Integrated Basin Modeling

Abstract

"River basins are complex areas, combining the natural processes of precipitation, evapotranspiration, surface water and groundwater runoff with man-made features such as dams and reservoirs, diversions and irrigation schemes, and industrial and urban water uses. Computer models may be constructed to represent these natural and man-made processes. Such models are used to help understand processes that are difficult to measure (such as evaporation) and to study the effects of changes in land cover, water management or climate on the natural and man-made processes. Usually, these models are made at a particular scale. For example, a natural river basin or an irrigation scheme may be modeled. This approach neglects the interactions between processes at the different scales.

"In this study, we combine models at threedifferent scales; the field scale, the irrigation scheme scale and the basin scale. The advantage of this approach is that we can obtain information at one scale and apply it at other scales. For example, the productivity of an irrigation scheme could be computed using only information about that scheme. This, however, would miss the links between the irrigation scheme and other upstream and downstream water users. By using different scales we can include these links and look at the irrigation scheme within the context of the basin.

"This report describes multi-scale modeling using, as an example, the Gediz basin in western Turkey. This basin contains large reservoirs, diversions, irrigation schemes and has industrial and urban water consumptions. Three linked models were built, which enabled us to look at both water productivity at the three different scales and what the impacts of changing water availability, management practice, and climate might be on irrigation productivity and on the other water users within the basin."