Local Adaptations under Tunisian Oasis Climatic Conditions: Characterization of the Best Practices in Water Agricultural Sector

1L. Dhaouadi, 2N. Karbout, 1K. Zammel, 3M.A.S. Wahba and 2S. Abdeyem 1Regional Center for Research in Oasian Agriculture, Km1 Route de CP:2260 Deguache, 2Arid Regions Institute (IRA), 4119 Medenine, Tunisia 3Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources Research, Bejing, China

Key words: Oasis, climate change, irrigation water Abstract: For a long time, the governance of water management, date palm, stakeholders, community resources in oases presents great challenges for local and governance national stakeholders with the consideration of economic, social and environmental importance of this complex ecosystem. So, it’s very important to understand its behavior under current and future climate change conditions. This study focuses on diagnosing, identifying, characterizing and capitalizing the most practices of irrigation water management in the Tunisian oasis and selecting the best among them and to disseminate it in the oasis communities through workshops, field days and Corresponding Author: school days. The most capitalized best practices found L. Dhaouadi during this study are: community governance of irrigation Regional Center for Research in Oasian Agriculture, Km1 water distribution in the oases of El Guetar, valorization Route de Tozeur CP:2260 Deguache, Tunisia of the oasis heritage through the labialization SIPAM (case of the historic Oases of ), Improved gravity Page No.: 57-64 irrigation Basin system under date palm in the Oases, the Volume: 15, Issue 4, 2020 sandy amendment at the level of oasis agricultural parcels, ISSN: 1816-9155 gravity Bubbler irrigation system in date palm groves and Agricultural Journal magnetic treatment of irrigation water and mixing of Copy Right: Medwell Publications irrigation waters to improve their qualities.

INTRODUCTION agrosystems have played an important role in the development of the arid areas and the settlement of In the arid and semi-arid areas, agriculture has humans in these areas through providing various concentrated in regions where water is available. The ecosystem services such as supplying food and fodder, Oasis agrosystem is an intensive man-made farming managing available natural resources such as water and system associated with the cultivation system in arid and soil as well as enhancing biodiversity under local climate semi-arid areas. Oasis are mainly found near underground condition[1]. Additionally, Oasis agrosystems can help to aquifers where water can reach the surface naturally and mitigate the negative effects of climate change in dryland can be extracted through pumping. For a long time, Oasis areas, they are seen as the opposite to desertification

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and land degradation and thus, they have the potential CRDA. In Tunisian southern Oases date palm groves are to contribute to carbon sequestration in the arid irrigated through the surface irrigation system. Farrow and areas[2, 3]. basin techniques are considered as modified forms of In Tunisia, Oases date back to ancient times and the flood technique in which water is directed to flow through survival of these agrosystems was a result of the adapted narrow channels established between palm trees rows. traditional management practices of the people living at While this method is less expensive and easy managed in the oases. Traditional oases for instance have a significant flatted lands nevertheless, the technique suitability in role in terms of economic growth not only for the country sandy soils is rather low due to high loss of water through through date’s production but also for the rural towns and leaching and evaporation. The depletion of water communities, they create jobs and support biodiversity. resources is clearly a major problem in the Southern Different studies have highlighted the socio-economic Oases of Tunisia, the so, called illegal extension of Oases importance of the oasis agrosystem for the economic as a result of private initiatives and access to water growth of the rural communities as well as for the state through digging wells has led to over-extraction of economy[4]. renewable ground water and accelerating phenomenon of Oases cover a total area of 40803 ha; they stretch saline intrusion from the saline areas (e.g., Chott in from the Mediterranean coast in the east to the Grand Erg )[7]. In addition, most of the farmers managed the Oriental in the West and from Gafsa Mountain in the water in their own way in the absence of a specific North to Sahara in the South of the country. recommended method which leads to considerable water Geographically Tunisian Oases are classified into two loss[8]. So, the continuous decline in water availability will origin categories based on the typology of the Oasis, the affect the region through increasing land vulnerability to coastal Oasis which cover 17% of the Oases total area and desertification and bring the agriculture at risk. Water the continental Oasis which cover 83% of the Oases total problems in Oasis are expected to surge by the climate area and produce more than 89% of date production in the change impacts through extensive drought events[9]. country (dominated by DegletNour variety). The Tunisian Oasis are expected in the influence of a warming continental oases are divided into Saharan Oasis and of 1.1°C by 2030 and 2.1° C by 2050[10]. Date production mountain Oasis. Saharan Oasis are located in the northern is expected to be severely affected as a result of this Tozeur region and scattered around Chott El-Jerid in change; the areas where date palm grows may become Kebili Governorate[5]. Most of the mountain Oasis are unsuitable to support an economic production of the concentrated in Gafsa region and cover 2, 38 ha (6% of crop[11]. Climate change is predicted to reduce the Oases total area). growing period of the plants and thus date cultivation is Tunisian Oasis are facing a number of threats such as subjected to change to attain higher crop production, low productivity, deterioration of water resources, soil farmers are thus need to consider tolerant varieties to salinization and increased pests and diseases associated drought and best management practices to adapt to these with biodiversity loss[6]. These threats are coupled with effects[12]. land mismanagement practices such as over exploitation Since, groundwater is the major source of water in of natural resources, especially, water which affects the Oasis, the overuse of this water under arid and semi-arid Oasis agrosystem survival and therefore their role in conditions is a serious problem for the long term maintaining the livelihoods of the local inhabitants. In agricultural sustainability in these unique areas. It needs Tunisian Oasis, ground water is the the main source of integrated management strategies for the safe use of all irrigation water. The underground water that supply available water resource including drainage water, southern Oases comes from two of the largest aquifers in brackish ground water. Wahba[13] studied different the world, the Terminal Complex aquifer, a small part of strategies for using agricultural drainage water for which is under Tunisia and the Continental Interlayer. In irrigation over a 20-year period using simulation the South is the Jeffara aquifer that fed mainly from modeling and recommended the strategies of deficit overspill from the Terminal Complex aquifer extends irrigation combined with controlled drainage, cyclic use under the Jeffara coastal plain between Gabes and . of agricultural drainage water of 4-12 dS mG1 with fresh Others, much smaller aquifers also exist in these regions water and the inter-seasonal cycling of drainage and fresh that are recharged from drainage water in Oases and from water. In this context this study is to diagnosing, flooding in small wadis. Water management of irrigation identifying, characterizing and capitalizing the most water is carried out by Collective Interest Association practices of irrigation water management in Tunisia oasis (AIC) and the water distribution is made based on the and selecting the best among them and to disseminate it irrigation schedule decided by AIC with the assistance of in the oasis communities through workshops, field days, Regional Commissariat for Agricultural Development and school days.

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MATERIALS AND METHODS sandy soils of the Oasis are characterized by high permeability and low water retention. Groundwater and Site description: The study was conducted at South soil salinity varies with water table depth. Mountain Tunisian Oases (Fig. 1), coastal Oases in Gabes, Gafsa oases are characterized by desert climate, the continental Oases in Kebili and Tozeur and mountain annual precipitation reached a maximum of 203 mm; the Oases in Gafsa. Coastal Oases stretch along the coast of summer temperature can achieve a maximum of 30.5°C Gulf of Gabes in the south east of the country. Whereas in July and falls to reach 11°C in winter (January). The continental Oases is located in Kebili and Tozeur region mountain oases are classified as calcareous soil according South-West Tunisia, the Oasis location is to the west and to WRB. adjacent to Chott Djerid (a salt plain) and mountain oases located in Gafsa region in the Southwest of Tunisia. Data collection tools and field campaign: The study has Costal Oases climate is Mediterranean dry, hot in summer targeted about 55 agriculture, 13 from Tozeur Oases, 14 and mild in winter. Rainfall is low and erratic with an from Gafsa oases, 18 from Kebili Oases and 10 from annual average of 186 mm. Under the influence of Gabes Oases, to fill the individual questionnaires 55 Saharan winds, the summer temperature can reach 42.5°C respondents were interviewed in March, 2018. Before in August and falls to reach 5°C in winter in December starting with the individual interviews, we collected data and January. The winds blow between December and using the documents available from the Regional April are cold, dry and carrying sand. The soils of the Development Commissariat (RDCA) and the Regional Oasis are gypsum calcareous, according to WRB Research Center for Oasis Agriculture (RROA) to retrieve classification; it can be classified as Gypsisol. On the information about the Oasis conditions, based on the data surface there are several meters of sand gypsum limestone collected on formulating the questions of the individual which forms crust gypsum layer. The soil of the Oasis questionnaire, i.e., completing the different agriculture is alkalized (pH 7.22-8.68)[14]. Continental Oases are practices to reduce water losses in Oases systems. Due to characterized by a desert climate, the annual precipitation homogenous characteristics of the farmers, a simple is irregular and <90 mm and the temperature is very high random sampling technique was used to select the during the summer (maximum 55°C in July). Evaporation respondents. To save time and to facilitate the process of can reach 2000 mm per year. In the spring and summer filling the questionnaires, most of the farmers were seasons, the strong hot winds of sirocco blow carrying reached during their presence in the Oasis; some of them sands from the desert into the Oasis. The continental were met in public places in the village or at their houses oases are classified as Gypsisols according to WRB. The (Fig. 2).

7° 8° 9° 10° 11°

34°

33°

32°

31°

30°

Fig. 1: Localization of oases system

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Fig. 2: Survey process

RESULTS AND DISCUSSION water from one board to another (Fig. 3). These manholes are placed at the high points of the plot to ensure gravity Based on our survey the best agriculture practices in water distribution, life span of this system is around Oases of South Tunisia to reduce water losses and 30 years to ensure not only a good exploitation of improve production are: available water resources but also to increase the agricultural production in irrigated areas. The buried Governance of irrigation: The improvement of irrigation pipeline system meets water needs, agricultural products system is a crucial issue in the national land use and and various agricultural works have good quality as well regional development strategy. Bases on these reasons the as good management of water resources in better service irrigation system in the Oases has gone through several during network outages. According to the survey results stages. In traditional Oases, farmers irrigated their plots 45% of farmers use this technique. using the traditional submersion technique; water is The change of irrigation distribution system assure distributed by traditional system “seguias” in the ground the reduction of water loss and the impact of climatic from one board to another in the Oases. But because of change in water efficiency in Oasis system[15] but the climatic conditions of the region of southern Tunisia the major problem of farmer’s in the Oases is water this irrigation system increases water losses by Delivery return which was ensured by the Agricultural evaporation to reduce this impact and following the Development Group (ADG)[16] but after our survey actions of the national water saving strategy, the with farmer’s, the percentage of dissatisfied with the traditional “ground seguias” are replaced by concrete functioning of ADG achieve 62%. “seguias”, this new water distribution system in the Oases In South Tunisia, the Oasis of El Gtar made the makes it possible to reduce water losses by infiltration and exception by installing software in partnership with the allow a better distribution of water, to reduce more the Regional Development Commissariat of Agriculture. The water losses, under the action of national water saving research of this software started from 2016. The software strategy. The main objective of this strategy is to is under the name ‘irrigation water management system’ rationalize the use water in agriculture and to obtain the (Fig. 4), the aims are to monitor consumption indicators best economic benefit and to keep the demand for and plan follow the order of water distribution, irrigation at a level compatible with the available water specify the area irrigated by farmers, monitor the resources. To achieve these goals a new irrigation operating cost per hour of the market (cost and sale price), distribution system was installed in the Oases, this system ensure control and good management of the equipment is composed with manholes linked together with buried and to help the ADG in keeping daily expenses and pipes on PVC with 200 mm of water capacity to carry receipts.

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Fig. 3: Water distribution by buried pipeline

Fig. 4: Irrigation water management software interface

Amelioration of water quality: Water governance is an widespread technique in the Oases of South Tunisia and important strategy in the Oases system of south Tunisia, used by 85% of farmers according to our survey is the but the challenge in the Oasis is the quality of water technique of mixing water, this operation is carried out in especially under current climate change which favors the a storage basin (Fig. 6). This basin is constructed accentuation of several problems such as salinization. The downstream from wells or irrigation terminals in order to survey indicated that farmer’s are using solutions to improve the physical quality of irrigation water by settling improve the quality of irrigation water such as magnetic solid debris and increase the flexibility of irrigation flow treatment (Fig. 5) with this technical the water passes and time. The basin also makes it possible to make a through a magnetic water softener, according to the mixture between private well water and the water principle of Lorentz force[17, 18]. We found this technique supplied with ADG to decrease the salinity and in Oasis of in the Governorate of Kebili and the reduce water temperature. The construction of this Oasis of Hezoua in the governorate of Tozeur but limited basin is part of the action of the national strategy of only to 4% of farmer’s, because of the very high cost water saving and it is subsidized by the state with which can exceed 2000 euro per unit. The most 60%. With this technique, the farmer’s has obtained

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Fig. 5: Water magnetization device

Fig. 6: Water storage basin

good results in terms of improving the quality of irrigation system like the hydromorphie and loss of water. On the water. There are also good options to follow the other hand, only 13% of farmer’s installed localized recommendations by Wahba[13] to apply the cyclic use of irrigation systems, 8% used perforated duct irrigation or fresh water with drainage water and to apply the deficit drip irrigation, this agriculture confirmed the efficacy of irrigation under water shortage condition to achieve the these methods in the amelioration of production but the equity distribution of available water resources amoung major problem of this two systems are the clogging of the different farmers. These options will help in utilizing all pores of the irrigation system. About 5% of other farmers available water resources in a sustainable 3 manner and used bubbler irrigation (Fig. 7), this technique was maintain accepted crop yields under the conditions for adopted in 2011, the farmers of Hezoua 2 and Hezoua 5 arid and semi-arid during water shortage periods. used this technique have confirmed that they are very satisfied also according to our survey; this technique is Amelioration of irrigation system: According to our effortless and easy to be installed. The advantages of this survey, 87% of farmers used surface irrigation with irrigation system are the reduction of duration of irrigation different methods by basin or by submersion, these when we compared with the traditional basin irrigation. techniques despite their extent in the most Oases of To confirm the information given by the farmer’s Southern Tunisia but deepening many problems in Oases perception, the research work by made by Dhaouadi,

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Fig. 7: Bubbler irrigation system in the oasis of Hazoua 5 (Tozeur)

Fig. 8: Sand-manure amendment in oasis system of South Tunisia confirmed that the bubbler irrigation system is the best drying out, therewith sustaining microbial life, and system in reduction of water evaporation because the secondly, it elevates the land surface and thereby bubbler irrigation maintained the water directly in the root increases the distance to ground water. The latter finally zone consequently the deep percolation reduced. Also helps to prevent salt accumulation from capillary rise according the study of Dhaouadi etc., the comparison and evaporation of the ground water. The study by between three irrigation techniques: mini diffuser, Karbout et al.[16] confirmed that the addition of underground and bubbler, showed that the best sand-manure amendment in Oasis system improve soil performance was obtained during bubbler irrigation[19]. physical propriety and consequently ameliorate water retention also the study by Karbout etc., confirmed that Amelioration of soil propriety: According to our survey, the sand-manure amendment provided soil moister and 95% of agriculture in Oases of South Tunisia applied the reduce water evaporation. sand and organic amendment (Fig. 8), this soil amelioration carried out in November and December. The CONCLUSION sand-manure amendment in the soil is able to store water for plant growth and when moist it additionally supplies The sustainability of the Oasis ecosystem requires nutrients via. an active soil microbial community[20]. environmental, social and economic management of The sand cover on top of the incorporated manure then natural resources. This management is considered as a exerts two additional positive effects: firstly, it protects great challenge to contribute the sustainability of Oasis the manure from direct heat of the sun and thus, rapid territory. The survey showed the presence of different

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