Sir:

This will be a good research agenda - water indexing. On a per demand basis, in our country we set it at a minimum of 50 liters per capita per day. World Bank has a higher figure - about 70 to 80 liters, per day per person.

On the Water Dependency Index (WDI)

The comprehensive water balance expresses the amount of virtual water associated with food products trade and defines a "Water Dependency Index" (WDI), which represents the part of net virtual water in the total food demand water equivalent. This assumes that the allowance in Blue Water to irrigation must adjust to the available water once the direct needs insured.

The Food Demand Water Equivalent (FDWE) includes water equivalent of Agricultural Production consumed on the local market and the water-equivalent of agri-food imports. The water equivalent of agricultural production includes green water-equivalent and blue water equivalent.

The "Water Dependency Index" (WDI) defined by Besbes et al. (2002, 2010) represents the net equivalent of Virtual Water volumes (Imports-Exports) within the total food demand and is expressed as: WDI = (IMP-EXP) / FDWE.

If one refers to international literature, the concept of water dependency, as defined by FAO (2003), relates only to blue water; it expresses the external renewable water resources (originating outside the country) as a percentage of the total renewable water resources (internal and external). This definition has been largely used by the scientific community as well as by international organisations.

Based on water footprint concept, Hoekstra and Mekonnen (2012) defined the ‘virtual water import dependency’ of a nation as ‘the ratio of the external to the total water footprint of national consumption’ where total ‘water consumption’ refers to the ‘water needed for the production of the domestic demand for goods and services’. The indicator is conceived to reflect the extent to which a country relies on imports of water in virtual form. The results reported by Hoekstra and Mekonnen (2012) on water dependency give, as it may be expected, high values for water-scarce countries (like Jordan 86%, Israel 82%, Yemen 76%, Lebanon 73%). These results reveal however some striking points; in particular, some water-rich countries such as Italy, Germany, the United Kingdom, and The Netherlands have surprisingly high water dependency indexes between 60–95%.

By relating the Water Dependency Index to agricultural water, the indicator proposed by Besbes et al. (2002, 2010)attempts to go beyond the appraisal of the water dependency level of nations to specify the balance sheet items related to the national food demand. As the net equivalent of virtual water represents the difference between the total food demand water equivalent and the total food production water equivalent, the Water Dependency Index (WDI) could be more explicitly detailed in order to bring out the different contributions to food production: "Blue Water" referring to the use of ground and surface water as well as non-conventional water resources, "Green Water" referring to the water reserves of the soil effectively used in crop production or into direct grazing, and "Virtual Water" referring the flux of the "net virtual water import". The objective is to consider the extent to which greater value for all water resources could be achieved.

As the major part of water resources is directly or indirectly used in food production, the WDI related to food balance is in itself sufficient to reflect the National water security by measuring the level to which a nation relies on foreign water to ensure its food demand. This indicator could be consolidated by financial indicators, for instance, the coverage rate of the agri-food trade balance. The improvement of the food security of a country expressed in terms of WDI will depend on the capacity of the country to improve food productivity either in the irrigated sector (Blue Water, including non-conventional water resource) as well as in the rain-fed agriculture and direct grazing (Green Water). From this point of view, the WDI appears as a major decision-making tool for sustainable water resources management. It is also a learning tool as well as a 'discussion-support' tool that provides a common platform for the coherence of the activities of different actors and stakeholders.

Reference:

Book National Water Security, Case Study of an Arid Country: Tunisia

See Also:

https://www.researchgate.net/post/Scientific_Watch_on_Water_Scarcity_Indicators

Attached is a BOOK REVIEW by Ghislain de Marsily (Académie des Sciences, Paris) devoted to the fundamental Water-Food Nexus in the Arid Region taking Tunisia as an example. "National water security– Case study of an arid country, Tunisia (Authors: Besbes, Chahed Hamdane), Euro-Mediterranean Journal for Environmental Integration (2019) 4:11". The Previous French version of the book is available in chapters on:

https://www.researchgate.net/publication/356650449_Securite_Hydrique_de_la_Tunisie_Preface_Introduction https://www.researchgate.net/publication/356662490_Les_Problemes_de_l'Eau_dans_le_Monde

https://www.researchgate.net/publication/356663902_Cinquante_ans_de_politiques_de_l'eau_1960-2010

https://www.researchgate.net/publication/356665641_Le_Bilan_Hydrique_National

https://www.researchgate.net/publication/356666107_Le_bilan_Hydrique_Integral_Eau_Bleue_Eau_Verte_et_Eau_Virtuelle

https://www.researchgate.net/publication/356666288_La_gestion_de_la_demande_en_eau_et_les_ressources_non_conventionnelles

https://www.researchgate.net/publication/356674959_Securite_Hydrique_de_la_Tunisie_les_questions_en_debat

https://www.researchgate.net/publication/356678805_Securite_Hydrique_de_la_Tunisie_Conclusion_Postface

Abstract:

This is a short review of a book recently published by Springer entitled: National water security–Case study of an arid country, Tunisia; by Mustapha Besbes, Jamel Chahed, and Abdelkader Hamdane. It shows that around 40% of the water consumed in Tunisia is imported as virtual water, used in other countries to produce goods. Water security is thus strongly linked to food security, but includes protection of the resource from pollution, accidents, malicious acts, and anticipation of extreme hydrologic events. A detailed analysis is made of water consumed by agriculture for food production by both rain-fed and irrigated crops, from which a surprising conclusion can be drawn: the major part of Tunisian food production is provided by rain-fed agriculture. Therefore, optimizing the yield of rain-fed agriculture becomes a priority. Alternative water resources are also discussed, as well as water governance. Results can be integrated into the policy choices related to sustainable water management which should be made in the future in Tunisia, and other regions where water is scarce.

Climate Change & Agriculture in the Arid Region, an example of Tunisian Olive Groves adaptation to bioclimatic conditions: The olive tree has been cultivated in Tunisia since Roman times under different bioclimatic conditions in exclusively rainfed groves: in the south with less than 250 mm of rainfall and in the north with more than 600 mm [1]. Apart from the different olive tree species in each of the regions, it is clear that the density of olive trees is strictly correlated with rainfall, ranging from 16 olive trees per hectare in the South to nearly a hundred olive trees per hectare in the North; so that it is possible to faithfully superimpose the density map of olive trees on the map of isohyets. Empirically, over millennia and outside of any protocol or procedure, the peasants have naturally adapted to the natural conditions of the environment, and it is difficult to imagine that things can be otherwise.

[1]

Book National Water Security, Case Study of an Arid Country: Tunisia

See also:

https://www.researchgate.net/post/Water_Footprint_Water_Colors_Blue_Water_Green_Water_Grey_Water_Virtual_Water

https://www.researchgate.net/post/Climate_Change_Water_Resources