Reliability of Model Forecasting Results

Rehability of final data depends, first, on the correct selection of thermodynamic and chemical laws and their use in hydrogeochemical mathematical models, and second, on the selecting means of its solving and reliability of utilized values. For this reason at the evaluation of final result quality by means of software programs are identified two levels of revision validation and verification. They have the same objective but differ in properties, rules and restrictions. Their violation is considered an error. 

Validation determines not the acctnacy of the received data but only their correspondence with the set objective. Under the standard GOST R ISO 9000-2008, the vaHdation means the confirmation that the 

Verification evaluates the accuracy of received data by the extent of their adequacy with similar data determined in a different way. It may be reliable only in really existing objects by way of comparison of the computation experiment results with observations in the field. Actually, verification includes evaluation forecast results reliability. Whereas validation confirms that the program is correct, verification proves that it may be used for solving the set problem. 

A forecast error is equal to the difference between genuine or real and predicted or forecast values. As in other cases, in its value may be identified two addends correctness, i.e., closeness of the predicted value to the genuine one, and precision as a measure of random errors with equal probability of variance from some medium value. The former ones may be eliminated, the latter ones may only be decreased. 

The forecast correctness may be evaluated only in cases 1) at shortterm forecasting when the pre-emption period has already expired and actual values of parameters have been measured 2) xmder the statistical technique when forecasting is performed based on a time series of regime observations. For this the obtained final data are compared with results of either laboratory experiments with the same processes (for instance, with ionic exchange or dissolution of minerals) or field studies, sometimes with dependably established parameters. 

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