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%                    B O F / I N T R O . T E X 
%                    doc: Thu Mar 16 12:47:13 2000
%                    dlm: Sat Jun  3 15:29:36 2000
%                    (c) 2000 A.M. Thurnherr
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In this chapter the low-frequency (with time scales of weeks or longer)
response characteristics of a simple basin/sill system (intended to
represent the rift valley of the \A segments) are investigated with an
analytical and numerical model. In \rsecNP{BOF-model} the
\OneAndAHalfLayer model consisting of a deep basin and a hydraulically
controlled overflow is formulated. In \rsecNP{BOF-analytic} the
governing equation is solved analytically for steady inflow into the
lower layer. The solutions show that adjustment of the outflow to
abrupt changes at the inflow takes place over timescales of weeks to
months when using parameters representative of the \A segments.
Numerical solutions \rsec{BOF-numeric} show that the model basin acts
as an effective low-pass filter for oscillatory and event-like
disturbances at the inflow. The chapter concludes with a discussion in
\rsecNP{BOF-discu}. 

