE 187 28 170,2 49

NE 35 5 0,6 0

ENE 14 2 0 0

E 13 2 0 0

ESE 6 1 0 0

SE 6 1 0 0

SSE 2 0 0 0

S 6 1 0 0SSW 51 8 0,8 0

SW 25 4 0,3 0

WSW 36 5 16,2 5

W 16 2 14,5 4

WNW 13 2 14,8 4

NW 32 5 33,1 9

NNW 100 15 59,7 17

CALM 34 15 0 0

Total 674 350.

Tab. 3: The percentage of fog water collected as a functionof wind speed category in Boutmezguida in January 2010

m/s Total of

hours%

Total of water l/m 2 %

< 0.6 34 5 0.6 0.2

0.6 – 1.9 109 16 0.9 0.22.0 – 5.9 285 42 81.7 23.3

6.0 – 8.0 161 24 139.0 39.7

8.1 – 10.0 70 10 96.9 27.7

10.1 – 12.0 17 3 31.1 8.9

Total 676 350.1



302 Vol. 65· No. 3

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Authors

Prof. r. Mª Victoria Marzol

. José Luis Sánchez MegíaProf. r. malia Yanes Luque

epartment of Geography University of La Laguna

38071 La LagunaCanary Islands

Spain

[email protected]@telefonica.net

[email protected]

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