"I am moving to another house - the yard is bigger, so i will build a 15 x 23 pond with a 2 foot wide, 45' long stream. To me, this seems extremely small for a frog pond, but not for fish. I think this is much to small for more then like 10 mature green frogs and a few small ones."
My pond is about 10x x 15' and has a good frog population but not more than 10. My smaller ponds actually attract more frogs since they're fishless.
"the reason i describe this is because i want to know if you think thats enough area to release toads, leapard, pickerel, green, and wood frogs. The reason i think wood frogs might do well is because of all the bushes, rock piles, and the english ivy that they can hide in (area of 60 x 15)"
Wood frogs need mature forest. All the debris and ground cover in the world won't replace that. They may hang around at first if you release some but will probably tend to wander off. The other frogs you mentioned will probably hang around more especially the green frogs who live near water all year.
"the big question is with that pond - how many mature green frogs would be pushing it - since, its really on the green frogs that are territorial at the water's edge? pond: 15 x 23. i was real dissapointed at the small size when i layed out sticks in a 15 x 23 circle."
That's not that small a pond. It's bigger than mine anyway. Don't worry about how many it can support. Just get a few at first, and let nature take care of the rest. I have probably 10-30 adult green frogs and hundreds of tadpoles at any one time in my various ponds all together. They are not as territorial as bullfrogs. Mine seem to get along pretty well. Two males may not want to sit next to each other for too long but I've had up to half a dozen mature adults lined up around my 153 gallon pond on a warm spring day.
"I would really like to make a small vernal pond, like the ones you described.
I have a few ideas:
a. I can divert the stream's flow into a seperate shallow pond (very very minimal flow) and then have a second stream to allow the water to pass out of the vernal pond - i can only have it flowing in spring and summer and then i can cut off flow to grow bog plants only once the frogs mature."
That might work if you can get the plumbing right. Remember though that part of the definition of a vernal pond situation is no water flow at all. You may in fact want to cut off the flow to that small pond from late winter into spring to allow the tree frogs, wood frogs, etc. to use it and then turn the flow on after the tadpoles have matured in mid-summer. Even if they did lay eggs in there, with flow, the tadpoles would probably wash down into the main pond where they'd be eaten.
"The reason i want to have some flow in and out is to prevent stagnation, to have the mosquito larvae to flow into the real pond so they can be consumed, and so that i can flush out any remaining animals in late summer."
The tree frogs LIKE stagnation. The more yucky, the happier they are! Mosquito larvae love it too. Some tadpoles eat mosquito larvae. I just use mosquito dunks in my stagnant tub ponds where the frogs lay eggs. The tadpoles seem fine and when they get bigger, the mosquito numbers decrease. I may get bitten once or twice a year by mosquitoes. The dragonflies and bats get some of the adults. My mosquito page is
http://www.fishpondinfo.com/mosquito.htm"However, i fear that i cannot fill it with leaves and let it stagnate if its going to be flowing back into the pond - because ill be adding nutrients and excess protein/waste to the pond - unless i only fill it with water plants like mill weed and elodea."
A small stagnant section that flows into the main pond would yuck up the main pond a bit. But with that flow, it wouldn't be all that stagnant.
"b. If i made it a stagnant vernal pond, i worry about mosquitos and dont want to use fish or tablets.... would a ton of elodia work - cause its known to prevent 30%? mosquitos, i think."
Elodea or anacharis won't stop mosquitoes. There's a liquid form of Bt bacteria now like the mosquito dunks so you could try that. It's more expensive but you don't see it. Also, the floating plant azolla is also called mosquito fern because it blocks the surface off so mosquito larvae can't breathe. Of course, that also means the tadpoles can't breathe so well either.
"I don't know what to do - id love to just use a 20 x 20 liner and make a 10" deep vernal pond - but im sure ill have mosquito problems."
See my mosquito page. Like I said, the mosquito problem in my yard is such that I get a few bites a year is all. I do use the mosquito dunks but often still see wrigglers. There are many animals that will come to the ponds to help eat mosquitoes.