With members of Congress and the president unable to make a budget deal by late last night, recreation opportunities and services on federal lands will see a sharp decline today.
U.S. Forest Service, Bureau of Reclamation and Yosemite National Park representatives say facilities will be closed and recreational services put on hold during the partial federal government shutdown.
Law enforcement and Rim Fire firefighting efforts and recovery work will continue.
The partial shutdown took effect at midnight, as congressional Republicans refused to drop demands to defund the Affordable Care Act, or Obamacare, which took effect today.
President Barack Obama and Senate Democrats have refuse to accept the Republican budget offerings.
As of this morning, websites for the U.S. Department of Agriculture (which oversees the Forest Service) and Yosemite National Park only displayed a message referring to the government shutdown. The Yosemite website stated that the park is closed.
Shortly before midnight, Budget Director Sylvia Burwell directed federal agencies to "execute plans for an orderly shutdown."
Some 800,000 federal workers facefurloughs. However, some critical government functions - from the military to air traffic controllers - will remain operational.
The interruption in funding sends the federal government into territory unexplored in nearly two decades. In 1995 and again in 1996, budget disagreements between Republican lawmakers and President Bill Clinton resulted in shutdowns.
Stanislaus National Forest spokesman Jerry Snyder said firefighters still working on the smoldering Rim Fire will stay in the field because they are considered "essential" services. A special team formed to jump start the fire recovery process, known as the Burned Area Emergency Recovery team, will also continue working.
The U.S. Forest Service's regional office said only essential activities will remain intact - fire suppression, law enforcement, emergency disaster response, some regulatory activities, cyber security, and some other functions that do not include recreation.
As of this morning, forest officials were still meeting to figure out and announce which employees will be told to go home and which services, amenities and areas of the park will close. Stanislaus National Forest spokeswoman Veronica Garcia referred questions to the USDA's main office, but she did say this morning that they still don't know all the details at the local office.
"No one knows," Garcia said.
In Yosemite National Park, through-roads will remain open, including Highway 120 and its connection to the Tioga Road, for drivers heading over Tioga Pass, park spokeswoman Kari Cobb said. However, all lodging, camping, trails, amenities and recreation activities will be shut down, Cobb said.
Park visitors this morning were given 48 hours to leave the park, Cobb said.
"You'll be able to drive through, but no services will be open," she said.
Similar closures should be expected at New Melones Reservoir, which is managed by the U.S. Bureau of Reclamation. Pete Lucero, bureau spokesman, said camping, picnicking and other recreational facilities at the Tuttletown and Glory Hole recreation areas will be shuttered.
The privately-owned marina could remain open, however, Lucero said boat launches won't be accessible for the public and the front gate will be shut.
Not all federal government functions will cease, however.
The U.S. Postal Service will remain functional and the Social Security Administration should continue to perform some tasks, including some benefits applications, requests for appeals, processing some changes to accounts and others.
As Congress gridlocked, Obama said a "shutdown will have a very real economic impact on real people, right away."
He laid the blame at the feet of House Republicans, whom he accused of seeking to tie government funding to ideological demands, "all to save face after making some impossible promises to the extreme right wing of their party."
House Speaker John Boehner, R-Ohio, responded a short while later on the House floor. "The American people don't want a shutdown and neither do I," he said. Yet, he added, the new health care law "is having a devastating impact. … Something has to be done."
Hours before the possible shutdown, the Senate voted 54-46 to reject the House-passed measure that would have kept the government open but would have delayed implementation of the health care law for a year and permanently repealed a medical device tax that helps finance it.
In response, House Republicans sought different concessions in exchange for allowing the government to remain open. They called for a one-year delay in a requirement in the health care law for individuals to purchase coverage. The same measure also would require members of Congress and their aides as well as the president, vice president and the administration's political appointees to bear the full cost of their own coverage by barring the government from making the customary employer contribution.
"This is a matter of funding the government and providing fairness to the American people," said Boehner. "Why wouldn't members of Congress vote for it?"
The vote was 228-201, with a dozen Republicans opposed and nine Democrats in favor.
Unimpressed, Senate Democrats swatted it on a 54-46 party line vote about an hour later.
Obama followed up his public remarks with phone calls to Boehner and the three other top leaders of Congress, telling Republicans he would continue to oppose attempts to delay or cut federal financing of the health care law.
The impact of a shutdown would be felt unevenly.
Some critical services such as patrolling the borders and inspecting meat would continue. Social Security benefits would be sent, and the Medicare and Medicaid health care programs for the elderly and poor would continue to pay doctors and hospitals. VA clinics will remain open.
U.S. troops were shielded from any damage to their wallets when Obama signed legislation assuring the military would be paid in the in the event of a shutdown.
The Associated Press contributed to this report.