Eagle's Nest visibility

[apitkin]

Just got back from Eagle's Nest. The basin was tannic and the visibility in the cave was some of the worst I've seen. The ballroom and entire upstream was 10-15 feet, with a little patch of 20' at around 1400 feet upstream.

If you're thinking of going this weekend, save yourself the trouble.

Andy

[hhn_caver]

Was the same last weekend as well. Never got around to sending a report...sorry.

[CaloosaCaver]

Thanks for the Dive report. My dive partner and I have been considering it, so we are going to wait till after the rainy season ends.

[ssmdive]

Wow, on the 6th the viz (upstream to the super-room/ballroom) was fantastic.

[CaloosaCaver]

The first time I dove EN was in the "winter" dry season. Vis was not bad, much further than the HID Video light could illuminate, but as we started down the cone that primary light failed. It was short but the dive was nice.

[apitkin]

The visibility at EN is hard to predict, but there are a few trends that emerge over several years. In general visibility is better in the summer, particularly after a dry spell. It is also affected by the tides, being better at times of lower tidal variation (neap tides) than higher (spring tides). However, there is a lot of scatter around these trends.

My personal theory is that anything that increases the amount of surface water syphoning into the system will worsen visibility. Cold surface water (in the winter) doesn't tend to float on top of the warmer aquifer water, hence the worse visibility in the winter. When there is more of it after heavy summer rainfall it will still tend to get in, despite being warmer. The hydrostatic pressure changes caused by large (spring) tides tends to allow more surface runoff to seep in.

Just a theory. If anyone knows a lot about statistical modelling, we could try putting these environmental factors into a multivariate regression model and see if anything shakes out.

Andy

[loquat149]

If anyone knows a lot about statistical modelling, we could try putting these environmental factors into a multivariate regression model and see if anything shakes out.
Andy

Finally, someone needs a multivariate statistician slash cave diver!! I could help with a quantitative approach, if empirical data are available. Otherwise, a hydrographer might provide a better qualitative, conceptual model. At any rate, it would be fun to install some Hobo temps and a pressure sensor in the Nest and collect observational data from visibility reports. These could then be combined with some of the regional environmental data archived by the various management agencies, etc.

Anyone have a Minnus they could donate to the cause???

Dave

[Walter Pickel]

The visibility at EN is hard to predict, but there are a few trends that emerge over several years. In general visibility is better in the summer, particularly after a dry spell. It is also affected by the tides, being better at times of lower tidal variation (neap tides) than higher (spring tides). However, there is a lot of scatter around these trends.

Andy, one of the interesting thing about having 6 years worth of condition reports is I can generally see how long systems take to clear after floods, how tides and rain affect systems, etc. It is anecdotal but interesting nonetheless. I was using some of the Google visualization API tools to chart this as version one of Cave Atlas but it just seemed now novel than helpful. In the case of the Nest, there are 247 conditions reports since 8.10.2005

[CaloosaCaver]

We did some modeling somewhat like this in Physical Oceanography. I just don't have access to that program anymore. Dissolved material is effected by rainfall and hydrologic pressures of tidal influence. Water column turbidity I think is the primary factor, measured as a function of solution saturation. Water samples with dates, and time for reference to local conditions will be most important.

[apitkin]

Andy, one of the interesting thing about having 6 years worth of condition reports is I can generally see how long systems take to clear after floods, how tides and rain affect systems, etc. It is anecdotal but interesting nonetheless. I was using some of the Google visualization API tools to chart this as version one of Cave Atlas but it just seemed now novel than helpful. In the case of the Nest, there are 247 conditions reports since 8.10.2005

Actually, I was thinking that those hundreds of conditions reports would be the empirical data we could use. Collate those with tidal, rainfall, and other environmental data such as mean daily temperature and see what happens. Is there any correlation, positive or negative, with output from local springs (e.g. Weeki)? It's all available. Then you can make a hypothesis (e.g. 2 weeks of heavy rain in the summer trashes the viz) and then test it against the historical data.

It might even be possible to build a mathematical model that will predict visibility there within certain confidence intervals.