Irrigation water use efficiency in collective irrigated schemes of Tunisia: determinants and potential irrigation cost reduction

This study aims first to measure the farm specific irrigation water use efficiency (IWUE), through non parametric DEA model; and second to evaluate the potential irrigation cost reductions and identify the main factors causing variations in IWUE among the sample farms. Cross sectional data collected from a sample of 75 farms participating in the WaDImena project in Nadhour region (northern Tunisia) was used for this aim. The results showed that the average level of IWUE across the farm sample was around 61.2% under variable returns to scale (VRS) assumption. However, the estimated mean irrigation water technical cost efficiency (ITCE) is much higher than IWUE. Farmers would be able to reduce their actual cost by 5% under VRS by adjusting irrigation water to its efficient level. This low level of cost reductions is consistent with the existing literature about IWUE in Tunisia. Moreover, education level of farmers, access to credit and agricultural extension service showed a positive relationship with the IWUE in our case study.Resource /Energy Economics and Policy,

Irrigation water pricing between governmental policies and farmers’ perception: Implications for green-houses horticultural production in Teboulba (Tunisia)

A positive mathematical programming model was constructed in this study to assess the effect of three water pricing scenarios on Teboulba’s agricultural production systems. The effects of these scenarios were estimated for three groups of farmers from three irrigated districts. Results show that water demand in group 1 remains inelastic until achieving the price of 0.20 TD. A price above this level decreases water consumption, farmer’s incomes as well as seasonal labor demand. For groups 2 and 3, the water demand curves remain highly inelastic even with a full cost recovery price. However, once reaching this last price, the model shows important income reductions reaching 20% of the current observed income. Moreover, a pricing policy aiming to recover operational and maintenance costs and which will be implemented independently from other economic, social and environmental measures can threaten the sustainability of the production systems in the region.Water pricing, positive mathematical programming, greenhouses, economic impact, Teboulba, Environmental Economics and Policy, Farm Management, Resource /Energy Economics and Policy, Q15, Q18,

Investigation of structural effects on the reactivity of heterocyclic bioactive compounds

Tese de dout., Química, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2008In the course of this investigation, structural effects on the reactivity of a series of heterocyclic compounds, in particular tetrazole and benzisothiazole derivatives, submitted to different chemical environments, were explored. The photochemistry of several representative tetrazoles was considered in solution and for the compounds trapped in a rigid matrix of solidified argon at cryogenic temperatures. UV-excitation resulted in photofragmentation of tetrazoles with a wide range of exit channels. Important mechanistic questions concerning the photodecomposition of allyl-tetrazolyl derivatives in different solvents were answered, and new synthetic methodologies for the preparation of heterocyclic compounds, such as pyrimidinones or oxazines, from allyl-tetrazoles, were developed. For the matrix-isolated compounds, since the obtained fragments in general stay in the matrix cage where they are formed, no subsequent cross-reactions involving species resulting from photolysis of different reactant molecules can occur. This fact introduced a useful simplification for the interpretation of the reaction mechanisms. FTIR spectroscopy provided experimental frequencies and intensities of characteristic absorptions of the matrix-isolated chemical species, both for reagents and photoproducts. The analysis of experimental data was assisted by their direct comparison with the vibrational spectra theoretically calculated for the single molecule in vacuum. Spectroscopic characterization of a number of relatively unusual or highly reactive molecules, formed from photolysis of matrix-isolated tetrazoles, is presented for the first time. Novel tetrazolyl and benzisothiazolyl naphthylmethylic ethers were synthesized and the development of experimental conditions for their palladium-catalysed hydrogenolysis, using a hydrogen donor or molecular hydrogen, was carried out successfully. Structural effects on the reactivity of the heteroaromatic ethers were investigated. Furthermore, new benzisothiazole-tetrazolyl derivatives differing on the spacer-group used for linkage of the two heterocyclic systems were designed, produced and tested as multidentate ligands in coordination reactions with transition-metal complexes

Gestion de l'usage d'une nappe par un groupement d'agriculteurs : l'expérience de Bsissi Oued El Akarit en Tunisie

En Afrique du Nord, de nombreux aquifères sont surexploités, principalement du fait d'une agriculture irriguée intensive. Cependant, les politiques publiques qui ont cherché à réguler cet usage se sont montrées jusqu'à maintenant peu efficaces, du fait du manque de moyens et parce que les agriculteurs les considèrent comme peu légitimes. L'article analyse un cas de gestion collective de l'usage des eaux souterraines par les agriculteurs eux-mêmes, dans le cadre d'une association au Sud de la Tunisie. Dans la zone de Bsissi Oued El Akarit, l'administration multipliait dans les années 1990 les procédures de contrôle des puits, conduisant à de nombreux conflits. En 1999, les agriculteurs et l'administration se sont mis d'accord pour qu'un groupement de développement agricole soit créé spécifiquement pour contrôler les puits et forages dans cette zone. Depuis, le groupement a effectivement réussi à mettre en oeuvre un tel contrôle, mais reste toujours fragile financièrement car il ne s'auto-finance pas. Le processus de concertation qui a conduit à ce dispositif de gestion a réussi grâce à : i) la posture de l'administration, à la fois ferme en matière d'application des lois en vigueurs, et ouverte à la concertation avec les agriculteurs, et ii) aux compétences et à la légitimité des leaders du groupement. Cette expérience montre que, dans certains cas, les agriculteurs peuvent devenir partie prenante d'une cogestion des eaux souterraines pour un usage durable de cette ressource. (Résumé d'auteur

Simulation ot the effects of water pricing scenarios on smallholder irrigators in South-Africa

The growing water scarcity worldwide puts pressure on irrigation systems as main consumptive user to improve performance. In developing countries, where today agricultural water use is often still heavily subsidised, a tendency exists of introducing water pricing policies to stimulate rational water use. The exact impact of water pricing policies in terms of water saving or its effect on the farmers¿ production systems remains unknown. This study introduces a new two-stage method that allows estimating at farm level the effects on the agricultural production process and water demand of introducing or raising a water price. In the first stage the technical efficiency frontier is constructed and the technical and allocative efficiency levels of each farm are calculated. This representation of the technology is used in the second stage in a profit maximization model. Applying the method to small-scale irrigators in South Africa, it is shown that water demand of farmers is quite responsive even to small changes in the water price. Furthermore, introduction of a water price is found to significantly decrease farm profit, which is particularly problematic for poor farmers. (Résumé d'auteur

ESTIMATING THE EFFECT OF WATER CHARGE INTRODUCTION AT SMALL-SCALE IRRIGATION SCHEMES IN NORTH WEST PROVINCE, SOUTH AFRICA

In South Africa water law has recently changed, adopting the principle of water as an economic good, thus levying charges on its use. For small-scale irrigators this is an important change, because currently their water use is entirely subsidized. In the coming years, subsidies will gradually decrease and an essential expected benefit of this policy change is that water use efficiency will rise, leading to reduced consumption and possible reallocation of the water saved. The exact impact of the water pricing policy on the irrigation water use or on the farmers' production system is however unclear. This study introduces a new methodology, based on data envelopment analysis, that allows estimating the effects on the agricultural production process and water demand of introducing or raising a water price. It is revealed that a large majority of the farmers does not adjust water use. Production costs however were shown to increase significantly.Production Economics, Resource /Energy Economics and Policy,

Sigmatropic rearrangements in 5-allyloxytetrazoles

Mechanisms of thermal isomerization of allyl tetrazolyl ethers derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol were investigated. In the process of the syntheses of the three 1-aryl-5-allyloxytetrazoles, their rapid isomerization to the corresponding 1-aryl-4-allyltetrazol-5-ones occurred. The experiments showed that the imidates rearrange exclusively through a [3,3¢]-sigmatropic migration of the allylic system from O to N, with inversion. Mechanistic proposals are based on product analysis and extensive quantum chemical calculations at the DFT(B3LYP) and MP2 levels, on O-allyl and N-allyl isomers and on putative transition state structures for [1,3¢]- and [3,3¢]-sigmatropic migrations. The experimental observations could be only explained on the basis of the MP2/6-31G(d,p) calculations that favoured the [3,3¢]-sigmatropic migrations, yielding lower energies both for the transition states and for the final isomerization products

PERFORMANCES AND EFFICIENCIES OF THE IRRIGATION WATER USERS’ ASSOCIATIONS IN TUNISIA

This article analyzes the efficiency of Water Users Associations (WUA) in the Cap Bon region (Tunisia) and studies its main determinants. The analysis is performed in two stages. First, the efficiency is measured via the nonparametric “Data Envelopment Analysis” (DEA) technique. The DEA models are constructed not only to assess the overall WUA efficiency but also to evaluate the management and engineering sub-vectors efficiencies separately through a mathematical modification in the initial DEA model. In a second stage critical determinants of efficiency are determined using a Tobit model. In this analysis the focus is on technical (characteristics of the irrigation area and network), organizational and administrative variables. Results show that on average 18.7% of the used inputs could be saved if the WUA would operate on the frontier. The average scale efficiency, which can be calculated as the ratio between Constant and Variable Returns to Scale efficiency measures was around 71%, indicating that many WUAs are not operating at an efficient scale. Subvectors efficiencies show that WUAs present better performances in maintenance activities than in management. The inefficiency found can furthermore be mainly attributed to the number of years of experience in operating a WUA in addition to the number of water pumping stations managed and the rate of the exploited area. The scale inefficiencies are mainly due to administrative and organizational variables.WUA, irrigation, efficiency, DEA method, Institutional and Behavioral Economics, Land Economics/Use,

Effect of changes in the institutional structure of irrigation water property rights on the willingness to pay of farmers for water: case of Tunisia

This paper assesses the economic value of changes in the attributes of farmers’ irrigation water property rights in Tunisia. Changes on attributes generated by the transfer process of the property rights from the collective to the individual level in addition to changes in “constitutional” attributes were integrated into three scenarios. The valuation was conducted using the Contingent Valuation Method through the elicitation of individuals’ willingness to pay. Results show positive willingness to pay values for all scenarios. However, farmers of the studied region are shown willing to pay more for changes in the constitutional attributes. Furthermore their willingness to pay appears to be most affected by their perceptions concerning the organization and the functioning of the water users’ association to which they belong and by their productivity.Property rights, irrigation water, Contingent Valuation, Resource /Energy Economics and Policy,