VI-9 

 Meaning 



Each descrifitor is a valiil ineasurG of some system characteristic 



needed for either technical or institutional estuarine manaqemf^nt 



purposes . 



Compatitiil ity 



Each descriptor is cither directly informative or can he conipr^red 

 or combined i/i Ih other di.-scriptors to ho nieaninqfiil . For example, 

 excefit in extreme cases, tid(.> ranne alone is not a useful manaqe- 

 ment statistic; but in combination with the ared of the estuarv, it 

 can help in determininn flushinq characteristics and overall al)ility 

 of the system to rid itself of pollutants. 



Uniqueness 



Each descriptor is a fundamental datum; tl'at is, it cannot be derived 



from other information included in the Inventor/. 



For two reasons, 1950 has been set is an arbitrary cut-off date for 

 mist historical data. First, water quality and waste discharge 

 information, and many kinds of economic data extremely nertinent to 

 the needs of th.is Study, were rarel / collected before that date. 

 Second, ecoloqical and bioloqical cfianqes caused by estuarine altera- 

 tion before that date would scarcely be discernible now, nor could 

 their causes be traced. 



