Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Sustainable development and protection of water resources in arid lands

Auteur : Aidarov, Irina

Université de soutenance : Ben-Gurion University of the Negev

Grade : Master of Science 2006

Résumé
An analysis of the management of limited water resources in arid lands shows that, to date, attention has been paid mostly to economic and technological problems, while environmental damage has been considered as a “progress cost” or has been neglected altogether. This approach to water management is based on a “costefficiency” model. However, it has been found that the “progress cost” can be considerable, and comparable to production costs. In particular, using this approach for the development of agricultural land in the Ily River-Lake Balkhash basin in Kazakhstan led to construction of the rice-irrigation system, characterized by low technical performance, over the sand dune terrain. Heavy water application and high infiltration losses had negative environmental effects : a decrease in the fertility of the irrigated lands, pollution of groundwater and surface water, desiccation of the Ily River delta and violation of the Lake Balkhash ecosystems. The major aims of this research were to assess the negative impacts of irrigation and to develop and apply a model to assess sustainable management of water and land resources in the Akdalinsky irrigated lands of the Ily River basin. A net present value (NPV) criterion of efficiency was used to compare different scenarios of agricultural development in the study area. The NPV criterion accounts for the benefits, in monetary terms, from agricultural production and the costs due to changing soil fertility, salinization and contamination of soil and water resources. Relatively simple models were used to assess the NPV components. Four alternative scenarios of use of water, land and material resources were considered : 1) Exploitation of the existing rice irrigation system with rice fields occupying 62.5% of irrigated land (Soviet era policy) ; 2) Reconstruction of the existing rice irrigation system and changing the structure of the irrigated land by decreasing rice fields to 37.5% of irrigated land ; 3) Development of furrow irrigation aimed at ii production of forage crops for cattle breeding ; and 4) Development of highly efficient irrigation based on sprinkling, also aimed at producing forage crops for cattle breeding. The restrictions in each scenario were maximum available total water consumption, available investments and maintaining water content and salinity of the root zone within admissible limits. Estimation of the economic benefits and ecological costs was based on longterm forecasting of water and salt regimes in irrigated lands as well as on pollution of water resources, using mathematical models of water flow and solute transport (WASTR3-A) and hydrological and pesticide balance (GLEAMS). Results of the simulations and the comparison of NPVs for the alternative scenarios led to the following conclusions : Ecological damage to the irrigated land and water resources depends on the structure of agricultural development, techniques and technology of irrigation. In scenarios 1 and 2, soil fertility decreases and intensive pollution of water resources occurs due to low technical performance of the irrigation systems (water-use and landuse efficiencies of 0.5-0.75 and 0.64-0.85, respectively). The cost of the ecological damage in scenarios 1 and 2 is 1.4 and 1.36 times higher than the value of the benefits from selling agricultural produce. In scenarios 3 and 4, improvement of the irrigation system (by increasing water-use and land-use efficiencies to 0.85-0.95 and 0.90-0.98, respectively) and changing agricultural crop patterns lead to a decrease in water consumption per unit yield, a decrease in pollution and an increase in irrigated soil fertility. In all scenarios, development of irrigated land leads to an increase in natural pasture fertility (especially in scenarios 3 and 4), since forage production on irrigated land decreases pasture load. Scenario 4 was found to be the most efficient and to provide the maximum NPV

Mots Clés : Arid regions ecology — Kazakhstan. — Irrigation — Sustainable development — Water resources development — Environmental aspects — Balkhash Lake (Kazakhstan) — Environmental conditions

Présentation (BGU)

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