Wednesday, March 25, 2020

Matilija Reservoir March 2020

Matilija Reservoir March 17, 2020
It appears that our March rainfall event moved more sediment into Matilija reservoir.   Flows in the upstream delta are currently split so that the remnant reservoir has two inlets, one on each bank.  Last year saw significant deposits at the right bank (background of this photo.)  Here, new deposits are visible on the left bank (in the foreground of the photo).

Matilija Reservoir March 21, 2020
By March 21, the reservoir elevation had been lowered due to Casitas Municipal Water District's operations to release water from Matilija reservoir for downstream diversion at Robles.  This revealed the extent of the sedimentation, and allowed the inlet flows to erode a channel.  Note that although the creek was flowing clear, the reservoir still had suspended sediment lingering from earlier in the week.

The hydrograph below shows the flows recorded at USGS gages just below Matilija Dam (red line 11114495) and downstream at Foster Park (green line 11118500).  The difference between these lines is approximately what is diverted into Lake Casitas (excepting other inflow from North Fork Matilija Creek.)  Note the small peak at Foster Park on March 19 when the operation of Robles diversion was temporarily interrupted for maintenance.





On this blog: Ventura River post-fire sedimentation 2019


USGS Flow gages:
Foster Park:      https://waterdata.usgs.gov/ca/nwis/uv?site_no=11118500
Matilija Creek: https://waterdata.usgs.gov/ca/nwis/uv?site_no=11114495

Casitas Municipal Water District diversions:  https://www.casitaswater.org/your-water/learn-about-diversions