The tiny, remote dot in northeastern San Diego County known as Borrego Springs and its several thousand residents face a daunting task: To survive, they need to ensure they use the same amount of water as the town has in its sole aquifer, which provides declining supplies. Officials expect to have 75 percent less water available by 2040, and they say the town must allow most of its 3,800 acres of citrus and other farms — which use 70 percent to 80 percent of all the community’s groundwater — to fallow. The narrowly defeated Proposition 3, the $8.8 billion state water bond, would have provided $35 million to fallow the farms, which would then become part of adjacent Anza-Borrego Desert State Park. Now there’s talk of pursuing a new water bond or seeking help from the Legislature to fallow farms and retrain about 60 farm workers for other jobs.