The Codorus Creek outflow from Lake Marburg near Hanover, Pa., is reliable, but the creek ain't all that big and the lake is massive and deep.
As for Maryland, my home state, I can think of four cold-water release operations. As was mentioned at the beginning, they are fairly well managed, but it could be better. In all four cases, though, trout fishing is pretty much optimal.
Savage River from the Savage River Reservoir: pretty reliable, and a reasonable accommodation allowing for whitewater kayaking as well as trout fishing.
North Branch of the Potomac below Jennings Randolph: Pretty much the same comments as for Savage.
Big Hunting Creek: The creek is small and the lake is small. For years, DNR Fisheries has worked to keep enough flow below the dam to keep the fish healthy through the summer and have enough on hand to boost the flow for the autumn spawn. A lot of guys complain and blame the state park's desire to keep the recreational attributes of the lake going through summer, but the wild trout wouldn't be there if the lake were bled dry before the October-ish spawn. For years, it was the best wild trout stream in Maryland.
Big Gunpowder Falls below Prettyboy Reservoir: For decades after the reservoir was built as a reserve for the Loch Raven, the Gunpowder was maintained as a put-and-take fishery. The reservoir system is owned and operated by the City of Baltimore, which under the Maryland Constitution, is responsible for providing to the City as well as several suburban counties. At least as far back as the early 1970s, organizations like Trout Unlimited and the old Maryland Fly Anglers as well as the fledgling Free State Fly Fishers saw the potential of a cold water release from Prettyboy, but Baltimore City was uninterested in talking about it. Such was the case through the first term of Mayor Don Schaefer, but in his second term he decided he wanted to get some suburban support, so in the early 1980s, he had the city agree to a minimum release. In addition, the agreement included hiring a water works biologist who would have input into how releases would be arranged. This was to preclude massive midsummer floods followed by weeks of nearly dry streambed. This is the period when the Gunpowder blossomed into an important Mid Atlantic trout fishery. The city abided by the agreement for several years, and even did work on Prettyboy dam to improve the functionality of the cold water release valves. In more recent years, though, particularly after the biologist retired and was then not replaced, the city has been very letter-of-the law with regard to the releases. That's why we are back to getting massive floods followed by extended periods of minimal flow. Fortunately, the days of no flow seem to be off the table. It probably makes sense for some of us to revisit lobbying the city's leadership to get some semblance of balance restored to the Gunpowder releases. These days it seems like there are a fair number of us Gunpowder anglers who live and vote in the city limits, so I suspect there's some leverage to be exercised.
