The water is higher than we need and the snowpack threatens

The Sierra snow pack continues to go up and the rain keeps on coming. But what goes up must come down. If it comes down too much or too fast, problems we're already seeing could get worse.

Even without rain, aggravating river flows most California rivers are now at very high levels and more rain is on the way. But it's that massive snow pack that is creating a real worry for water experts.

The San Joaquin County Sheriff's Office issued evacuation orders for two neighborhoods in Manteca and Lathrop. Many folks saw no reason to leave since this is an expected event every five to seven years. "Our houses are built for flooding. So, nobody lives downstairs. Like I told you earlier, only two inches in my bottom floor," said Airport Circle resident Mel Sparks.

But Airport Court in Manteca and Haven Acres Mobile Home Park in Lathrop are seeing flooding that might well be a precursor to a much bigger event when the Sierra snow pack starts melting in earnest. Experts say, the hazardous San Joaquin River water level is due to melting lower level snow, forcing swollen reservoirs to make early large releases. "Basically, they're having to get rid of water to make room for the giant snow pack that is to come this spring," said National Oceanographic and Atmospheric Administration and National Weather Service River Forecast Center Hydrologist.

One way or another that snow mass will melt, maybe too rapidly with warm rains and warm temperatures and spring springing. It could cause levee failures that cold especially disrupt agriculture over much of the state. This is especially true in the southern Sierra, which has the biggest snow pack.

There, a massive lake could appear if the snow melts too fast and where evacuations are currently under way with the apparently intentional breach of a levee. But once that's repaired, the snow mass above some of the nation's best farmland will run down three major rivers and seriously threaten it and people who work it. "And so it's gonna be hard to melt that off in a way that's manageable I think. I don't see how they're gonna get around not being able to put water in there. It has nowhere else to go," said hydrologist Haynes.

MORE: Sierra region bracing for snow and flooding

Back in Manteca, residents are mindful of what the Central Sierra snow pack could bring them, but they are not freaked out. "If we thought at all that we would be in danger and we know that the water is just gonna come up real quick, we're ready to go, said Sparks. 

Flooded farmland could amount to a huge supply chain disruption that could affect food prices throughout California and the nation.