Dam construction on the Colorado River that began in the 1930s and lasted for four decades severely reduced-and frequently cut off altogether-flow into the Colorado River Delta. Today the delta is much reduced from its pre-dam size, but remains an ecological oasis rich in biodiversity, aided by increased river flow in recent decades. Management decisions made now will determine its future. Feature articles look at the changes in streamflow and habitat over the decades, water quality, water management, and cross-border and grass-roots restoration activities in the delta.