The thinking started small and then grew much bigger at a gathering Tuesday in Bakersfield that was intended to provide a “survival toolkit” for farmers and water managers facing drastic restrictions on Central Valley groundwater pumping. Irrigation and other technical specialists opened the meeting by promoting ways to maximize the region’s existing water resources. Discussions ranged from individual investments in desalination to gathering water-use data as a way for farmers to defend against government accusations of over-pumping.