One of the big questions staring me in the face is... as we reach the limits of sustainable use without “significant harm” to the environment and reuse more and more wastewater, what happens to the systems that have adapted to the volume of discharge provided by our waste stream outfalls?As all of you know, I am not a scientist, and therefore unqualified to comment on the size of the impacts from these changes in use, but I wrote this back:
We have looked at many issues to determine if there is extra available water in our basins, but the amount of “freeboard” available for additional human use may be equivalent to the volume projected to go into reuse -- purple pipe systems here -- in the future.
Reuse is fantastic for farmers recapturing and reusing fertilizer runoff, cities looking for less regulated water sources for esthetic irrigation, and water quality improvements in general. It is terrible for salinity intrusion up rivers with lower discharge volumes, groundwater recharge areas fighting salinity intrusion, hydroperiods in flat wetlands, migratory species looking for a critical water depth, and other water volume dependent issues.
Have you looked at that?
Also variability in the demand for water reuse is a big issue. Spray fields used to help discharge extra water exceeding reuse storage volume, almost always occurs on rainy days or after the soils are saturated. That is when lawns don’t need to be watered and spray fields are least effective at handling the runoff. It seems to be when reuse water managers run the spray field pumps 24-7. What is your experience with the expense of reuse water storage?
I agree with your general points, that (1) "efficiency" may leave nothing for nature (eg, the Jordan River) and (2) human centric changes may tip systems into collapse.Can any scientists comment on the these issues? Can any policy wonks give examples of where science feedback is driving policy reform?
But those dangers are often ignored by humans. My "end of abundance" thesis is that we've exceeded limits that we've been able to ignore for ages.
What are our choices, now that we're seeing the impacts of our behavior? We can either step back and rethink our habits or drive ahead and off the cliff.
It seems you've described the manifestations of failure to reform. The question is whether policy "leaders" will act on those bad outcomes
(The EU's Water Framework Directive is an attempt to improve environmental water quality and quantity, but it's top-down and resisted by many national governments.)