In the Mediterranean region, climatological factors make combined sewer ove
rflows a major urban pollution problem that should be monitored and control
led. Some online management solutions require the use of real-time models t
o forecast flows at the most sensitive points of the combined sewer systems
. These models need a very good time and spatial resolution of the rainfall
field, which is not sufficiently reproduced by a conventional rain-gauge n
etwork. This paper presents a case study where the use of rainfall estimate
s from weather radar pictures is compared with the use of a rain-gauge netw
ork in terms of the ability to predict sewer flows in an urban basin in Bar
celona, Spain. The results show that the use of radar data enables the comb
ined sewer systems model to improve the reproduction of observed flows, and
they provide support for the idea that the spatial description of rainfall
is a key problem in modeling the events giving rise to combined sewer over
flows.