Downie Lake is a 3 1/2 hour drive from Albany, and a 20 minute somewhat steep downhill hike from the trailhead parking area. (I should say 20 adult minutes. With Coltrane, it took 40 minutes down and an hour coming back up.)
Downie Lake is in the "Grouse Lakes Vehicle Control Area," part of Tahoe National Forest and is proposed for wilderness designation. You can get a free map in .pdf format here. When you look at the map you'll notice that Downie Lake is just one of numerous lakes in the area, and for being so close and easy to get to, it isn't especially popular or well known. The most popular hike in the Grouse Ridge area is probably the 5 lakes basin, or the hike to Glacier Lake.
Downie lake is good for swimming, and the fishing is suppose to be good as well. According to gorp.com Downie Lake "receives little use because the lake is not on a trail. Rainbows are planted every two years. Some trout reach 22 inches."
The trailhead parking area is 73 miles northeast of Sacramento on I-80, a few miles past Blue Canyon. From I-80, take the westbound State Highway 20 exit, and after about 4 miles, turn right where a sign points to Bowman Lake. After about 6 miles on the paved road to Bowman lake, turn right on the dirt road signed "Grouse Ridge Lookout." It took me about 1/2 hour to drive the 6 miles of rough, dirt road to the trail head. While there are several juntions, some unsigned, on the dirt road, just keep going straight on the most obvious and well used dirt road. The trailhead parking is just past the Grouse Ridge Campground.
While no trail is shown on the map to Downie Lake, there is an unsigned and unmaintained "use" trail. It leaves the Grouse Ridge trail to the right at this sign.
Even though the trail is unmaintained, it's not too hard to follow. It's mostly loose rock, and follows a drainage to the lake.
When the trail reaches the lake, you'll find a nice campsite on the right. Great views, but it was pretty dusty. It didn't take long for the three of us to become completely coated. There are a couple other campsites very close by.
Here we are on the rocks above the campsite. On the Sunday and Monday when we were here, there was no one else at the lake, or even at the other smaller lakes around.
If you continue hiking past the campsite, you find the dam that forms Downie Lake. Just 10 minutes beyond the dam is this smaller lake that also has a couple nice campsites. Andrea thought this one was nicer than the main lake. On some maps, Downie Lake is shown as Downie "Lakes", since there are several other smaller lakes around it.
Another view of the lake below the dam. You can see that the bottom of the lake is rocky, and a bit mucky as well. I was comfortable swimming, but some people might be more comfortable with water shoes. As you leave the shoreline, the lake gets too deep to stand up in.
If you continue above the lake below the dam, there are two more. This one was very dramatic, but I didn't see any campsites.
This pond is to the left of Downie Lake as you approach from the trail. It has a couple nice wooded campsites, but the mosquitos were a problem when we visited.