Integrated modelling of water availability and water use in the semi-arid Northeast of Brazil

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 Brazilian-German research project. This paper gives an overview of the integrated hydrological and water use modelling for the federal Brazilian states of Ceará and Piaui covering an area of over 470 000 km2. The model subdivides the area into administrative sub-units (municipalities) of in average about 1000 km2. 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 soil moisture), influence of climate and land-use changes on 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 presente