Sunday, April 5, 2020

March rains

March storm moves over the Ojai Valley. This thunderstorm produced a brief period of hail.

After, a record dry January and February, the rains returned in March.  Perhaps not the "March miracle" of the past, but certainly appreciated given the potential for an otherwise very dry year.  At 13" for the season, Ojai is still way below the 23" average rainfall, but it looks like a wet spring ahead.

28 day Rainfall Map, March 2020

The storm of March 11 delivered almost 5 inches at Old Man Mountain, which typically registers the highest rainfall in the region.  Old Man Mountain lies at the headwaters of Matilija Creek, resulting in quickly rising waters during a downpour.  

24 hour rainfall, March 16, 2020
The hydrograph below shows flows in the river for the month of March at Matilija Creek and Foster Park.  The March 16th rain event resulted in peak flows for the season.

Ventura River above Hwy 150,  5pm
March 16, 2020

Ventura River at Santa Ana bridge,  6pm
March 16, 2020

This short burst of energy in the river moved significant amounts of sand and gravel sized sediment downstream.  In addition to visible deposition in Matilija reservoir, sedimentation was evident at Robles diversion and the reach downstream in the Ventura River Preserve.   Gravel is an important habitat consideration for the endangered steelhead, which lay eggs in "redds", or pockets formed in the gravel.  The effects of the Thomas Fire continue to be evident as the river transports sediment eroded from the mountains downstream, to the benefit of riverine habitat. 

Robles Diversion dam, March 19, 2020
Ventura River downstream of Robles Diversion, gravel bars, March 19, 2020
Ventura River Preserve, March 21, 2020

Ventura River Preserve, April 1, 2020

Flows in the river were also translated into rising groundwater at the Ventura River Water District wells and increased storage in Lake Casitas.

Water Supply, Courtesy of Ventura River Water District
April 1, 2020

At time of writing the watershed is preparing for another potentially significant storm and more rainfall for the week of April 5.

On this blog:
Matilija Reservoir March 2020
Steelhead spawning surveys
Thomas Fire

Ventura County Rainfall map
Casitas Municipal Water District
Ventura River Water District