Ministero Affari Esteri ISTITUTO AGRONOMICO PER L’OLTREMARE
LIBIA “ MIGLIORAMENTO E VALORIZZAZIONE DELLA PALMA DA DATTERO NELLE OASI DI AL JUFRA”
Questa pubblicazione è realizzata nell’ambito del programma Miglioramento e valorizzazione della palma da dattero nelle oasi di Al Jufrah in Libia finanziato dalla Direzione Generale per la Cooperazione allo Sviluppo del Ministero Italiano degli Affari Esteri e coordinato dall’Istituto Agronomico per l’Oltremare di Firenze in collaborazione con l’Ente libico per lo sviluppo e il miglioramento della palma da dattero e dell’olivo.
THE GEOGRAPHIC INFORMATION SYSTEM OF DATE PALM PLANTATIONS IN AL JUFRAH REGION
1. INTRODUCTION ....................................................................................................................4 2. THE STUDY AREA .................................................................................................................4 3. METHODOLOGY...................................................................................................................6 3.1 Information sources.............................................................................................................6 3.2 Preliminary phase...............................................................................................................7 3.3 Field survey......................................................................................................................11 3.4 Processing phase ...............................................................................................................12 4. RESULTS ..............................................................................................................................18 4.1 The geographic database....................................................................................................18 4.2 Thematic maps.................................................................................................................20 5. CONCLUSIONS ....................................................................................................................22
1. Introduction The present study has been conducted in the framework of the Italy - Lybia bilateral cooperation project "Improvement and Valorisation of Date Palm in Al Jufrah Oasis", carried out by Istituto Agronomico per l'Oltremare (Italy) and the Board of Improving and Developing Olive and Palm Trees (Tripoli, Libya). With the general objective of supporting and strengthening the date palm production through the improvement and valorisation of production, transformation and commercialisation of local varieties, the project aims to contribute to the social and economic development of the Al Jufra Region. In this framework, the characterisation and description of local varieties, performed through the sampling and description of genetic, morphometric and chemical characteristics, is accompanied by an integrated study of the palm dates cropping system in the Al Jufrah Region. Such study has been carried out by means of the set up of Geographical Information System of Date plantations for the five oasis of Waddan, Hun, Sokna, Zellah and Al Fugha. The work has been carried out in the period January June 2010 at the Geomatics Unit of IAO, with the collaboration of Libyan technicians of the Board of Improving and Developing Olive and Palm Trees. The main goals of the Date Palm Plantations GIS can be summarised as follows: - provide a geographical localisation of plants sampled for varietal characterisation for their follow up in the successive sampling phases; - provide up to date maps of date palms plantations distribution and classification according to their type (cropping system), varietal composition and cultural practices; - provide a complete inventory of present plantations over the whole study area and generate quantitative data about surfaces of presently cultivated areas and of the expansion areas where dates production will start in the next few years; - set up information material representing the actual situation of date palms cropping.
2. The study area The Shabia of Al Jufrah is a broad region extending for about 117000 Km2 between the two mountains of Djebel Waddan et Djebel es-Soda; the northern part of the region is represented by a depression, covering about 2000 Km2 and falling in the elevation range between 200 and 300 m. a.s.l. Here, several smaller depressions cause the raise of water table and the consequent formation of a number of oasis, the three major ones being Waddan, Hun and Sokna; the ancient oasis of Zellah is located in the eastern part of the Shabia, along the traditional pathways connecting the coastal towns with the Sahara, while the oasis of Al Fugha is located south of Djebel es-Soda, at a quite higher elevation, around 500 m. a.s.l.
Figure 1 : The Shabia of Al Jufrah From the geological point of view, most part of the area is composed by sandstone and limestone deposits, but the volcanic activity of Tertiary and Quaternary ages created large basalt deposits in the western and in the south-eastern part of the area. Hard limestone deposits (calcareous crusts) can be often at a shallow depth (often less than 1 m. deep), severely limiting water storage capacity of soils. This is especially true in the oasis of Waddan. The region belongs climatically to the pre-desertic belt; even if a certain influence of the Mediterranean Sea can still be noticed by the relatively abundant winter rains on the surrounding mountains, the rainfall in the lower part of the depression is typically desertic, rarely exceeding 25 mm/year. Temperatures regime shows a great daily excursion, while variations on annual basis are modest. During summer months very high maximum temperatures are often reached. Sandy or very sandy soils are predominant in the Waddan and Hun areas, with a transition towards finer textured soils (sandy loam or loamy soils) in the depression of Sokna. The organic matter is always very low and most soils show a poor to very poor structure, except for heavier soils in the surroundings of Sokna. Soil salinity on irrigated soils, is becoming a more and more widespread threat; in the southern part of Waddan oasis as well as in Hun is common to see thin salt crusts on the soil surface, which is reflected in reduced yield for most crops, included date palms. Depending on the areas, the increase in soil salinity is often caused by poor water quality but an insufficient soil leaching caused by water shortage, is also locally noticed.
3. Methodology The methodological approach followed for the realisation of the GIS is based on a visual interpretation of remote sensing data, successively validated by a field survey for verification of the preliminary interpretation and for data collection, and then finalised by a data processing and map outputs editing phase. Such methodology is detailed in the next paragraphs. 3.1 Information sources Most part of the work for the realisation of the GIS rely on the information extracted from satellite imagery covering the area of interest, as well as on field data collected in situ. Additional data sources have been investigated and integrated as information layers for a more complete description of the area under study. - Satellite data Detection of date palms plantations has been based on the interpretation of various remote sensing products, with different spatial resolutions and acquisition dates, each of them being useful at different stages of the work. The following satellite data have been used for palm plantations detection: Terra ASTER images:
RGB false colour composition, spatial resolution 15 m Acquisition dates: 21/11/2007 for Waddan 09/05/2009 for Hun and Sokna 09/04/2009 for Zellah 03/01/2009 for Al Fugha
SPOT 5 XS images:
RGB false colour composition, spatial resolution 10 m Acquisition dates: 29/07/2009 for Waddan 13/07/2009 for Hun and Sokna
Google Earth Coverage RGB true colour composition, various resolutions depending on zones Acquisition dates: ranging from December 2003 to September 2006, depending on zones - Other data The other information layers of the GIS have been set up through acquisition of the following sources. a) Elevation: Digital Elevation Model (DEM) generated in the framework of the Shuttle Radar Topography Mission (SRTM), with a spatial resolution: 90 m.
The DEM was downloaded from the CGIIAR web site1. Two different tiles (39/07 and 40/07 tiles, respectively) were needed in order to cover the whole Al Jufrah region. Tiles were then submitted to mosaicking and sub-setting (Clipping) according to Al Jufrah administrative boundaries. b) Geology: the reference map used has been the following: A. Desio, "Carta Geologica della Libia". Studio Cartografico G. Giardi, Firenze, Italia. 1938. The map was acquired through scanning and georeferencing, while the legend was translated in english. 3.2 Preliminary phase During this first phase the following series of preparatory activities has been carried out. - Database structure design and implementation The overall structure of the database has been designed through the identification of the main spatial objects (entities) to be represented and the full list of attributes to be stored for date palms classification and characterisation. Plantations are then defined by a polygons layer where each polygon is univocally identified by a progressive numeric code and characterised by a series of attributes. Attributes are stored in four different tables (named "Plantations", "Owners", "Varieties" and "Trees_age") linked between them, giving rise to a relational database according to the scheme shown in figure 2.
Figure 2 : Database structure : relationships between tables 1
Jarvis A., H.I. Reuter, A. Nelson, E. Guevara, 2008, Hole-filled seamless SRTM data V4, International Centre for Tropical Agriculture (CIAT), available from http://srtm.csi.cgiar.org.
Each table stores dates palm attributes that can be referred to the plantation itself, to plantations owners, to the varieties used in the plantation and to their age structure, respectively. Relationships between tables allow easy and clear data consultation and querying. The table below shows the database structure through the list of identified attributes and their characteristics for each table. The fields marked in bold represent the link fields between tables.
TABLE FIELD NAME PL_id PL_sdate PL_oasis OW_id PL_loc PL_psurf PL_perc PL_irr PL_gpsn PL_pcode PL_fcode PL_sel PL_samp OW_id OW_name OW_fcode OW_cold OW_oasis PL_id VR_id VR_nb VR_pr PL_id TR_cl0 TR_cl1 TR_cl2 TR_cl3
FIELD TYPE Id code for plantation Number Date of survey (dd/mm/yyyy) String Oasis name (Waddan, Hun, Sokna, Zellah, Al Fugha) String Owner identification code (999=Unknown, Number 888=Common) Name of locality String Surface of the parcel (ha) Number % of the parcel covered by plantation Number Type of irrigation system (0=absent, 1=Localized, Number 2=Surface, 3=Loc. + Surf., 9=Unknown) Name of recorded GPS point String Preliminary plantation code String Final plantation code String Selected for sampling Boolean Effectively sampled Boolean Owner identification code (999=Unknown) Name of plantation owner String Farm code String Presence/absence of Cold Store facilities Boolean Domicile oasis of owner (not mandatory, useful only for String cross-check) Id code for plantation Number Code of variety String Number of trees for the variety Number Estimated production (kg/tree) for the variety Number Id code for plantation Number N. of trees aged 0 - 5 years Number N. of trees aged 6 - 20 years Number N. of trees aged 21 - 99 years Number N. of trees aged 100 years or more Number
Table 1 : Database structure : list of fields by table
FIELD WIDTH 4 10 16 4 32 4 4 1 16 4 4
32 10 16 4 4 8 4 4 4 4 4 4
- Satellite image data acquisition As already mentioned in par. 3.1, several types of remote sensing data were acquired for interpretation. Terra ASTER relevant images were downloaded using the WIST2 service, while two different SPOT 5 XS sub-scenes were purchased from E-GEOS. Each acquired images was submitted to image enhancement in order to optimise it for the subsequent interpretation phase. Enhancement techniques included both contrast stretching and high pass filtering. Google Earth coverage was directly used within its application, without any processing operation. - Preliminary legend set up and image interpretation The subsequent step of the preliminary phase consisted in the definition of a preliminary interpretation legend, which was done through an analysis of spectral and pattern characteristics of plantations on the various satellite images, crossed with the analysis of available photographic and bibliographic documentation. Such activity allowed the identification of four different typologies of plantations, according to their cultural characteristics and productive phases. The four classes are described as follows (a more detailed description of each class is given in par. 3.4): Preliminary code N P T S
Description New modern plantation Productive modern Integrated farms Abandoned plantations
On the basis of this preliminary legend, the whole surface of the five oasis under consideration was interpreted using the Google Earth coverage and digitising tools. The very high spatial resolution of such imagery allowed a precise delimitation of each plantation. On the other hand, their quite old acquisition dates made necessary a subsequent updating activity based on more recent images (Terra ASTER images for Al Fugha and Zellah oasis and SPOT 5 XS images for Waddan, Hun and Sokna oasis). - Plantations sampling Planning of field activities included a stratified sampling of inventoried plantations, in order to select a representative sample of plantations to be surveyed in the field. Approximately 20% of polygons has been randomly selected, taking into account the need to proportionally sample, for each oasis, each plantation type. In other words, for each oasis approximately 20% of polygons of each class has been selected, making each plantation class sample proportional to its frequency. 2
Earth Observing System Data and Information System (EOSDIS). 2009. Earth Observing System ClearingHouse (ECHO) / Warehouse Inventory Search Tool (WIST) Version 10.X [online application]. Greenbelt, MD: EOSDIS, Goddard Space Flight Center (GSFC) National Aeronautics and Space Administration (NASA). URL: https://wist.echo.nasa.gov/api/
- Field form design A bilingual (italian/english) field form has been designed to be used during field activities for data collection (see fig. 3). The form is designed in order to record relevant information about surveyed plantations and it is conceptually divided into four sections, concerning respectively: a) general information about plantation localisation b) data about farm size and characteristics c) data about varietal composition, age structure and relevant yields of the plantation d) information about the irrigation system Such form has then been translated into Arabic by the Libyan counterpart in order to make it independently usable by Libyan partners.
Figure 3 : Field Form
3.3 Field survey Field survey was carried out in Al Jufrah during March- April 2010, when Italian experts worked in strict collaboration with Libyan partners in order to perform the following tasks: - Geographical localisation of selected plantations by means of GPS. - Collection of cultural and varietal data, according to the field form prepared, through plants sampling and interviews to plantations owners. - Collection of photographic documentation of sampled plantations. A total of 175 plantations, were sampled over the five oasis concerned. The following table shows the distribution of sampled plantations by oasis and final class. Oasis
Sokna Al Fugha Zellah
N P S T N P S T P S T P T P S T
N. of Sampled sampled surface (ha) plantations 7 22.4 51 244.6 1 2.4 23 282.4 1 2.3 37 97.2 2 88 11 148.4 10 25.5 1 5.8 17 21.4 1 0.5 5 15.3 3 18.3 1 11.3 4 8.9 175 994.8
Table 2 : sampled plantations by oasis During survey, some adaptations to the planned sampling scheme had to be introduced in order to reflect field evidences about plantations types and characteristics; also, field observations allowed to refine the interpretation legend and to better define each class, even adding new, unpredicted classes. The final legend adopted is described in the next paragraph.
3.4 Processing phase Field data collected served as the basis for the final phase of the work, allowing the set up of the final legend, the review of the preliminary interpretation and of the population f the GIS database for subsequent analysis and extraction of statistical figures. - Final legend set up On the basis of field survey data, the preliminary legend was corrected and a new final legend was obtained. Two new classes were added in order to correctly classify particular typologies of dates plantations. Therefore, the final legend utilised include the following classes: Class N New modern plantations This class embraces all new plantations, less than 6 years old and, so, still not entered in the productive phase. Most part of those plantations are specialised ones: no other crops are intercalated within palms rows and irrigation is provided by drip irrigation systems, often fully automated. Only more commercially valuable varieties are present in such plantations, that are mainly composed by Deglet, Kathari and Abel varieties. Nevertheless, mono-varietal plantations are seldom found and a certain variability is always maintained through the cultivation of a few trees of other varieties such as Saiedi and Tagiat.
Fig. 4 - Class N: New modern plantation
Class P Productive modern plantations Productive modern plantations shows similar cultural practices and varietal composition (Deglet, Kathari and Abel being the predominant varieties) of the former class but are mainly composed by plants more than 6 years old and, therefore, already productive. The irrigation system in productive modern plantations is generally localised. In certain areas, where a partial renewal of the plantation has taken place, a mixed irrigation systems (surface and localised irrigation) can be found.
Fig. 5 - Class P: Productive modern plantation Class T Integrated farms This class includes the traditional plantations, where palm date is the main crop but it is integrated with a range of other crops, annual as well as perennial, and with livestock, giving raise to a fully integrated farm rather than to a specialised date palms plantation. Annual crops include cereals such as barley and millet, vegetables such as onions, garlic, tomatoes, peppers, broad beans and others. Among perennial crops, alfalfa is very common because of its particularly high market prices. Also, fruit trees such as olives, oranges, grapes, apricots and pomegranates are often found. Several species of poultry (chickens, ducks, turkeys) are commonly found in such farms, together with sheep, goats and, sometimes, camels. The most widespread irrigation system in traditional farms is the surface system, where water is brought to each plant through a network of surface channels. As for productive modern plantations, is not uncommon to find mixed irrigation systems, combining surface and localised irrigation; generally speaking, a progressive evolution toward this latter method can be noticed.
Date palms belong generally to higher age classes and are usually more than 20 years old. In the more ancient plantations near the city centres of Waddan and Hun is not rare to find very old plants, even more than 100 years old. The varietal composition of such plantations shows a grater variability: the most widespread varieties are Tagiat, Kathari, Hamria and Deglet, but Abel, Bestian and Saiedi are also very common. Furthermore, an high percentage of plants obtained from seed (and therefore not identifiable with any variety) is found.
Fig. 6 - Class T: Traditional farms Class S Abandoned plantations This class include those plantations that do not receive any input anymore. The most widespread varieties in such plantations are Kathari and Tagiat. It is interesting to note that in some abandoned plantations visited in Hun, not receiving water nor other inputs after more than 20 years, about 30-40 % of plants are still alive, even if not producing. In the past, the main reason for abandoning date plantations was the need to renovate the varietal composition, through the introduction of more valuable varieties. Usually, moving to a new uncultivated surface was cheaper than renovating the existing plantation. Similar plantations can be easily found near the towns of Waddan and Hun. Presently, water shortage or salinization are the main cause of abandoning plantations; it is worth to mention that in certain areas (such as the Hammam project area in Sokna), deterioration of physical properties of soils due to poor drainage represent an important cause for abandoning plantations.
Fig. 7 - Class S: Abandoned plantations Class D Not irrigated areas Not irrigated areas represent those areas where the particularly high water table allows the survival of plants and a certain production of dates even in absence of irrigation; therefore, such areas are a very interesting class. Despite of their modest height, most part of date plants in those areas are very old. Most of them can be hardly identified as known varieties, but it is worth to note that in these areas is easy to find minor varieties as Tasferit and Zebur, which are almost never found in traditional plantations, representing therefore a valuable source for biodiversity. Such areas are usually common plantations, meaning that each farmer owns a few (usually 3-5) plants.
Fig. 8 - Class D: Not irrigated areas Class E New developing areas In terms of surface, this class is the most important one, covering more than 30000 ha in the five oasis object of the study. Surfaces included in this class, on the basis of evidences from satellite images, are those where new specialised date palms plantations and/or agricultural projects are expected to be realised in the next few years; in certain areas soil has already been prepared for date palms through the excavation of holes, while in other areas, especially all around Sokna and Hun, most recent satellite images show that delimitation of parcels and/or the realisation of drainage channels is on going.
Fig. 9 - Class E: Expansion areas - Final interpretation On the basis of field evidences, the preliminary interpretation has been fully reviewed and the classification of each polygon has been checked according to the final legend above described. Being the most recent ones, SPOT 5 XS images have been used as reference images for interpretation correction. The most frequent corrections have affected the preliminary Class N ("New modern Plantations"), where for many polygons a migration towards the Class P ("Productive modern plantations") was necessary. Furthermore, the areas belonging to classes D and E, which had not been considered in the preliminary phase, were added. As a result, the final information layer of date plantations for the five oasis was obtained and the relevant thematic maps have been derived. - Field data verification, entry and processing The database structured during the preliminary phase has been populated with data collected during field survey. Data processing and statistical analysis performed on database concerned mainly the production of quantitative figures about: - actual surfaces per plantation class and per oasis; - mean varietal composition of date plantations (relative abundance of each variety) for each oasis. - Photographic database set up The huge photographic documentation has been checked and one/two representative picture(s) for each plantation have been selected and properly labelled.
This pictures subset has then been linked to surveyed plantations polygons in the final version of GIS in order to integrate the cartographic information with a photographic data set describing surveyed date palm plantations.
4. Results The main results of the work are represented by the geographic database and the thematic maps derived from it. 4.1 The geographic database The Geographical Information System of date palms plantations stores the inventory of presently existing plantations as well as of areas of potential expansion. This gives a picture of the situation at the moment of acquisition of the most recent images (July 2009). Plantations inventory is easily updateable provided that more recent satellite images, with adequate spatial resolution, are added to the system. Such inventory is integrated with ancillary information layers such as the Digital Elevation Model (which provides information about the geomorphological aspects of the region) and by the geological map.
Fig. 10 : The Date Palms Plantations GIS layout Furthermore, for the subset of surveyed plantations, the GIS provides information about varieties, their present production, irrigation systems and storing facilities in the farm. Also, the photographic documentation which has been integrated in the GIS provides a valuable source of information on the characteristics of surveyed plantations. The main statistical results of data processing for surveyed plantations are summarised in the following tables.
Wadda Hun Sokna Al Zellah Total n Fugha modern 742.0 91.9 46.0 0.0 10.4 890.3
N P T S D E Total
New plantations Productive modern 1588.6 649.4 113.8 0.5 84.4 2436.7 plantations Integrated farms 646.2 201.3 873.5 22.6 251.5 1995.1 Abandoned plantations 243.0 234.9 214.9 0.2 26.3 719.4 Not irrigated areas 353.7 250.9 382.1 0.0 0.0 986.7 New developing areas 6886.0 9628.5 14428.4 0.0 0.0 30942.8 10459.5 11056.8 16058.8 23.3 372.7 37971.1 Table 3 : Date plantations surfaces by class and oasis
Code H C B X D M A K N O S Y R T L G F Z W
Variety All oasis Abel 9.2 Bamour 0.1 Berni 0.4 Bestian 3.2 Deglet 25.2 Halima 0.1 Hamria 3.7 Kathari 21.7 Noyat Meka 0.3 Omglaib 0.3 Saiedi 2.9 Saila 0.2 Sokeri 1.0 Tagiat 18.4 Talis 0.9 Tameg 0.8 Tasferit 0.2 Zebur 0.4 Other cv 10.9
Sokna 4.0 0.0 0.3 1.2 29.0 0.3 1.3 19.2 0.1 0.7 5.9 0.1 2.5 18.1 1.7 1.2 0.5 0.4 13.5
Hun 6.1 0.0 0.6 1.3 32.8 0.1 1.0 12.6 0.2 0.3 1.7 0.5 0.8 32.1 1.2 1.1 0.3 0.8 6.4
Wadda Zellah Al n 14.8 1.5 Fugha 0.0 0.3 0.0 0.0 0.3 0.0 0.0 3.3 3.2 12.0 24.4 6.0 0.1 0.2 0.0 0.0 0.5 27.1 27.3 33.9 4.3 0.1 0.6 0.0 0.0 0.2 0.0 0.0 2.8 16.7 0.0 0.0 0.0 0.0 0.8 0.6 0.8 9.6 6.1 16.1 0.6 4.2 0.0 0.6 0.6 0.0 0.1 0.7 0.0 0.2 0.0 0.0 6.7 29.0 43.6
Table 4 : Mean varietal composition of plantations by oasis (%) Code H C B X D M A K N O S Y R T L G F Z W
Variety All Class T Class S Class P Class N Oasis Abel 9.3 7.4 2.7 10.0 14.4 Bamour 0.1 0.2 0.0 0.1 0.0 Berni 0.4 0.3 0.7 0.4 0.2 Bestian 3.2 6.0 0.0 2.0 0.9 Deglet 25.2 10.1 0.0 31.7 35.9 Halima 0.1 0.2 0.0 0.1 0.4 Hamria 3.7 10.2 0.0 0.9 0.1 Kathari 21.7 16.4 47.0 23.7 30.0 Noyat Meka 0.3 0.4 2.7 0.3 0.4 Omglaib 0.3 0.6 1.3 0.2 0.0 Saiedi 2.9 2.7 2.0 2.9 3.3 Saila 0.2 0.2 0.0 0.2 0.1 Sokeri 1.0 1.6 4.0 0.7 0.0 Tagiat 18.4 16.5 33.6 19.6 9.9 Talis 0.9 1.1 4.0 0.9 0.3 Tameg 0.8 1.1 2.0 0.6 0.6 Tasferit 0.2 0.3 0.0 0.2 0.0 Zebur 0.4 0.5 0.0 0.4 0.0 Other cv 10.9 24.2 0.0 5.2 3.3
Table 5 : Mean varietal composition of plantations by plantation class (%) 4.2 Thematic maps Four thematic maps (one for each oasis, except for the two small oasis of Zellah and Al Fugha, that are gathered on the same map sheet) have been designed and realised as posters. The main focus of posters is on the cartographic representation of the different plantations typologies; beside, maps are integrated with additional insets providing the main results coming from the studies of pomological and genetic characteristics carried out by the University of Florence as well as the characterisation of the study area from the historical and cultural point of view. The thematic maps scales are variables, ranging from 1:25000 to 1:50000 depending on the oasis surface. All posters are designed to fill an A0 sheet (118.9 x 84.1 cm). A scaled reproduction of such posters in give in Figure 11.
Fig. 11 : Waddan : Main map and ancillary information
5. Conclusions The Geographical Information System of Date Palm Plantations in Al Jufrah region should represent a starting point rather a final result of the study. Considering the rapidly changing scenarios in the study area, the inventory provided by such GIS should serve as a basis for the monitoring of palms cultivation and dates production in the region. Several reasons justify the need for such monitoring: - there are many field evidences that land use changes for large surfaces of desert soils toward irrigated cropping will be hardly sustainable on the medium - long term: in several areas the lowering of water table give already raise to water shortage problems. Together with poor water quality, such shortage cause, in turn, a dramatic increase in soil salinity, as confirmed by many fields observations. Despite of date palms resistance to soil salinity, a decrease of productivity should be expected and it is probably already ongoing in certain areas, especially in Waddan and in the southern part of Hun. Figure 12 compares the presently irrigated surfaces of date plantations with the potential expansion areas detected from satellite imagery. For the three main oasis of Hun, Waddan and Sokna, data show that potential expansion areas for irrigated agriculture are several times greater than presently irrigates plantations: approximately three times greater for Waddan and ten times greater for Hun and Sokna. Lack of exhaustive studies about the hydrology of the whole region does not enable to make forecasts about water availability in the next future, but such figures suggest that particular attention should be paid to a careful water management aimed to a sustainable agricultural development of the whole region.
Fig. 12 : Land utilisation types by oasis
- the analysis of surfaces of each plantation class shows that class N (New modern plantations) cover, in the three main oasis, 880 ha against the 4072 ha of the classes P and T. On the basis of such figures, in the next few years the global dates production should probably increase of about 22%. This estimate does not take into account the eventual new plantations that are going to be realised on the potential expansion areas and therefore is likely to be an underestimation. The impact of such increase in dates production on market prices and the export potentials should also be considered. - The classification of plantations according to the cropping system (specialised plantations, integrated farms, not irrigated areas) and according to their age give the possibility to further process quantitative data in order to get reliable estimates on yearly dates production and its trend over the next period. More precise figures about present and potential future productions of dates should rely on more precise data about actual yields for different varieties and for each age class. As a matter of facts, yields data collected during the field survey are not considered enough to provide reliable estimates about the total production. It is therefore recommended to schedule the collection of such data, preferably in the dates harvest phase. The integration of these data in the GIS will provide a more complete tool for date palms cultivation monitoring in the region.