Integrated water resources management model for the Syr Darya basin

The framework for the model covers: (1) physical and technical management of water resources due to new developments; (2) growing competition for water among agricultural, industrial, urban, and instream uses along the entire basin; (3) increased attention to environmental impacts of anthropogenic interventions; and (4) the complex relationships and implications of water allocation mechanisms and policies on economic efficiency. The model includes: hydrological components, which account for flow and pollutant transport in the river basin network, including the crop root zone; crop production functions, including the effects of both water stress and soil salinity; the benefit functions for instream-water uses; irrigation and drainage management components; institutional rules and policies that govern water allocation; and economic incentives for salinity control and water conservation. The crop production function presented is a critical connection between these components. In this function, crop yield is a function of the balance of soil moisture and soil salinity, and these are further related to the water and salinity balance in the entire basin. In this way, crop yield is related to the performance of the entire hydrologic system and also determines the irrigation benefit in the economic relationships of the model. The modeling framework is applied to the Syr Darya River in the Aral Sea basin of Central Asia, where irrigation is the dominant water use, and soil and water salinization are major environmental problems. This case study is used to argue that the kind of integrated model presented here is critical in sustainable water management analysis. (Author abstract, modified)