Scarcity of water resources is a major constraint for development in the semi-arid Northeast of Brazil. Quantification of natural water availability and of water use are key issues within a comprehensive Brazillan-German research project. This paper gives an overview of the integrated hydrological and water use modelling for the federal Brazilian states of Ceara and Piaui covering an area of over 470 000 km(2). The model subdivides the area into administrative sub-units (municipalities) of in average about 1000 km(2), and uses daily time-steps. The hydrological module is designed to account for: water availability (in terms of river runoff, reservoir storage, groundwater recharge and coil moisture), influence of climate and land-use changes an water balance, large spatial scale (acknowledging the uncertainty of model results in view of scarce data), and specific semi-arid hydroclimatological conditions. This version of the water use module includes domestic, animal and irrigation water uses. The withdrawal water use and consumptive water use can approximately be calculated for the present situation of the municipalities. First results of the two modules and the effects of their interlinkages are presented. (C) 2000 Elsevier Science Ltd. All rights reserved.
