since its inception in 1960, the swp has required the construction of 21 dams and more than of canals, pipelines and tunnels, although these constitute only a fraction of the facilities originally proposed. as a result, the project has only delivered an average of annually, as compared to total entitlements of . environmental concerns caused by the dry-season removal of water from the sacramento–san joaquin river delta, a sensitive estuary region, have often led to further reductions in water delivery. work continues today to expand the swp's water delivery capacity while finding solutions for the environmental impacts of water diversion.