Credit the drought for allowing the area south of Manteca that has flooded 11 times since 1929 being sparred from suffering its 12th flood.

The San Joaquin River 30 days ago on Dec. 26 was at 8.13 feet at the Vernalis measurement station just north of the Airport Way bridge.

As of Monday, at 9 p.m., it was at 23.17 feet. That reflects water rising 15.04 feet in 30 days.

It is just under 5 feet of the monitoring stage. That puts it on the radar of the California Office of Emergency Services as it means the river is heading toward potential flooding.

Had New Melones Reservoir not been less than 25 percent fill and had been closer to 60 percent as it was in December of 1991, the series of nine storms that have slammed into the state since last month could have led to a much different outcome.

When other reservoirs were forced to significantly ramp up their releases, New Melones during the first third of the storms was keeping its outflow in the single to low double digits. As of Monday, it was releasing 248 cubic feet per second. That is the equivalent of the volume of 248 basketballs filled with water passing a given point in one second.

At the same time, the drought weakened San Joaquin River had no problem taking what Manteca’s storm drains sent it although the French Camp outlet that South San Joaquin irrigation n District  canals drains into was running at  capacity.

That meant despite virtually a month when not going a day without rain was a rarity, the city’s storm retention basins emptied fairly quickly after holding water.

It also helped that Manteca was sparred cloud bursts.

All of that combined to keep flooding in Manteca limited to areas where sidewalks were covered for several hours when water was rushing to storm drains. Most of the storm damage to Manteca was limited to trees toppling, primarily at the golf course.

The river in the past 30 days went from 8.13 feet to 23.17 feet. And while water levels are still rising based on the United States Geological Survey monitoring station at Vernalis the drop off in storms means river elevation will start dipping somewhat in the coming days.

The river rose 1.91 feet from 12:01 a.m. to 9 p.m. on Monday.

At 23.17 feet, it has a way to go toward the minor flood stage at 29 feet. Moderate flooding occurs at 32 feet and major flooding at 37.3 feet.

The highest record flood stage at Vernalis was on Jan. 5, 1997 at 34.88 feet. Next was Jan. 23, 1966 at 34.55 feet with 32.81 feet on Dec. 9, 1950 being the third highest. The fourth and fifth high marks of 37.7 and 37.2 feet were recorded five days apart in March of 1938.

Between Thursday and Monday, another 2.51 inches of rain fell on Manteca to bring the total since July 1 to 15.27 inches using National Weather Service data.

In a normal weather year, 6.00 inches of rain falls on Manteca between July 1 and Jan. 16.

The current rainfall is 255 percent of normal.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com