[jacket3ree]

Regarding reservoir numbers, jacket3ree wrote "With Anderson drained as we do the seismic retrofit, Santa Clara County has lost most of its local supply. Really need San Luis to fill up and support import."

San Luis isn't filling as quickly as I had hoped.  For % of historical levels at the date, San Luis was at these levels on these dates
9/15/22  66%
11/15/22 52%
1/15/23  64%  (Last year at this date, it was 54%)

So San Luis hasn't yet made up for 4 months of usage, and we're still worse off than in September.  Hard to believe, but those are the numbers.
(Yes, the absolute numbers are up, but we've lost ground to the goal.)
Is this because Santa Clara County can't use Anderson and so San Luis was being drained faster than normal?
Or is that 66% somewhat misleading?

The Anderson Dam Seismic Retrofit is scheduled to be completed in 2032.  I believe Anderson Dam could hold roughly 50,000 acre-feet of water.

This is my retirement job.  If I delay retirement.....Anderson's capacity is about 90,000 acre-feet, more than all the other reservoirs in the County combined, but FERC had ordered it held at ever-reducing capacities due to the seismic risk. Right now, it stores zero since FERC ordered it drained to deadpool in 2020. The project - now under way with the first phase diversion tunnel - will restore that capacity.  With it out of the system, the County will replace the locally derived supply with additional import from San Luis (State/Federal) or groundwater. 

FERC - Federal Energy Regulatory Commission is only involved because of a dinky 800kW hydroelectric facility built in the early 1980s. That's barely the capacity of a decent sized standby generator. Would decommissioning that facility first mean FERC leaves the scene. No. No, it would not. I did ask.....I'm good at asking the stupid questions.

[jacket3ree]

Regarding reservoir numbers, jacket3ree wrote "With Anderson drained as we do the seismic retrofit, Santa Clara County has lost most of its local supply. Really need San Luis to fill up and support import."

San Luis isn't filling as quickly as I had hoped.  For % of historical levels at the date, San Luis was at these levels on these dates
9/15/22  66%
11/15/22 52%
1/15/23  64%  (Last year at this date, it was 54%)

So San Luis hasn't yet made up for 4 months of usage, and we're still worse off than in September.  Hard to believe, but those are the numbers.
(Yes, the absolute numbers are up, but we've lost ground to the goal.)
Is this because Santa Clara County can't use Anderson and so San Luis was being drained faster than normal?
Or is that 66% somewhat misleading?

The Anderson Dam Seismic Retrofit is scheduled to be completed in 2032.  I believe Anderson Dam could hold roughly 50,000 acre-feet of water.

This is my retirement job.  If I delay retirement.....Anderson's capacity is about 90,000 acre-feet, more than all the other reservoirs in the County combined, but FERC had ordered it held at ever-reducing capacities due to the seismic risk. Right now, it stores zero since FERC ordered it drained to deadpool in 2020. The project - now under way with the first phase diversion tunnel - will restore that capacity.  With it out of the system, the County will replace the locally derived supply with additional import from San Luis (State/Federal) or groundwater. 

FERC - Federal Energy Regulatory Commission is only involved because of a dinky 800kW hydroelectric facility built in the early 1980s. That's barely the capacity of a decent sized standby generator. Would decommissioning that facility first mean FERC leaves the scene. No. No, it would not. I did ask.....I'm good at asking the stupid questions.

[BostonCard]

Btw, here’s what the Stanford golf course looked like around new years.

[tweet]https://twitter.com/sugolfcourse/status/1609624287769669632?s=61&t=P0L3gtlG0HILRI2KAmjT8Q[/tweet]

BC

[BostonCard]

Btw, here’s what the Stanford golf course looked like around new years.

[tweet]https://twitter.com/sugolfcourse/status/1609624287769669632?s=61&t=P0L3gtlG0HILRI2KAmjT8Q[/tweet]

BC

[82lsju]

"After another week of storms soaked Stanford’s campus, the water in the manmade Lake Lagunita has continued to rise.

On Monday afternoon, the water level measured 14 feet, according to a measuring post in the lake. That level marks an increase of six feet from the level recorded on Jan. 8 by The Daily."

https://stanforddaily.com/2023/01/17/lev...w-heights/

[82lsju]

"After another week of storms soaked Stanford’s campus, the water in the manmade Lake Lagunita has continued to rise.

On Monday afternoon, the water level measured 14 feet, according to a measuring post in the lake. That level marks an increase of six feet from the level recorded on Jan. 8 by The Daily."

https://stanforddaily.com/2023/01/17/lev...w-heights/

[81alum]

I biked and hiked around the Lake today.  It is high enough that it cuts off the use-trail on the Junipero-Serra side.  It seems well down from the top of the embankments, though.  With the sun out today and a few fleecy clouds reflected in the water, it was lovely.  I wish I knew how to post photos here without having to link a url.

There was an old sign I stopped to read and photograph.  "USE OF LAKE LAGUNITA.  Lake Lagunita is no longer maintained for recreational use.  It currently functions as a flood control facilty and serves as breeding habitat for the California Tiger Salamander....."

So my memory about flood control was not entirely in error.  I wonder in what sense it is used for flood control, given that we know from our resident expert that it certainly isn't part of the regional flood control plan.

[81alum]

I biked and hiked around the Lake today.  It is high enough that it cuts off the use-trail on the Junipero-Serra side.  It seems well down from the top of the embankments, though.  With the sun out today and a few fleecy clouds reflected in the water, it was lovely.  I wish I knew how to post photos here without having to link a url.

There was an old sign I stopped to read and photograph.  "USE OF LAKE LAGUNITA.  Lake Lagunita is no longer maintained for recreational use.  It currently functions as a flood control facilty and serves as breeding habitat for the California Tiger Salamander....."

So my memory about flood control was not entirely in error.  I wonder in what sense it is used for flood control, given that we know from our resident expert that it certainly isn't part of the regional flood control plan.

[Goose]

So my memory about flood control was not entirely in error.  I wonder in what sense it is used for flood control, given that we know from our resident expert that it certainly isn't part of the regional flood control plan.

Well, all that water in the lake would presumably flowed down the hill and into the rest of the campus area, by Skilling etc. down Lomita Mall. Whether there is enough drainage in that area to handle it I don't know. However, I do believe that the "flood control" function is a serendipity of it being there already. Probably didn't figure much in the "original" planning.

[Goose]

So my memory about flood control was not entirely in error.  I wonder in what sense it is used for flood control, given that we know from our resident expert that it certainly isn't part of the regional flood control plan.

Well, all that water in the lake would presumably flowed down the hill and into the rest of the campus area, by Skilling etc. down Lomita Mall. Whether there is enough drainage in that area to handle it I don't know. However, I do believe that the "flood control" function is a serendipity of it being there already. Probably didn't figure much in the "original" planning.

[81alum]

So my memory about flood control was not entirely in error.  I wonder in what sense it is used for flood control, given that we know from our resident expert that it certainly isn't part of the regional flood control plan.

Well, all that water in the lake would presumably flowed down the hill and into the rest of the campus area, by Skilling etc. down Lomita Mall. Whether there is enough drainage in that area to handle it I don't know. However, I do believe that the "flood control" function is a serendipity of it being there already. Probably didn't figure much in the "original" planning.

Yes, I thought about that.  Here is the real question about flood control and Lake Lag:  what happens if the Lake overflows?  Is there a way the water gets diverted back to the creek?  Are there pumps or an overflow channel?  For that matter, are the embankments behind Roble in good enough shape to contain a really full Lake?  Or are they assuming that there never could be a winter wet enough to overfill the lake?

[81alum]

So my memory about flood control was not entirely in error.  I wonder in what sense it is used for flood control, given that we know from our resident expert that it certainly isn't part of the regional flood control plan.

Well, all that water in the lake would presumably flowed down the hill and into the rest of the campus area, by Skilling etc. down Lomita Mall. Whether there is enough drainage in that area to handle it I don't know. However, I do believe that the "flood control" function is a serendipity of it being there already. Probably didn't figure much in the "original" planning.

Yes, I thought about that.  Here is the real question about flood control and Lake Lag:  what happens if the Lake overflows?  Is there a way the water gets diverted back to the creek?  Are there pumps or an overflow channel?  For that matter, are the embankments behind Roble in good enough shape to contain a really full Lake?  Or are they assuming that there never could be a winter wet enough to overfill the lake?

[CompSci87]

Coincidentally, I took a walk around Lake Lag today too. Had to detour all the way around the outside of the driving range to get past the flooded area. The lake was a pretty sight at sundown with the lights reflecting off it.

[CompSci87]

Coincidentally, I took a walk around Lake Lag today too. Had to detour all the way around the outside of the driving range to get past the flooded area. The lake was a pretty sight at sundown with the lights reflecting off it.

[Mick]

I'm not getting anywhere near that lake...feels like New Orleans to me...

[Mick]

I'm not getting anywhere near that lake...feels like New Orleans to me...

[82lsju]

According to Stanford ecology experts, debris, parasites, water-born pathogens and dead rodents may inhabit Lake Lagunita’s murky water, affirming previous warnings from the University advising students not to enter the lake. While the University only cautioned students against potential “debris, bacteria and deep mud,” experts said other contaminants may plague Lake Lagunita’s turbid waters. 

https://stanforddaily.com/2023/01/17/dro...l-hazards/

[82lsju]

According to Stanford ecology experts, debris, parasites, water-born pathogens and dead rodents may inhabit Lake Lagunita’s murky water, affirming previous warnings from the University advising students not to enter the lake. While the University only cautioned students against potential “debris, bacteria and deep mud,” experts said other contaminants may plague Lake Lagunita’s turbid waters. 

https://stanforddaily.com/2023/01/17/dro...l-hazards/

[CompSci87]

Yeah, I wasn't going to go in the water!

[CompSci87]

Yeah, I wasn't going to go in the water!

[81alum]

That Daily article talked about dozens of dead gophers.  Gopher tunnels are a major factor in the failure of levees and embankments.  Perhaps the lake is not high enough to threaten those levees, but one would think that the University should take a long hard look at their condition before any more stress is placed on them.

https://damfailures.org/lessons-learned/...l-impacts/

[81alum]

That Daily article talked about dozens of dead gophers.  Gopher tunnels are a major factor in the failure of levees and embankments.  Perhaps the lake is not high enough to threaten those levees, but one would think that the University should take a long hard look at their condition before any more stress is placed on them.

https://damfailures.org/lessons-learned/...l-impacts/

[jacket3ree]

I may be the "resident expert" referred to above.*

I haven't looked at Stanford's storm drain master plan in a long time, but it wasn't that long ago that we prepared a regional flood hazard study complete with mapping. Lake Lag was part of the watershed modeling, because we modeled Stanford's system, but nothing stuck out about it in terms of hazard reduction. So, I pulled up Stanford's Detention Master Plan (Nolte, 2001) to see what I could learn/remember/misremember about Stanford's storm drain system and Lake Lag's role therein.

Storm Drainage Detention Master Plan

"A significant drainage feature on the southwestern side of the study area is Lake Lagunita.
The hills generally drain toward Lake Lagunita. The location and drainage area is
specifically noted in Figure 4-1. A storm drain, the Junipero Serra Foothills Storm Drain,
has recently been designed to augment the existing Gerona Ditch to collect flows from the
hills south of Lake Lagunita. The arm of the lake, extending to the west, intercepts flows
from the hills southwest of the lake. Initial flows from very large storm events that
exceed the storage capacity of Lake Lagunita are released by the spillway, and are
captured by a storm drain that is routed to San Francisquito Creek. Flows from the
spillway that exceed the storm drain capacity flow overland across the Campus
northeasterly toward Matadero Creek."


There is natural drainage to Lake Lagunita, so it is storing stormwater runoff that would otherwise run through campus.  I was incorrect - while it was created in the 19th century to hold irrigation water, it does serve a natural drainage control function.  I do not know if anyone has modeled flows with the facility removed to calculate its benefit. It has a spillway (or did in 2001) and if those spilled flows are not captured by a storm drain to San Francisquito Creek, they find their way across campus.  The other lake "outlet" of course is percolation through its sandy bottom, assuming there isn't a layer of silt at the lake bottom preventing that. Right now, the lake level is probably close to local groundwater levels, which are high. My house is barfing water between foundation and adjacent driveway, but it's clear (yea!) and no signs of uplift.  Might be burning up some more sump pumps this spring.  I've gone swimming down below before.....

Someone asked about what happens if the embankment fails. Ans: with a full lake and catastrophic failure; wall 'o water. However, Lake Lagunita is a California Jurisdictional Dam, so the Division of Safety of Dams performs regular inspections. If they felt the embankment is unsafe, they would make Stanford retrofit the facility or remove it completely.  

California Jurisdictional Dams

*On the advice of my professional liability insurance broker, I am not an expert. I am a professional engineer exercising that degree of care and skill ordinarily exercised under similar circumstances by members of its profession performing the kind of services herein and practicing in the same or similar locality at the same time.

(TLDR: I'm just another know-it-all yahoo on the internet, so the bar for y'all to come after me is super low high.)

[jacket3ree]

I may be the "resident expert" referred to above.*

I haven't looked at Stanford's storm drain master plan in a long time, but it wasn't that long ago that we prepared a regional flood hazard study complete with mapping. Lake Lag was part of the watershed modeling, because we modeled Stanford's system, but nothing stuck out about it in terms of hazard reduction. So, I pulled up Stanford's Detention Master Plan (Nolte, 2001) to see what I could learn/remember/misremember about Stanford's storm drain system and Lake Lag's role therein.

Storm Drainage Detention Master Plan

"A significant drainage feature on the southwestern side of the study area is Lake Lagunita.
The hills generally drain toward Lake Lagunita. The location and drainage area is
specifically noted in Figure 4-1. A storm drain, the Junipero Serra Foothills Storm Drain,
has recently been designed to augment the existing Gerona Ditch to collect flows from the
hills south of Lake Lagunita. The arm of the lake, extending to the west, intercepts flows
from the hills southwest of the lake. Initial flows from very large storm events that
exceed the storage capacity of Lake Lagunita are released by the spillway, and are
captured by a storm drain that is routed to San Francisquito Creek. Flows from the
spillway that exceed the storm drain capacity flow overland across the Campus
northeasterly toward Matadero Creek."


There is natural drainage to Lake Lagunita, so it is storing stormwater runoff that would otherwise run through campus.  I was incorrect - while it was created in the 19th century to hold irrigation water, it does serve a natural drainage control function.  I do not know if anyone has modeled flows with the facility removed to calculate its benefit. It has a spillway (or did in 2001) and if those spilled flows are not captured by a storm drain to San Francisquito Creek, they find their way across campus.  The other lake "outlet" of course is percolation through its sandy bottom, assuming there isn't a layer of silt at the lake bottom preventing that. Right now, the lake level is probably close to local groundwater levels, which are high. My house is barfing water between foundation and adjacent driveway, but it's clear (yea!) and no signs of uplift.  Might be burning up some more sump pumps this spring.  I've gone swimming down below before.....

Someone asked about what happens if the embankment fails. Ans: with a full lake and catastrophic failure; wall 'o water. However, Lake Lagunita is a California Jurisdictional Dam, so the Division of Safety of Dams performs regular inspections. If they felt the embankment is unsafe, they would make Stanford retrofit the facility or remove it completely.  

California Jurisdictional Dams

*On the advice of my professional liability insurance broker, I am not an expert. I am a professional engineer exercising that degree of care and skill ordinarily exercised under similar circumstances by members of its profession performing the kind of services herein and practicing in the same or similar locality at the same time.

(TLDR: I'm just another know-it-all yahoo on the internet, so the bar for y'all to come after me is super low high.)

[81alum]

Jacketree, you are a gem!  I am fascinated by the info you dug up.   Next time I walk around the lake I will look for spillway and storm drain.  Is the spillway at the end of that western finger that parallels Juniper Serra and extends out toward the golf course?

[81alum]

Jacketree, you are a gem!  I am fascinated by the info you dug up.   Next time I walk around the lake I will look for spillway and storm drain.  Is the spillway at the end of that western finger that parallels Juniper Serra and extends out toward the golf course?

[BostonCard]

There is natural drainage to Lake Lagunita, so it is storing stormwater runoff that would otherwise run through campus.  I was incorrect -...

Wait!  This is an internet message board.  I thought that sort of thing is supposed to be against the rules or some such thing, because this might be the first time someone has written those words.

BC

[BostonCard]

There is natural drainage to Lake Lagunita, so it is storing stormwater runoff that would otherwise run through campus.  I was incorrect -...

Wait!  This is an internet message board.  I thought that sort of thing is supposed to be against the rules or some such thing, because this might be the first time someone has written those words.

BC

[PAsportsfan]

Click on the link to view a "dry" lake. At the edge of the water, near the "water level gauge/pole" past the orange raft, you can see two brick "formations". Is that part of a drain?


https://www.google.com/maps/@37.422786,-...4352?hl=en

[PAsportsfan]

Click on the link to view a "dry" lake. At the edge of the water, near the "water level gauge/pole" past the orange raft, you can see two brick "formations". Is that part of a drain?


https://www.google.com/maps/@37.422786,-...4352?hl=en

[Mick]

RESSW.pdf (ca.gov)

I've been monitoring water levels on the CDEC site for over 10 years.  I started doing this when I noticed the spectacular claims in the media were separated from reality.  

% of Capacity at this time of the year is interesting, but less important than % of Average for this date.  I have added those percentages to Mick's table (shown in red).  Keep in mind that when the snow pack starts to melt the high elevation reservoirs will fill up rapidly and put pressure on the downstream reservoirs.  Folsom, the state's 10 largest reservoir is a good example of this type of reservoir - it is at 404 feet above sea level.  It's purpose is to catch the snow melt and the massive amount of water flowing through the American river to prevent the historical flooding of the Sacramento basin.  Trinity is higher up at 2200 feet.  It is mostly filled with snow melt.  That is why it is at a low level of capacity in early January.

In 2017 the spillways of Oroville Dam failed and almost inundated Oroville.  it cost $1 billion to repair the damage.  In 2017 I started warning people that Oroville was filling up too fast - 3 weeks before the spillway failed.  At the rate Oroville was filling there was no way to release enough water fast enough.  They should have started earlier in the year.   For smaller reservoirs nearing or exceeding capacity is not such a big deal.  They can release a high % of their storage very quickly.  Oroville is a different story.  It is the second largest reservoir in California after Shasta with a capacity of 3.5 million acre fee.  That's 1.152 TRILLION gallons.

I have a fancy excel spreadsheet that I have crafted over the years with colorful conditional logic and macros.  I am quite proud of the output because you can tell at a glance where the system might be in trouble (over/under average and capacity).  I would post an image, but apparently you can't do it on this site.

As of this evening, the top 20 reservoirs were at 47% of Capacity and 81% of Average. My bet is that 100% of average will be exceeded in a few days.

Using threepointer's scale:  % of Average shown in red  after % of Capacity.

Large (1 MM+ AF)
Oroville, 58% / 105%
Shasta, 53% / 84%
Pine Flat, 48% 126%
San Luis, 46% / 67%.
New Melones, 38% / 67%
Trinity, 30% / 48%
Don Pedro, 75% / 108%
New Exchequer/Lake McClure 56% / 122%
Berryessa, 65% / 85%
Almanor, 63% / 102%

Medium (400k - 999k AF)
Folsom, 55% / 126% 
New Bullards, 80% / 125%
Diamond Valley, 61% / 84%
Friant, 83% / 148%
Isabella, 19% / 71%
Camanche, 75% / 124%

Local Reservoirs (and of local interest)
Hetch Hetchy, 81% / 125%
Lexington, 101% / 242% (not a typo)
Stevens Creek, 70% / NA 
Lower Crystal Springs, NA / NA
San Andreas, 93% / 114% 
Uvas, 102% / NA
Clifton Court Forebay, 56%.

[Mick]

RESSW.pdf (ca.gov)

I've been monitoring water levels on the CDEC site for over 10 years.  I started doing this when I noticed the spectacular claims in the media were separated from reality.  

% of Capacity at this time of the year is interesting, but less important than % of Average for this date.  I have added those percentages to Mick's table (shown in red).  Keep in mind that when the snow pack starts to melt the high elevation reservoirs will fill up rapidly and put pressure on the downstream reservoirs.  Folsom, the state's 10 largest reservoir is a good example of this type of reservoir - it is at 404 feet above sea level.  It's purpose is to catch the snow melt and the massive amount of water flowing through the American river to prevent the historical flooding of the Sacramento basin.  Trinity is higher up at 2200 feet.  It is mostly filled with snow melt.  That is why it is at a low level of capacity in early January.

In 2017 the spillways of Oroville Dam failed and almost inundated Oroville.  it cost $1 billion to repair the damage.  In 2017 I started warning people that Oroville was filling up too fast - 3 weeks before the spillway failed.  At the rate Oroville was filling there was no way to release enough water fast enough.  They should have started earlier in the year.   For smaller reservoirs nearing or exceeding capacity is not such a big deal.  They can release a high % of their storage very quickly.  Oroville is a different story.  It is the second largest reservoir in California after Shasta with a capacity of 3.5 million acre fee.  That's 1.152 TRILLION gallons.

I have a fancy excel spreadsheet that I have crafted over the years with colorful conditional logic and macros.  I am quite proud of the output because you can tell at a glance where the system might be in trouble (over/under average and capacity).  I would post an image, but apparently you can't do it on this site.

As of this evening, the top 20 reservoirs were at 47% of Capacity and 81% of Average. My bet is that 100% of average will be exceeded in a few days.

Using threepointer's scale:  % of Average shown in red  after % of Capacity.

Large (1 MM+ AF)
Oroville, 58% / 105%
Shasta, 53% / 84%
Pine Flat, 48% 126%
San Luis, 46% / 67%.
New Melones, 38% / 67%
Trinity, 30% / 48%
Don Pedro, 75% / 108%
New Exchequer/Lake McClure 56% / 122%
Berryessa, 65% / 85%
Almanor, 63% / 102%

Medium (400k - 999k AF)
Folsom, 55% / 126% 
New Bullards, 80% / 125%
Diamond Valley, 61% / 84%
Friant, 83% / 148%
Isabella, 19% / 71%
Camanche, 75% / 124%

Local Reservoirs (and of local interest)
Hetch Hetchy, 81% / 125%
Lexington, 101% / 242% (not a typo)
Stevens Creek, 70% / NA 
Lower Crystal Springs, NA / NA
San Andreas, 93% / 114% 
Uvas, 102% / NA
Clifton Court Forebay, 56%.

[M T]

As of this evening, the top 20 reservoirs were at 47% of Capacity and 81% of Average. My bet is that 100% of average will be exceeded in a few days.

Using threepointer's scale:  % of Average shown in red  after % of Capacity.
Large (1 MM+ AF)
Shasta, 53% / 84%
San Luis, 46% / 67%.
New Melones, 38% / 67%
Trinity, 30% / 48%

Per this site
 looking only at the large reservoirs that are the most short.

Shortfall of Average (acre-feet) 1/17,    Increase in volume in last day,  Days to reach Jan 17 average at that rate
Shasta       440,000   35,144  12.5
San Luis     470,000   22,902  20.5
New Melones  450,000   11,053  40.7
Trinity      775,000    5,684 136.3

Trinity is going to take a long while to get to average. I'm hoping it gets a lot of its water from snow melt.

[M T]

As of this evening, the top 20 reservoirs were at 47% of Capacity and 81% of Average. My bet is that 100% of average will be exceeded in a few days.

Using threepointer's scale:  % of Average shown in red  after % of Capacity.
Large (1 MM+ AF)
Shasta, 53% / 84%
San Luis, 46% / 67%.
New Melones, 38% / 67%
Trinity, 30% / 48%

Per this site
 looking only at the large reservoirs that are the most short.

Shortfall of Average (acre-feet) 1/17,    Increase in volume in last day,  Days to reach Jan 17 average at that rate
Shasta       440,000   35,144  12.5
San Luis     470,000   22,902  20.5
New Melones  450,000   11,053  40.7
Trinity      775,000    5,684 136.3

Trinity is going to take a long while to get to average. I'm hoping it gets a lot of its water from snow melt.

[81alum]

Trinity is going to take a long while to get to average.  I'm hoping it gets a lot of its water from snow melt.

It does.  I backpack in the Trinity Alps.  Because they are further north and closer to the Pacific than the Sierra, they get a much larger amount of precipitation even though they are much lower in elevation.   It is a lot more like Oregon than it is like central California.  There are some permanent snow fields as low as 7000 feet on some northern slopes.  At least, they used to be permanent.

This is a major reason why the bulk of the state's water storage is in our most northerly reservoirs.  That is the part of the state that gets the most moisture.  I've hiked across snow in the Trinity Alps well into July, depending on the year, even though comparable alpine/subalpine territory in the Sierra is 3000-4000 feet higher.

Trinity Dam is an interesting and controversial dam--the Trinity River drains to the Pacific and does not naturally flow to the central valley.  Just a few miles away Shasta Dam is on the Sacramento River that of course does flow to the central valley.  It is a marvel of engineering (and an ecological catastrophe) that Trinity Dam feeds a diversion complex that sent most of the Trinity River through tunnels to the central valley.  This was devastating to the Trinity fisheries and the Yurok people, and many mitigations have since been tried, including building a fish hatchery, requiring minimum stream flows during certain seasons, etc.  As a result, not all the water captured behind Trinity is now usable for drought-relief--some of it is required to keep the Trinity River looking something like a river.

[81alum]

Trinity is going to take a long while to get to average.  I'm hoping it gets a lot of its water from snow melt.

It does.  I backpack in the Trinity Alps.  Because they are further north and closer to the Pacific than the Sierra, they get a much larger amount of precipitation even though they are much lower in elevation.   It is a lot more like Oregon than it is like central California.  There are some permanent snow fields as low as 7000 feet on some northern slopes.  At least, they used to be permanent.

This is a major reason why the bulk of the state's water storage is in our most northerly reservoirs.  That is the part of the state that gets the most moisture.  I've hiked across snow in the Trinity Alps well into July, depending on the year, even though comparable alpine/subalpine territory in the Sierra is 3000-4000 feet higher.

Trinity Dam is an interesting and controversial dam--the Trinity River drains to the Pacific and does not naturally flow to the central valley.  Just a few miles away Shasta Dam is on the Sacramento River that of course does flow to the central valley.  It is a marvel of engineering (and an ecological catastrophe) that Trinity Dam feeds a diversion complex that sent most of the Trinity River through tunnels to the central valley.  This was devastating to the Trinity fisheries and the Yurok people, and many mitigations have since been tried, including building a fish hatchery, requiring minimum stream flows during certain seasons, etc.  As a result, not all the water captured behind Trinity is now usable for drought-relief--some of it is required to keep the Trinity River looking something like a river.

[terry]

This article from 2016 addresses the question of why Trinity takes longer to fill than Shasta:

https://www.sfgate.com/sports/article/Wh...925126.php

According to the Bureau of Reclamation, Shasta is fed about 70 percent by rain from a vast network of watersheds.

Trinity Lake, on the other hand, is fed about 30 percent by rain and 70 percent from snowmelt.

[terry]

This article from 2016 addresses the question of why Trinity takes longer to fill than Shasta:

https://www.sfgate.com/sports/article/Wh...925126.php

According to the Bureau of Reclamation, Shasta is fed about 70 percent by rain from a vast network of watersheds.

Trinity Lake, on the other hand, is fed about 30 percent by rain and 70 percent from snowmelt.

[TonyLima]

Updated my city by city comparison of rainfall.  Click here to see the good news.

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This article from 2016 addresses the question of why Trinity takes longer to fill than Shasta:

https://www.sfgate.com/sports/article/Wh...925126.php

According to the Bureau of Reclamation, Shasta is fed about 70 percent by rain from a vast network of watersheds.

Trinity Lake, on the other hand, is fed about 30 percent by rain and 70 percent from snowmelt.

Did you know that any water storage change that would adversely affect California's "wild and scenic rivers" is prohibited?  Yet another little-known clause in the infamous Prop. 1.  Read it and weep.

[TonyLima]

Updated my city by city comparison of rainfall.  Click here to see the good news.

---

This article from 2016 addresses the question of why Trinity takes longer to fill than Shasta:

https://www.sfgate.com/sports/article/Wh...925126.php

According to the Bureau of Reclamation, Shasta is fed about 70 percent by rain from a vast network of watersheds.

Trinity Lake, on the other hand, is fed about 30 percent by rain and 70 percent from snowmelt.

Did you know that any water storage change that would adversely affect California's "wild and scenic rivers" is prohibited?  Yet another little-known clause in the infamous Prop. 1.  Read it and weep.