THE FUNDAMENTAL QUESTIONS GOVERNING WATER SUSTAINABILITY AND THE HUMAN CONDITION

"Water sustainability" remains nebulous as an intellectual or operational construct. We live in the Anthropocene Epoch of geologic time. Few “natural” ecosystems have been unmodified by humans and it remains difficult to determine how humans synergistically connect with them. Ecologists no longer subscribe to the theoretical framework of ecosystem equilibrium, much as hydrologists now broadly accept “non-stationarity’--that hydrologic systems change continually at all scales because of natural cycles and human intervention. Finally, from a geologic perspective, the percent of life on earth that has not already become extinct is zero, given reasonable rounding. This fact leads to questioning the extent to which extinction of rare and endangered species might actually affect the human condition.

What does water sustainability mean? Does it mean "sustainable for humans and their agricultural crops" or "sustainable for broadly human- modified ecosystems and human needs?" If we wish to sustain such profoundly modified ecosystems, what scientifically defensible benchmarks need be set in a non-stationary world? In the absence of evidence, to what extent must the precautionary principle be used when making decisions regarding conflicts between water use for humans and sustaining ecosystems? To what extent do humans accept the need for large-scale water transfer between hydrologic basins and/or major re-allocation of current water use to meet water needs for both humans and ecosystems? Finally, to what extent should biological and other engineering be used to maximize water use and control pathogens in waters—and who should pay for it?

Any discussion and resolution of water sustainability at the global or national scale needs to address these questions up front, if there will be any hope in solving the pending global water crisis for humans--let alone the disturbed ecosystems to which we now connect. This discussion will be painful at best, crossing profound philosophical, religious, and economic boundaries. Broad compromises will necessarily have to be forged to avoid regional water supply stresses for humans and ecosystems both now and for future generations.