More on Water Levels

Kansas maintains an observation well network that it measures each year to track changes in the water level depths across the state in its major aquifers.  The annual measurements vary, usually between 1,200 and 1,500 wells, based on how many wells can be accessed each year, but a solid attempt is made to return to the same wells each year.  The 2012 measurements were taken from 1,327 wells, for example.

The statewide average change in water levels between January, 2011 and January, 2012 was a 2.28' decline.  The overall range was from a 13.63' rise to a 23.68' decline.  Keep in mind that 2011 was a very dry year for the southern half of Kansas.

An interesting look at the January, 2012 data (January, 2011 to January, 2012 change) is by GMD.  The GMDs in Kansas do not cover the entire state, but do cover 85% of the groundwater producing areas.

  GMD 1 (West Central):  1.58' decline (range: 4.85' rise to 15.57' decline)
  GMD 2 (South Central):  3.12' decline (range:  2.91' rise to 11.67' decline)
  GMD 3 (Southwest):  4.05' decline (range:  13.63' rise to 23.68' decline)
  GMD 4 (Northwest):  .57' decline (range:  4.6' rise to 5.48' decline)
  GMD 5 (South Central):  2.96' decline (range:  5.28' rise to 9.72' decline)

While I'd like GMD 4 management programs to take full credit for the state's lowest (by far) average decline rate in 2011, the truth is that our area had way more rainfall than the other areas.  We were still below average (a bit on the dry side) but not near as dry as the other GMDs.

Another way to look at the relative impacts might be to focus on the lone Index wells for each of the western GMDs.  From the 2011 calendar year pumpage, our GMD 4 (Thomas County) Index well dropped 6.69' - from a recovered level of 212.40' on March 17, 2011 to a low of 219.09' on September 4, 2011.

As of August 5, 2012, this same well has dropped 6.95' - from a recovered level of 213.70' on April 27, 2012 to a new low of 220.65' on August 5.  And the irrigation season might have another 3 weeks to go, so we expect additional declines to come.

All this to say that the GMD 4 average annual decline rate of somewhere around .5' per year may get blown out of the water this drought year of 2012.

Groundwater Levels - Thomas County Index Well

This is the graph starting on June 17, 2008 of the Thomas County Index well.  This well has a data logger installed that collects a water level measurement every hour and uplinks that measurement to the Kansas Geological Survey.  The index well is a dedicated monitoring well that sits about 1/2 mile away from any operating wells.  I've blogged about this program before, so if interested, check out the other articles - generally under the "Index Wells" or "Thomas County Index Well" labels (right side of blog page).

The point I'd like to make today is on the right side of the graph.  The last reading shown happens to be 219.78 feet below land surface on July 26, 2012, and represents the lowest level this well has ever been since monitoring began and until today as this post is being written.  I know 4 years is not much of a data set, but the fact that this level has been achieved as early as July 26 is telling.  All the previous lows were reached in late August or early September - just as irrigation was concluding for the year.  Immediately following irrigation season the water levels always begin their dramatic rise and return toward recovery - until the next irrigation season begins.  This being the pattern, it appears that this year's low is going to go significantly lower yet as irrigation season likely has at least another 3-4 weeks to go.  

Another telling fact is that 10 water rights have been retired in the general area of this index well over the past 4 years through the state's Water Transition and Assistance Program (WTAP) - within 8 or 9 miles of this index well.  These retirements total just over 1,000 AF of irrigation water that had been pumped annually but are no longer being withdrawn.  Had these 10 water rights been also competing for this region's groundwater this year, it's likely the groundwater level on July 26 would have been even lower.

You can look at this data anyway you want to, but clearly it represents some degree of a problem at some time in the future.  Should you chalk it up to the extreme drought and argue that things will look much better when normal weather returns?; or, Should you start thinking about slowing the decline rate in the hopes of extending the economic life of the groundwater supply?

That brings me back to the Local Enhanced Management Area (LEMA) process.  This index well sits very close to the middle of the TH-5 High Priority Area - one of the 6 designated enhanced management areas of GMD 4.  This area held stakeholder meetings back in late 2008 and early 2009 on addressing their declines, but haven't yet sustained enough momentum to go any further.  Perhaps this is the data that might get them more interested and involved.

Trouble for the Taj - Water Woes to Blame

Taj Mahal, Agra, India

I added an entry in my "movies including wells" listing a while back on a Smithsonian Channel documentary on the famed Taj Mahal, in Agra, India.  It's well-related factoid is that basically the entire foundation of the tomb-part of the structure was built on a grid of groundwater wells dug and filled with material for adequate support.

There is now much angst within India over the structural problems of the iconic Taj Mahal since the adjacent Yamuna River is far over-used, polluted, and drying up along with local groundwater levels dropping far too quickly - reported at 5 feet per year in the immediate vicinity.  It is the dropping groundwater levels that are drying out the 358+-year old mahogany piles used inside the lattice of wells to support the structure.  In the drying out process these posts become brittle and start to disintegrate.  Recent reports claim cracks have appeared in the tomb over the past year and that the 4 minarets are showing signs of excessive tilting - a structural collapse looming, according to some, in as few as 5 years.  A group has been set up to deal with the preservation, but claim a lack of funding is why nothing has been done since 2003.

They must have known something was afoot all along, because according to the Smithsonian Channel, one of the foundation wells was left open purposely for an observation well.  A 350-some year old record of on-site water levels should be a pretty good data set I'd think.  Groundwater declines always seem to be a problem - first it's land subsidence, drying up of wells and water supplies, loss of wetlands, river baseflows and deep rooted flora.  Now it's dessication of monument foundations. 

Here's hoping the government can solve this problem.  The Taj Majal is indeed in the top 3 list of the most architecturally beautiful buildings in the world - ever. 

Predicting Full Aquifer Recovery

Trying to understand the aquifer recovery process following a pumping season for irrigation has led to some interesting things.  First, the rate of recovery is not constant, but increases as time goes by - at least in the unconfined aquifer conditions we have here.  Secondly, there are 2 distinct stages of aquifer recovery - the first being the initial 1000 hours (41 days) and the second being everything afterwards.  Thirdly, our aquifer never recovers fully before the following year's pumpage begins to drop it again.

With data loggers in a dedicated index well taking water level measurements every 2 hours since the Summer of 2007, we have data on four full recovery stages and three full pumping stages.  (See data and graphical results here)  The data has been plotted both as a semi-log recovery curve and as a Horner recovery curve - for each recovery year.  All the plots show a distinct, 2-stage recovery process.  Here is a Powerpoint update with many of the graphs and data sets.

What is so amazing is that the theoretical full recovery (as predicted by the Horner plots) will take a full year or more to happen.  This finding has implications on the true accuracy of the annual well measurements Kansas has been collecting since the mid-1940s.  This was a surprising find.

The graph included (click to enlarge) shows the projected full recovery levels for each of the three captured recovery periods as red dots.  For ease of understanding they have been assigned to the same dates as the highest physical recovery even though these recovery levels would not be achieved for another 6 months to a year. The yellow dots are the annually measured (official water levels) for this well for all four years.  Using the annual measurements, we think this well's 2010 water level was at 2974.5'.  Using the 2010 theoretical recovery level (following the 2009 pumping season) the water level would be 2978.9' - a difference of 4.4 feet.

Discerning what the water level is for any data point is simply not all that easy and straightforward.

But what is straight forward is voting on my poll.  So go ahead, do it!

Groundwater Monitoring

I need help with the science of groundwater monitoring. Our existing observation well network consists of 287 (or so) wells that are spacially located across the district via a 6.25 mile hexagonal grid.  Statistical work said this spacing and configuration would give us an acceptable accuracy to describe the water table attitude with the least number of wells to be measured. 

Subsequent statistical analysis confirms that the current network is in fact satisfactory enough to determine, over longer time frames, the areas of the district where water level changes are relatively worse than, or better than, average.  However, it is NOT sufficient enough to monitor the water levels in smaller areas, or for shorter  time frames - which is what we need now in the designated high priority areas.

How then is the best way to improve the accuracy of these smaller observation well networks?  Is it simply a matter of density?  The pundits tell us that all else being equal and with our variability in our aquifer bedrock, it takes approximately 4 times the well density to double our statistical accuracy.  Do we use data loggers or continue with annual tape measurements?

Would an index well (or two or three) be a better approach?  Theoretically, once the index well is data logged, corrected for barometric influences and has a recovery curve applied so that its full recovery level can be ascertained, just a few of these could more accurately reflect what is actually going on in these smaller areas from year to year - and maybe even one if we choose wisely.  But then we have the issue in the short term of comparing new, corrected and massaged data with the existing unmassaged data.  And the water users are not keen on one index well replacing the 9 obs we currently have in this specific area.

I'd be interested in hearing from the science community on any other approaches that would be available for consideration - preferably other approaches that have worked in other places.