1 Spatial Modelling of the Terrestrial Environment - Georeferencial

Editorial: Spatial Modelling
in Hydrology
Richard E.J. Kelly
The simulation and prediction of hydrological state variables have been a significant occupation
of hydrologists for more than 70 years. For example, Anderson and Burt (1985) noted
that Sherman (1932) devised the unit hydrograph method to simulate location-specific river
runoff with a very simple parameterization and data input. Clearly introduced before the
availability of high performance and relatively inexpensive computers, this method ‘was
to dominate the hydrology for more than a quarter of a century, and (is) one which is still
in widespread use today’ (Anderson and Burt, 1985). The approach is spatial inasmuch as
it represents in a ‘lumped’ fashion upstream catchment processes convergent at the point
where runoff is simulated. While the unit hydrograph has been a very useful tool for water
resource management, hydrologists have sought to ‘spatialize’ their methodologies of simulation
(and ultimately prediction) to account for variations of catchment processes in two
and three spatial dimensions. A primary need to do this has been to be able to represent
systems dynamically and especially when a system is affected by an extreme event, such
as a flood. Conceptually, this shift towards understanding and accounting for complex hydrological
process, has manifested itself in the form of a move towards physically based
models and away from simple statistically deterministic models. From the 1980s onwards,
and perhaps inevitably, the availability of relatively high performance computers that could
undertake vast numbers of calculations has allowed the numerical representation of distributed
hydrological processes in a catchment. As a result, the propensity for models to
become complex has only been a small step on. Now, complex hydrological models can
be executed, in standard ‘desktop’ computer environments. Furthermore, the challenges
facing hydrologists engaged in simulation and prediction are not so much those of technology
(although this aspect is constantly pushed forward by ever demanding requirements
Spatial Modelling of the Terrestrial Environment. Edited by R. Kelly, N. Drake, S. Barr.
C○ 2004 John Wiley & Sons, Ltd. ISBN: 0-470-84348-9.