PARAMETER ESTIMATION FOR A GROUNDWATER FLOW AND HEAT TRANSPORT MODEL OF A WETLAND SYSTEM: SELECTION OF TIME SCALES THROUGH FREQUENCY DOMAIN ANALYSIS

摘要

The estimation of model parameters under transient conditions has the potential of revealing important dynamic characteristics of a system and the danger of a prohibitive computational cost. This paper presents the application of frequency domain analysis to select appropriate time scales for the estimation of parameters in a groundwater flow and heat transport model of a wetland system. It was verified, both at the annual cycle and daily cycle levels, that the periodicity in heat transport is clearer than periodicity in groundwater flow. We anticipate that the methodology will have transferability to other temperate wetlands where large annual and daily temperature fluctuations occur. Harmonic analysis of land surface temperature and groundwater temperature data showed that most of the variances are explained in terms of the annual harmonic cycle. That analysis showed a remarkable consistency, at the yearly cycle level, between land surface temperature and groundwater temperature at all depths. Frequency domain analysis for harmonic components higher than the first (or yearly one) showed that the significance of frequency relations decreases as one considers temperature records at deeper depths.