Reality in hydrologic systems: Changing challenges into opportunities

Hydrologists spend much of their time studying virtual hydrologic worlds where things are simple. Our science has evolved to favor simple hydrologic worlds for several reasons, most of them quite logical and justifiable. First and fundamentally, there is a methodological belief that by studying simple replicas we can discover instructive lessons applicable to real worlds. Second, the dominance of models means that our ideas of reality are often shaped by the capabilities of digital models of the day. Finally in a more practical sense, technological limitations and costs constrain the ability to collect data, to continuously monitor complicated geochemical systems, to synthesize detailed information about large, regional systems, and to keep track and access terabytes to petabytes of data/information.  However, if these simple ideas or interpretive models are poor representations of reality, what have we learned?  If real systems defy study and analysis, who then will address the critical real-world problems? We use an example of nitrate fate and transport in the Upper Scioto River of Ohio to illustrate a system where complexity is manifested by local differences magnified by scale. Complications arise because of the inability to characterize the uncertain details of the hydrologic settings and to account for a variety of influences related to the types and extents of anthropogenic modifications to the water resources systems (field tiles, impoundments and reservoirs) and the complexity of contaminant loadings in space and time. Work on real systems is frustrated by process complexity, too many variables, unresolved and uncertain parameters, and information gaps that cannot be plugged. These challenges should lead to unprecedented opportunities for those willing to understand the important advantages in studying such real worlds.