using bedrock geology info to fish in acidrain areas

[k-bob]

as discussed before, many PA streams are affected by acid rain, and effects vary with bedrock geology (bedrock types have varying ability to neutralize acid). this state map has nice bedrock geology info, zoom out a bit, geology tab upper right:

http://www.gis.dcnr.state.pa.us/maps/index.html

PA has many types of bedrock. A few are known as lower buffering/ bad for fertility & trout (Tuscarora) or higher buffering/good for fertility & trout (Juniata). (Shawangunk is moderate.) For example, if you look at swift run south of penns creek, noted for bad acid rain effects, it is in a Tuscarora bedrock band. Some nearby streams have different geology and may have more bugs and/or salmonoids.

I came across info on the median pH for water from wells in various bedrock types. This is well water pH and not stream pH, but it may have some utility in finding streams w/ more bugs and trout due to higher-buffering bedrock:

Median pH of water from wells by bedrock, Susquehanna basin:

Burgoon 6.4
Pottsville 6.8
Mauch chunk 6.8
Bald eagle 7.0
Catskill 7.1
Huntley 7.1
Bloomsburg 7.4
Juniata 7.4

anyone know of a complete online set of such info? many bedrock types out there. thanks

 

[troutbert]

I've been very interested in this topic for years, but usually when I mention it to other flyfishers I see their eyes glazing over.

We should have a meeting for all people in PA interested in this topic. There might be 5 or 6 of us!

 

[k-bob]

I would like to do that

sure it does sound very geeky I remember reading in the Orvis small stream fly fishing book about studying geology to find trout

I thought that really sounded excessive however now I'm doing it and I see some results

 

[PAgeologist]

You should be able to find some geochemical data on the PA DCNR website for bedrock and also some data on various groundwater aquifers.

Unless the groundwater intersects another lithology which changes it chemically, those pH values should hold relatively true for water discharging from those formations.

You can also look for key words in bedrock descriptions. Silica rich rocks tend not to have much if any buffering (Tuscarora). Anything mentioning calcium rich or calcite, limestones, or dolomite will probably be good at buffering (see about any rock in central PA). Sandstones are a toss up. It typically depends upon their grain composition and cement composition. Shales typically wont - but some are calcareous.

Hopefully that gives you some help or at least gives you some things to think about...

 

[k-bob]

thanks pageologist... that seems like a good idea the descriptions of the bedrock content are readily available... just clicking on the bedrock layer of the dcnr map linked above... calcium calcite dolomite good, silica bad, will apply that info

 

[PAgeologist]

Silica isnt neccesarily bad - its most likely not going to be great.

There are acid producing bedrock types as well, which are bad. Typically anything black or has carbonaceous or pyritic in the description or is located near a coal seam will produce acidic water - mining doesnt have to be involved. Look for iron/sulfur deposits leaching out from any outcrops or red/orange/yellow staining of rocks.

 

[Fishidiot]

PAgeologist,
Please check your PM.

 

[k-bob]

I got the pH numbers for water from wells in various bedrock mentioned in OP from one of these books... some college libraries have them:

Groundwater resources of the Lower Susquehanna River Basin, Pennsylvania / by Taylor, Larry E.
Published 1984

Groundwater resources of the Upper Susquehanna River Basin, Pennsylvania / by Taylor, Larry E.
Published 1984

Groundwater resources of the West Branch Susquehanna River Basin, Pennsylvania /
by Taylor, Larry E. Published 1983

Groundwater resources of the Juniata River basin, Pennsylvania /
Published 1982 Taylor, Larry E

 

[k-bob]

PAG "Silica isnt neccesarily bad - its most likely not going to be great. "

got it, its relative and calcium calcite dolomite may be better than silica

 

[PAgeologist]

Yes. Calcareous formations (carbonate rich, limestone, dolomite) will most likely be better at buffering than silica rich ones.

 

[k-bob]

if you have a fast connection for massive download, those groundwater resources books can be downloaded as souces w54-w58 from page below (there are tables of "median chemical analysis of groundwater by aquifer and physiographic location" that is the ph of water from bedrock types in subregions)

http://www.dcnr.state.pa.us/topogeo/publications/pgspub/water/index.htm

 

[PAgeologist]

Or I can walk across the hall at work and get most of them...

 

[PAgeologist]

Also, check with your local universities - there have probably been some masters and doctorate papers written with loads of data as well. Most likely for your local area.

 

[salmonoid]

troutbert wrote:
I've been very interested in this topic for years, but usually when I mention it to other flyfishers I see their eyes glazing over.

We should have a meeting for all people in PA interested in this topic. There might be 5 or 6 of us!

4 of those 5 or 6 may have commented on this thread

Understanding geology won't help you catch more fish, directly. It will, however, allow you to make better informed decisions on what streams to fish, which puts you in a position to catch more fish. Plus its fascinating stuff when you start to connect the dots and see the influence that geology has on a stream.

It affects streams on a macro scale - entire lithologies contribute to the geochemistry of the water, which may change over the course of a drainage, and a micro scale - certain lithologies may weather in a certain way to produce excellent pool structure, for instance, or a stream may locally exploit a regional joint/fracture system that develops.

There's a lot more to geology than just limestone/freestone.

 

[JeffK]

This is a favorite topic of mine as well. Don't forget the glacial till deposits that make great aquifers - especially if there are limestone outcrops to the north that got ground up and mixed in. Some places in NYS south of the limestone belt along Rte 20 have been limed by the glaciers even though the Catskill Delta bedrock isn't great - but the effect runs out around the NY/PA border.

 

[k-bob]

I looked at the tables for some NEPA regions, and eyeballing the numbers for those areas it looks like Juniata and Clinton VG, Catskill G, Mauch chunk and Pottsville G-, Pocono and Tuscarora low buffering. no magic numbers, but another thing to consider w drainage area and gradient etc in choosing streams to try using maps...

 

[duckfoot]

Sounds like me and PAgeologist had the same professors in college.

Don't forget the all-inclusive suburbia runoff...the bane of our existence. You never know what else might be in a drainage basin if it's within a stream's borders.

 

[k-bob]

Interesting example many of us know: the east branch fishing creek and its tribs, in a SGL just west of Ricketts. Those streams mostly originate in Huntley (pink) and Burgoon (blue) bedrock, which according to the taylor book table for that region, are low in buffering capacity there. Streams just west are in Catskill (yellow) bedrock, which may be better/higher buffering in that area. I know a few streams 'round there with just slightly different headwaters bedrock, and a few more fish than some EBFC tribs. Headwaters geo seems particularly important versus downstream bedrock.

Interesting that acid rain/bedrock geology issues may suppress fish populations miles from a road, and with zero fishing pressure. Still, looking at geology might help me avoid some of those long walks to areas w/o many fish in the future.

 

[duckfoot]

Interesting that Muncy Creek is a Catskill drainage basin.

I would argue that headwater geology matters more important for water pH because the majority of these freestone streams have rain as their primary source. Rain falls onto the long-eroded (via plants and trees) ground and rock, and seeps those acidic qualities into the water.

Bedrock further downstream has much less surface area over a stream's water capacity than does the ground that the rain made first contact.

Groundwater sources (usually come from limestone) are more suited for supporting trout populations.

 

[k-bob]

thanks DF, story here about raven run in anf affected by acid rain in remote location:

http://www.patrout.org/docs/newsletters/patrout_winter2014.pdf?sfvrsn=2