After years of stop-and-go talks, California and two other states that take water from the lower Colorado River are nearing an agreement on how to share delivery cuts if a formal shortage is declared on the drought-plagued waterway. Under the proposed pact, California — the river’s largest user — would reduce diversions earlier in a shortage than it would if the lower-basin states strictly adhered to a water-rights pecking order. California’s huge river take would drop 4.5% to 8% as the shortage progressed.