How to lie with statistics... What a garbage, loaded graph! Let's start our axis at... oh... 1,040ft! That will deceive everyone into thinking a ***1%*** difference from last year is a big deal.

Atlanta had growth and, much like their abominal road system, their city planners did absolutely nothing to plan for it! This change has almost nothing to do with climate change and almost 100% to do with cooling for the power companies and total lack of water reclamation like a larger reservoir to cope with this. GA gets absurds amount or rainwater, compared to the West coast and captures very little of it. Lanier was created for this very reason - now it's time to sack up and build a larger reservoir.

== author's response follows ===
Are you saying that entering the spring of 2008 with around 15 feet less depth than existed during the springs of the preceding two years is a good thing?

Is not the winter/spring wet season fill-up critical to the summer reserve?

Please restate your concern. So even a "lier" can understand.

"G" is not all that swift. I suspect he will not respond, his kind never do once their stooopidity is rubbed in their face. Love that spell check! :D

It's a stinky graph.

Unless the viewer takes a close look and pays attention to the number on the vertical axis it would appear that Lake Lanier is starting with about 50% as much water as previous years.

You've tried to make 1% look significant.

Bad dog. No Milk Bone for you.
== authors' response follows ===
Stage level measured in feet is not directly correlated with storage volume: e.g. the cross sectional area of the reservoir is "V" shaped. The lower the stage gets the faster the volume is reduced on average.

Another way of stating this is that there are more acre feet stored in a top foot than in a foot 15 feet down.

You also need to consider that the original purpose of Lake Lanier was flood prevention downstream. When it was built in the 1950's Atlanta was only a small portion of what it was now. A reservoir design primarily for drinking water might have a different withdrawal configuration.

Here's some better, more detailed data about historic levels of Lake Lanier and historic drought trends.

http://www.usps-atlanta.org/lakes/lanier.htm#Draught

A sample set of three years is hardly enough to show a trend and all this graphic does is show that the lake level decreased within the past three years.

I don't find the y-axis distortion in this case to be manipulative, but to each his own. In my opinion it's the best way to frame the data for proper readability. Percentage lake level doesn't really hold up either since there is a greater volume of water in every foot higher you go due to sloping terrain.

What's the purpose of "lier"? Correct me if I'm wrong, but it looks like you are trying to make fun of southern accents or make an ad homonym assertion about the credibility of the original poster. Either way, it only makes you look petty.

=== authors' response follows ==
I too am a bad speller.

It's a stinky graph.

Unless the viewer takes a close look and pays attention to the number on the vertical axis it would appear that Lake Lanier is starting with about 50% as much water as previous years.

You've tried to make 1% look significant.

Bad dog. No Milk Bone for you.

take it from a local, 15 feet is a HUGE difference, something like 1/3 of the capacity [ well, the first 15 feet from full pool is around 1/3 capacity]

The graph is a perfectly standard method of showing data. If they had started the vertical axis at zero, then the lines would have been indistinguishable!

As the creator of this graph, I thought I'd chime in.

I started the graph at 1040' simply so people could see the change in the levels. Where should it have started?

- MSL (0')?
- 919' (bottom of the lake)?
- 1035' (start of the "dead pool")?
- Some other level?

"That will deceive everyone into thinking a ***1%*** difference from last year is a big deal."

"You've tried to make 1% look significant."

Even with the 3.57' that the lake has risen since I did the chart, it's still only at about 57% of its capacity (1,464,000 acre-feet now, compared to 2,554,000 acre-feet when full). That means it's low by about 355 billion gallons -- a bit more than the "1%" that the first few comments stated.

"Unless the viewer takes a close look and pays attention to the number on the vertical axis it would appear that Lake Lanier is starting with about 50% as much water as previous years."

Not 50%, but close. Must closer to that than the 1% that you're stating. Wouldn't it have been more deceptive to start the chart at 0' and make it appear to be almost completely full?

I'll be doing this chart every month for a while (here is the one from April 1), so I'm open to suggestions on how to improve the chart for next month. I just want to get the facts out there as clearly as possible.

Mickey

I have to agree, the graph implies the difference is large without making clear if it really is - I learned more reading the comments! Maybe the better y axis would be "consumer days": how many days of water is available for consumers at current average daily consumption levels. Isn't that what's important?

I have to agree, the graph implies the difference is large without making clear if it really is - I learned more reading the comments! Maybe the better y axis would be "consumer days": how many days of water is available for consumers at current average daily consumption levels. Isn't that what's important?

What was missing was this other plot that shows capacity vs height found here:

http://water.sam.usace.army.mil/bufacap.jpg

Given that most lakes are v-shaped showing drops in water level tend to under estimate the change in the volume of water.
And G most readers of TreeHugger can read the axis and don't see it as 50% less.
Bottom line - if you're dependent on water from this lake (and many others like it with similar graphs) it's not a time for complacency - have a go at the politicians; not the people who compile the graphs.

Cool comments all around!

The west has been effected by Climate Change more that elsewhere in the world according to a report ' The West's Changed report' from the Rocky Mountain Climate Organization and the NRDC of March of 2008, as the rest of the world is heating up by 1 degree, the West is 1.7 degrees.

We could handle of lot of our own problems if we in the west had not 'over-subscribed' the water (TreeHugger, in an earlier article, pointed out that Georgia, too, over-subscribed its available water). In the West we call it, "Paper Water" and in those conditions...developments are assured of water for 'X' amount of years.

How would you like to have bought a house in an area that was 'guaranteed' (how in the world do you REALLY do that???) water for 15 years, the house is now 12 years old, you put your life savings into it ....-> and you think the housing bubble is bad????

Also, remember, surface water is NOT the best way to store water over time - especially as the climate heats up - no matter where you are on this planet. BUT, ground storage has its problems too... particularly, if the area had/has industrial developments on the surface above the aquifer .... See through Google, San Gabriel Valley and percholorate.

Reservoirs have yet another problem - sediment buildup after rain storms wash dirt and sand from surrounding rivers, streams, and hillsides, which inevitably decreases the capacity.

Dry areas evaporate the water away in acre feet from the exposed top and rainy areas wash dirt into water body, lowering capacity.

People are complaining because they have to actually read the graph to understand it?? That is ridiculous. It is perfectly fine. The only thing I would add to it is somehow posting the exact numbers for the beginning or the end of each line (like what the exact numbers are at years end. OR perhaps at low and high points.

As for the graph, a zero type number can be put at the junction of the x and y just for its symbolism, and then make a break line showing the jump.... However, this is a standard type graph and perfectly fine to illustrate changes in depth. What you could do as Bob Wallace suggested, instead of depth, use acre feet of loss. The amount of acre feet would be even more graphic because of the shape of the reservoir.

Atlanta is terrible. I hope the state lines don't get redrawn where Georgia has access to the Tennessee River. You'll hear the complaining from me in Alabama from Atlanta.

It seems that some people do not understand that all lakes are measured compared to sea level.

The bottom of the lake is not at sea level. Its probably at 1,000 feet above sea level or so. Showing the top of the graph is not misleading to anyone that knows how to read lake level graphs. Showing the bottom 1,000 feet would indicate the dirt under the lake.

It is a very telling graph and some people are going to be in big trouble this summer.

Maybe the graph needs to be much simpler for some to understand it. Maybe a graph of the lake depth instead of the lake level wouldn't cause so much confusion for some.

The graph as is is fine. Do people know what AMSL means? It means Above Mean Sea Level. Obviously the lake bottom in the middle of Georgia doesn't extend to the level of the ocean.

The purpose of the graph is to show that after a severe drought, the lake has a long way to go if it were to catch up. Another dry year like last year... and Atlantians thought it couldn't get any worse?!

The surface area, elevation or depth of a reservoir, by themselves, are of little value in assessing the seriousness of a drought. A more meaningful statistic is how many thousands of acre-feet of water are stored and how that number compares to when the reservoir is "full pool" (at a normal/safe maximum level).

In conjunction with this data, it would be helpful to know how many acre-feet of water are taken from the reservoir in a typical day (depending on the season), so that residents can get an idea of how many days worth of capacity remain (assuming a continuing drought) until the reservoir reaches a "dead pool" (the depth at which water intake pipes begin to suck air).

Be mindful that as a reservoir approaches a dead pool level, the water quality usually degrades rapidly, requiring greater filtering/treatment. Dead pool is different from the absolute bottom of a reservoir, since you would not want to use the water near the bottom except under extreme circumstances.

See this example of a graphic for Lake Travis (near Austin, TX):

http://www.twdb.state.tx.us/publications/reports/waterconditions/conservationstorage/plothtm/LakeTravis.htm