Letter to the editor: If the water level in the Searle River Delta continues to drop, the rising sea level will make the water saltier and less suitable for drinking. Currently, 40 percent of the water from upstream tributaries is diverted to neighboring areas. To keep the delta's water level from dropping any further, we should end all current diversions from the upstream tributaries. Neighboring water utilities are likely to see higher costs and diminished water supplies, but these costs are necessary to preserve the delta.
Which of the following would, if true, indicate a serious potential weakness of the suggested plan of action?