Lessons from the long flow records of the Nile: determinism vs indeterminism and maximum entropy

Koutsoyiannis, D; Georgakakos, A

dc.contributor.author	Koutsoyiannis, D	en
dc.contributor.author	Georgakakos, A	en
dc.date.accessioned	2014-03-01T02:54:12Z
dc.date.available	2014-03-01T02:54:12Z
dc.date.issued	2006	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/36709
dc.title	Lessons from the long flow records of the Nile: determinism vs indeterminism and maximum entropy	en
heal.type	conferenceItem	en
heal.publicationDate	2006	en
heal.abstract	Three long records of the Nile River are analyzed. The first is the 131-year long contemporary record of monthly flows at Aswan (1870-2001). The other two are the records of annual maximum and minimum water levels from the Roda Nilometer for an 813-year period (640-1452). These records compose the longest instrumental data set available worldwide and their importance in understanding and modelling hydroclimatic behaviours is obvious. Spectral and chaotic dynamical analyses of all records do not provide clear evidence of deterministic signatures except for the obvious annual periodicity. Stochastic analysis suggests that all records have virtually identical long-term behaviour characterized by long-range dependence with Hurst coefficient around 0.85 both on annual and monthly basis. Notably, the long term behaviour departs from simple scaling in a manner that implies uncertainty on large time scales even higher than that of simple scaling, which is known to be already very high compared to typical short-range dependence processes. An explanation of the observed long-term behaviour is sought based on the principle of maximum entropy. Maximization of entropy both on local and global temporal setting produces a dependence structure that is asymptotically (i.e. for large time scales) scaling and seems to be in accordance with the observed behaviour of the Nile records.	en