A magazine, USNWR, says that 22 (T)rillion US$ will be spent worldwide on water projects at uh, some length of time. I figure saving 20 to 70 pct of that is pretty plausible from an engineering perspective (also is larger than the entire US 2001 GDP value) Thus
less crummy irrigation ditches that
Irrigation ditches that are lined work betterer, yet the ones I frequently see are lined with about an inch of cement, this cracks as well as (presumably) has fairly brief intervals between repairs, thus a cheap irrigation ditch that resists cracking would be of benefit.
Visualize laying cheap metal mesh at an angle \ \ \ \ \ \ \ \ this prevents cracking.
a polymer version similar to the layered safety windshield might also work. The idea being that earthquakes, vehicles, as well as subsidence even if they crack an area merely stretch the polymer preventing drainage
Im aware this idea looks kind of stupid, yet it comes from my actual walking along fairly recently made irrigation structures around the Western US. The technological sophistication of irrigation has tremendous opportunity to be improved.
(More .5bish would be like little biodegradeable floating thingies that washed up "ashore" along irrigation pathways diagnosing where cracks were. Perhaps they could be wildly fluorescent at nonhuman spectra so aircraft could find the locations. )