Almost everywhere gets there water from some other area (even groundwater), which is why the concept of a “water supply chain” will come of importance. More spe

Almost everywhere gets there water from some other area (even groundwater), which is why the concept of a “water supply chain” will come of importance. More specifically, “area” can be defined as the point sources for utility water distribution lines. As another poster mentioned, watershed is the common term. I’m not sure what point you are trying to make beyond water flowing downhill. My point was, if I’m a lender, and I’m about to lend to a property that has a history of water shortage + a severe threat of total drought, i’m hedging my bet by knocking back the appraisal to be sure I can get my money back from the property given the likelihood of drought. Likewise, I think there is an outsized chance wildfire or an empty fire hydrant, my premiums charged to the property are going way up. In these cases, “area” is looking at all possible options for getting potable water to the site for the foreseeable future, including high cost options like trucking supplies in to refill municipal water supplies.