PART 2: The Amargosa River Before it Reaches Death Valley: Two questions:
1. To the south, was there almost a contribution from the three dry lakes and the Mojave River this Winter?
2. To the north, what is the Carson Slough and why does it matter?
Question 1: The answer to question 1 is given by following the Amargosa River upstream from where it flows into Death Valley. This is where the river makes its turn, changing from a southward-flowing river into a northward-flowing river. Before the river reaches the hills in the distance it will make a right turn, meet up with at least one sizable tributary, Salt Creek, and make it into Death Valley proper (technically the Death Valley boundary is between the point where this picture is being taken and the distant hills). It is the tributary that will help us address question 1 first, but we will also come back to this same place to begin addressing question 2 from this same point of departure (where the Amargosa River crosses under California Highway 127).
The most significant tributary into the Amargosa River here is Salt Creek which also flows under California Highway 127, just a couple of miles to the south:
Before it flows under this highway, Salt Creek has picked up flow coming from Silurian Valley to the southeast, which sports Silurian (dry, usually) Lake.
It also is fed by several springs along the way. It flows around the base of the Salt Spring Hills in the background of this picture and drains the valley east and south of these hills, which is Silurian Valley.
On this particular day, just hours after a sizable rainstorm event, the flow headed toward the merge with the Amargosa River was impressive:
I have mentioned Silurian Lake before in my pages on the Amargosa River (click on name-link to go there). It is the third in a series of usually dry lakes, coming after Silver Lake, just north of Baker, California, which in turn comes after Soda Lake, just south of Baker, which in turn is fed by the Mojave River, which flows in wet winter years and after large summer storm events.
During an Ice Age, the Mojave flows through these three lakes (so the theory goes) into the Amargosa River, and thus helps that river fill Death Valley's Lake Manly.
The significant [to me, OK, perhaps not to the world at large] thing that happened this year is that the first two of these lakes actually filled, first the Mojave River filled Soda Lake until it topped and flowed over into Silver Lake. Silver Lake did not overflow into Silurian Lake, however. It isn't an Ice Age. Not yet. But it probably could happen anyway, when there is extraordinay rainfall, as a temporary thing.
Let's take a look at Soda and Silver lakes: first Soda Lake, south of Baker, with its lake bottom at 280 feet above mean sea level (MSL for short). I am taking these photos from a hill at 372 feet MSL:
Looking north from this same hill, I can see Silver Lake beyond the town of Baker, so let's go there next:
Just two weeks before this photo was taken I was alerted by a US Geological Survey scientist to the fact that Soda Lake had actually overflowed into and filled Silver Lake. This was exciting: two of the three dominos had fallen! If only Silver Lake would overflow into Silurian Lake, I thought, I would see something that I did not expect to see in this lifetime. But it took me a while to get there from home in Las Vegas.
It was two weeks later, dragging my mother along on one of our traditional (but greatly expanded) "Sunday sucky rides," that I finally got here to take my own pictures. Silver Lake had lots of water, still, but Soda Lake had receded significantly. Why, I wondered, and my US Geological Survey colleague came to the rescue with an explanation: Soda Lake has its groundwater table at the surface, allowing it to both evaporate and sink into the rock and sediment below quickly, and allowing water to discharge upward from beneath.
Silver Lake would see the same evaporation rate, but it did not allow water to move downward as freely as it moved downward in Soda Lake.
Silver Lake had a deeper water table below it, and water moving down and evaporating back up left its load of clay and caliche at depth, creating a bathtub.
Hence, when it does occasionally receive water, it stays longer than is the case in Soda Lake where there is continual discharge from underground waters to the surface making for a salty, wet ground even when there is no water in the lake to speak of.
So, what does it take to get overflow from Soda Lake into Silver Lake? The two lake bottoms have essentially the same elevation (280 feet MSL in Soda, 273 to 279 feet MSL in Silver) and there is probably only about a five foot rise separating the two lakes. So it doesn't take all that much.
Going from Silver Lake to Silurian Lake seems to involve a water-level rise of less then ten feet, given a llok at very detailed topo maps. But when I walked it and measured it it seemed more like 30 to 50 feet. (See my page on this subject: Baker to Death Valley, revisted. There is a little divide to get from the one basin to the other. But even if that is about a 40 foot high ridge, there is another way to get water from the one basin into the other: seepage.
In the last Silver Lake photo below it looks like there is a small hill impeding the lake at its northern exit point. There may be some northward seepage through this sandy barrier, perhaps at a level not far above the current lake level, according to my US Geological Survey informant, judging from the copious amounts of caliche (carbonates and silicates) in the sands of the northward wash, appropriately called Dry Sand Wash. This suggests that before going over the top, waters penetrate the sandy barrier and come seeping out of the other side, evaporating and leaving their dissolved salts and suspended clays behind.
That is enough for the Soda/Silver/Silurian Lakes tale (until we get back to it in another page).
Let's get back to the mighty (this year) Amargosa River to the north of where we have just been playing in mud and water.
Question 2. To the north, what is the Carson Slough and why does it matter?
Let's go back to where the Amergosa River runs under California Highway 127, and this time look north:
here The river cuts through the low mountains in the photos above. That cut is called Amargosa Canyon (follow link to see part of it).
Going north on the highway to where the river enters this canyon shows there to be a copious flow there too. First we look toward the canyon, now to our south:
Next we look north toward Tecopa and Shoshone, California:
I was curious about just how much of this water was coming out of Amargosa Valley, so hurried north (in the semi-dark, hence the false-color photos).
So, our next stop is around Eagle Mountain, the physical end of the Amargosa Valley. Looking south we see the water leaving and the sunset casting its last rays on clouds:
Next we see the flow with Eagle Mountain in the background:
Finally we look beyond Eagle Mountain and see the flow is going strong:
Finally, against the approaching darkness we race still further north, to just below the state line where the Amargosa River comes under California Highway 127 again. And we see only puddles, but no flow! First we look northward (upstream):
Then we look southward (downstream) with Eagle Mountain on the right:
(Sorry about these two photos, I had to rescue them from a very dark image). By now, it was too late to rush down the road to see where the flow around Eagle Mountain was then coming from, and a look at the satellite image I have used before gives a clear clue: look at the major light colored areas, salt and sand lain down by flowing waters from the north-northeast, the Carson Slough, which drains the Ash Meadows wetlands! That this is indeed the source of the hefty flow out of Amargosa Valley was confirmed to me by my US Geological Survey colleague who is an expert on this flow system.
Throughflow is usually from that Ash Meadows direction, with Carson Slough being the strong white line from Ash Meadows to Eagle Mountain where it feeds the Amargosa River which comes in just northwest of Eagle Mountain. In the satellite image above, you can see that the Amargosa River enters a playa (ground-water discharge-area where the sun evaporates the water and it leaves its salts behind) just to the northwest of Eagle Mountain.
The dark red circles are irrigated plots where alafalfa is growing, and the rusty looking areas in Ash Meadows are natural fgroundwater discharge ares where there is much vegetation and life.
So, now I know. And now you know too.