 Large-scale irrigated agriculture was introduced to the Central Valley in the late 19th century, and led to the construction of numerous state, federal and privately owned dams. Water demand has often been higher than the river's environment can sustain. Salmon have been blocked from migrating and riverside habitat has declined dramatically. Recent years have seen habitat conservation work, mimicking of historic streamflow patterns, and the establishment of a salmon hatchery, in the hopes that the river's health can be protected from further damage.
