Table 1. — Summary of advantages and disadvantages of various modeling approaches 

 and techniques. 



Approach- 

 Technique 



Advantages 



Disadvantages 



Empirical 

 (Statistical) 



Relatively simple to con- 

 struct. 



Assumes that the same dynamics 



and structure are always operating. 



Gives rapid response to 

 management questions. 



Cannot extrapolate beyond the 

 historical observed field data. 



Mechanistic Can potentially define all 



(Causal) the important processes 



and interactions. 



Increased complexity over the 

 empirical approach. 



Can be used to extrapolate 

 beyond the range of 

 observed field data. 



Formulation and assumptions can 

 predefine results. 



Amenable to experimental 

 and conceptual testing. 



Causal relationships which drive 

 the system must be known and 

 quantifiable. 



Static 



(Time 



Invariant) 



Relatively simple to 

 construct. 



System response easily 

 analyzed. 



First order estimates. 



Potential for inappropriate 

 aggregation of time dependence. 



Gives no information about system 

 behavior with time. 



Cannot be time-stepped with high 

 level of confidence. 



Organizes information on 

 key system components. 



Can be useful in focusing 

 data collection efforts. 



Dynamic 



(Time 



Variant) 



Gives better approximation 

 to real processes. 



Output is often overwhelming and 

 sorting the signal from the noise 

 is difficult. 



Estimates impacts on dif- 

 ferent time scales. 



Requires increased computations 

 over static method. 



Shows potential inter- 

 action between temporal 

 forcing variables. 



Relatively difficult to construct 

 and quantify. 



Relatively large data requirements, 



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