Alnitak
Member
- Joined
- Jan 6, 2014
- Messages
- 314
Given the spread of age classes and the total number of streams, its much more than just rainfall/snowfall. I'd guess its a wide variety of factors:
1) Reduced agricultural runoff. Not just from buffer zones, but in general just better agricultural practices, better education, better regulation. You can see the long-term trends across the basin at the USGS site for the Chesapeake Bay: http://cbrim.er.usgs.gov/maps/index.html
2) Decreased atmospheric deposition of pollutants and specifically acid rain. The 1990 Clean Air Act amendments in particular led to a fairly steep decline in the following decade. In PA average rainfall pH values in many locations was about 4.5 in the early and mid-1990's but by 2010 it was typically 5.5-6.5. That's a HUGE difference for breeding success for trout, especially in freestone streams with low buffering capacity.
3) Buffer zones on headwaters. There's a LOT more of this than there used to be. I left here 20 years ago and it was a rare sight back then. Now many of the fields I go to have fences up to keep the cattle out of the water and buffer zones with small trees. A ton more could be done here, but its amazing how much has already been done. This plays a key role not only in reducing non-point-source pollution but also in keeping water temperatures cooler for longer periods of time.
4) Small stream dam removal. This is another long-term trend where public opinion has helped shift things in favor of the coldwater migratory fishes. More and more of the small stream dams are being torn down as time passes by.
Jeff
1) Reduced agricultural runoff. Not just from buffer zones, but in general just better agricultural practices, better education, better regulation. You can see the long-term trends across the basin at the USGS site for the Chesapeake Bay: http://cbrim.er.usgs.gov/maps/index.html
2) Decreased atmospheric deposition of pollutants and specifically acid rain. The 1990 Clean Air Act amendments in particular led to a fairly steep decline in the following decade. In PA average rainfall pH values in many locations was about 4.5 in the early and mid-1990's but by 2010 it was typically 5.5-6.5. That's a HUGE difference for breeding success for trout, especially in freestone streams with low buffering capacity.
3) Buffer zones on headwaters. There's a LOT more of this than there used to be. I left here 20 years ago and it was a rare sight back then. Now many of the fields I go to have fences up to keep the cattle out of the water and buffer zones with small trees. A ton more could be done here, but its amazing how much has already been done. This plays a key role not only in reducing non-point-source pollution but also in keeping water temperatures cooler for longer periods of time.
4) Small stream dam removal. This is another long-term trend where public opinion has helped shift things in favor of the coldwater migratory fishes. More and more of the small stream dams are being torn down as time passes by.
Jeff
