Karr, J. R. (1991).  Biological integrity: A long-neglected aspect of water 
resource management. Ecological Applications.  1:66-84.
	
Water of sufficient quality and quantity is critical to all life. Increasing 
human population and growth of technology require human society to devote more 
and more attention to protection of adequate supplies of water. Although 
perception of biological degradation stimulated current state and federal 
legislation on the quality of water resources, that biological focus was lost in 
the search for easily measured physical and chemical surrogates. The "fishable 
and swimmable" goal of the Water Pollution Control Act of 1972 (PL 92-500) and 
its charge to "restore and maintain" biotic integrity illustrate that law's 
biological underpinning. Further, the need for operational definitions of terms 
like "biological integrity" and "unreasonable degradation" and for ecologically 
sound tools to measure divergence from societal goals have increased interest in 
biological monitoring.