An Investigation on Changes and Prediction of Urmia Lake water Surface Evaporation by Chaos Theory

Abstract

<p>Chaos theory discusses unstable and non-periodic behavior of non-linear fluctuating dynamic<br />systems. Since evaporation level variations of lakes have a dynamic identity, chaos theory can have a unique<br />role in collecting data of these variations. Therefore it is an important and challenging problem in the field of<br />planning and qualitative and quantitative management of Urmia Lake to verify whether the evaporation time<br />series are stochastic or chaotic that is discussed in the present study. In addition to introduction of different<br />utilities of chaos theory, the monthly evaporation amounts of Urmia Lake in the past 40 years have been<br />studied and predicted in the present research. So after calculating the delay time (T=7.5) by using average<br />mutual information method (AMI) and embedding dimension (d=3) by using false nearest neighbor algorithm<br />(FNN), the slope of correlation dimension diagram has been computed. The non-integer amount of the slope<br />(2.47) represents that the system is chaotic. Lyapunov exponent and broad band in Fourier power spectrum<br />are other indexes reported in the present study and their provided results ensures that the system is chaotic.<br />Thus the amount of Urmia Lake evaporation is predictable. Therefore the amount of evaporation in the recent<br />10 years (1997-2007) have been predicted by means of false nearest neighbor algorithm and verified with the<br />observed data. The results agree with the high accuracy of chaos theory predictions so the amount of evaporation<br />of the Lake is predicted for 10 following years (2007-2017).</p>