Amawalk Outlet seems to be in good shape. My understanding is that the problem in the past was sewage treatment effluent entering Hallock's Mill Brook, causing turbidity and siltation in that stream, which empties into Amawalk 1/3 mile below the dam, affecting insect life in the vicinity. This has reportedly been corrected, and does not seem to have a significant effect today, according to the CWCTU book.
We have had a somewhat dry spring so far this year, statistically, but the streams are not terribly low at the moment, since our big rain this week. Perhaps as summer approaches this could become more of a concern, and it would affect some of the smaller streams.
Interestingly, the information about water flow is actually available online, if you do a bit of googling. The DEP website has a map about current reservoir levels, available at
http://nyc.gov/html/dep/html/drinking_water/maplevels_wide.shtml. That page also has a link to the USGS website, which has a phenomenal amount of data available about surface water conditions measured around the country.
For the USGS list of New York surface waters:
http://waterdata.usgs.gov/ny/nwis/current?type=sw&group_key=basin_cd&search_site_no_station_nm=For the Amawalk Outlet flow:
http://waterdata.usgs.gov/ny/nwis/uv/?site_no=01374941&PARAmeter_cd=00065,00060,72020,00062,00010 The current flow is around 19 cubic feet per second, which is a little below median for this date (25). It is around 30th percentile, by my guestimate (for the statistically challenged, that means that the water flow today is higher than 30% of values for this date recorded in the database, or lower than 70% of records). Mean flow is 34; the minimum was reported in 2002 at 9.5, the max for this date in 1997 at 136. These are based on records kept since march 1994. Amawalk tends to have a fairly steady release, compared to many other streams, from what I can see in these data.
Now how's that for answering your question about water conditions at Amawalk?
Unfortunately, returning to your first post in this thread, fly hatch reports would be out of date by the time you read them on this forum, if that is what you meant by "fly activity." Major hatches in small streams often last but a few hours, and are not easily predicted. I came across some website recently that listed the periods of typical hatches for various waters in the region in a gantt chart style, which might be very useful to help one prepare for fishing, to decide what patterns to tie and stick in your fly box. But until you get to the river, there is no easy way to know what is hatching at the moment.
I have caught trout in these streams even when there was not clearly a major hatch occurring and I saw no fish rising. I used nymphs. From some of the things I have read, it appears that the great majority of a trout's diet in small streams is subsurface critters, not hatching flies or spinners on the surface, so nymphing can still catch lots of fish when there is no hatch.
The streams are great places to go for a sense of peace and tranquility, even on days you catch no fish.
And when you can't get out to fish, you can surf the web and learn interesting things about fishing. That's what I mean by doing your homework.

nerding out,
Steve