Water Productivity at Different Geographic Scales in Zhanghe Irrigation District, China.

要旨

In the context of the increasing cereal demand due to population growth, improvement of water productivity in irrigation systems is of paramount importance. The collection of necessary information to assess the various uses of water in an irrigation system may require a lot of field investigations. The cost increases exponentially for large and especially complex systems like the Zhanghe Irrigation District in Hubei Province, China. In this paper, estimations of rice yield and of seasonal evapotranspiration of rice areas were made using remote sensing and GIS (Geographic Information Systems) techniques. Ground data was limited, yet sufficient to calculate evapotranspiration by energy-balance, and rice yield by radiation-based remote sensing models. Information derived from remotely sensed data was combined with irrigation inflow measurements at four levels of geographic scale of gross irrigated area, namely a field, a medium sized irrigation unit, a Canal Command and the Zhanghe Irrigation District. A water accounting method was used to transform the data into water productivity information.Using the above mentioned tools, it was proven possible to calculate the water-accounting indicators using remote sensing data in a study area where the availability of ground data was minimal, therefore providing important information to water managers within very limited costs. Also, the water-accounting indicators were studied at various geographic scales, and their scale dependency was indicated.