Cities have resource areas from which they draw the raw goods and foodstuffs required for urban living.  Destruction or interdiction of those supplies must adversely affect the ability of the urban area to survive.  Some resources are more vital than others.  For California water is one.  Cut the water and SoCal can't exist for more than a week.  

If the people whose land the California Aqueduct passes have to chose between watering their crops and themselves or letting the water flow on to LA I suspect enough will decide to grab what they can and let LA go hang.  

Even cyberpunks have to drink and, occasionally, take a shower.  ;-)

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre