As I recall, the watershed for Lake Tahoe is actually very small, because the surrounding ridges are quite close to the lake. The surface of the lake is the majority of the total collection area for precipitation.

To me, this suggests that evaporative losses may also be a significant portion of the draw-down you see each year, i.e. precipitation and evaporation on the same surface area. A trend towards more rapid reductions in water level may say something about climate shift, with hotter and drier summer conditions?

Perhaps also reduction of watershed area because of development and capturing of waste water? I know there are mitigation efforts around the usual farm and garden runoff (nitrogen etc.) for Tahoe; lack of such mitigation why Clear Lake[0] is a soupy green.

[0] https://en.wikipedia.org/wiki/Clear_Lake_(California)

Yes, but probably due to increasing development and population increases... It's to be expected, as the region wasn't meant to support all the new people and companies watering their new lawns, cooling data centers, and people taking baths and washing their Ferraris.

Climate change is indeed real, but exaggeration about it's effects only drives profit up, fear often creates apathy and fatigue, rather than encouraging positive change in identifying and adjusting the root causes of the issue.

I expect you're being downvoted because agricultural irrigation is the primary use of water, not residential water use. Residential water use makes up a relatively paltry fraction of total use compared to agricultural.

How much Lake Tahoe water (or feed water) is used for agriculture?

Can't speak for tahoe, but here in Utah, I read that total residential water use accounts for about 2% of the total water use of the state, and individual households it's something like 0.02% ... so really it's like comparing an ounce of piss to the ocean.

Alfalfa farms (of which the governor is an alfalfa farmer) are the worse culprits as it's a water heavy plant, and we're also a top exporter of alfalfa to Asia, so essentially Asia's buying our water from us via alfalfa.. there's plenty of other corporate/industrial culprits, but farms are a huge one here..

I'm specifically asking about Tahoe. Down in the valley below, California uses a LOT of water for agriculture, no question. But I'm not sure ag-use is an issue for Tahoe water.

I ask because it's a high alpine lake surrounded by mountains. It has no significant water outflow. I'm not sure there's a path for water from the lake's watershed into agricultural land. Water is lost from the lake to evaporation in enormous amounts and to local uses in much smaller but probably still significant amounts, and that might be about it.

But OP argues that overpopulation leads to increased water usage. Farming takes more water as more people it has to feed.

The statement was a pretty obvious insertion of humor to lighten the mood. I'll eat the downvotes because I don't want to be serious in a world that believes in punishing people for trying to have a sense of humor. :P