in the early 1970s, the swp system still had a lot of "surplus" – water supply developed through the construction of oroville dam, which was running unused to the pacific ocean because the water delivery infrastructure for southern california had not yet been completed (and when it was, southern california was slow to use the water). the surplus water was given for irrigation in the san joaquin valley instead. because the water would only be a temporary supply, farmers were advised to use it for seasonal crops (such as alfalfa or hay) rather than permanent crops such as orchards. nevertheless, many farmers used the water to develop new permanent crops, creating a dependency on swp water that is technically part of southern california's entitlement, this is now causing tensions as southern california continues to increase its use of swp water, decreasing the amount of surplus available to the system, especially in years of drought.