Rain, Irrigation and Declines in GMD 4

One would hope that irrigation, precipitation and groundwater level changes are all relational - the more it rains, the less we irrigate and the slower the water level decline goes.  The following are data for the 10 Counties in NW Kansas for the years 2000 through 2012.  

Col 1 = Year; Col 2 = Annual average precip (10 stations); Col 3 = Reported water use (GMD 4 total, all uses except domestic); Col 4 = Acres reported irrigated; Col 5 = Inches of water reported applied per reported acre irrigated; and Col 6 = January 1 (following year) water level change.  Unfortunately, 2012 data for water use and acres irrigated are not yet available.

The water level change data come from 275 observation wells across the entire GMD area that are measured each January. 

Year  Precip     Wtr Use      Ac Irr      In/Ac      WL Chg 2000   16.72      497,737      386,055        1.29      -1.16 2001   19.79      424,223      380,152        1.12      -0.41 2002   11.30      527,661      386,350        1.37      -1.51 2003   14.06      484,311      386,979        1.25      -1.14 2004   20.13      479,461      385,161        1.24      -0.6 2005   21.15      397,666      381,202        1.04      -0.57 2006   19.37      435,017      379,479        1.15      -0.29 2007   17.07      417,848      377,010        1.11      -0.89 2008   21.65      406,801      377,691        1.08      -0.42 2009   25.59      301,350      376,254        0.80        0.1 2010   17.45      368,030      376,969        0.98      -0.5 2011   22.48      435,900      380,667        1.15      -0.59 2012   11.76      -1.39
I see a pretty strong correlation (inverse) between rainfall and annual declines - Col 2 and Col 6.  When the rainfall increases, the water level decline rate decreases.  Just eyeballing the numbers, it appears to me that with average annual rainfall (18.35 inches) we'd expect about a .6 foot decline.  With 23-24 inches of rainfall, a .25 foot decline, and with 12-15 inches somewhere around a 1.5 foot decline. I see a little less correlation between the reported water use and the water level change, but there is still some relationship.  It is quite true in the extremes, anyway - the wettest year (2009) saw the least water used and the smallest water level change while the driest year (2002) saw the greatest water use and the largest water level change. Most can probably see the inherent sense of all this, but may wonder why there is not a perfect relationship between rainfall, pumpage and declines.  Well there are a number of reasons why we'll never see such an absolute relationship:
1)  The rainfall data provided is annual precipitation.  Six months out of the year the rainfall is far less relevant to crops and irrigation.  There is probably a more relevant relationship between in-season rainfall and what we're trying to show, but this is hard to flesh out when our region gets just 60-65% of its total rainfall in season. 2)  The rainfall data is highly variable - meaning that while the entire NW Kansas average may have been 20 inches, we easily could have had irrigation areas that only got 14 while other areas got 23.    3)  The quality of rainfall is never known in the data.  You might get 20 inches of annual rain, but if it came in 5 hard rains of 4 inches each over a three hour period, most of it ran off and did not contribute to soil moisture conditions that would allow for reduced irrigation. 4)  Any water level change is a function of natural recharge and pumping withdrawals. While more rain generally means increased recharge (and reduced pumpage) it is not an exact relationship (see reason 3) above). 5)  Cropping is in constant flux and different crops affect withdrawals differently - both the timing and quantity. 6)  A late freeze in the Spring, hail, excessive insect or weed pressures all affect an irrigated crop and the amount of water applied.  It may rain 15 inches, but if a late Spring freeze takes out your corn crop, irrigation is greatly reduced that year. Anyway, I think you get the picture.  But I have to say, all-in-all, there is a pretty good relationship in GMD 4 between rainfall, irrigation use and groundwater declines.  Now, if it'd only rain - at the right time, in the right amount and with the perfect intensity...

The Dilemmas of Local Groundwater Information?

Most of what I do in the arena of information dissemination is geared first and foremost to the folks of NW Kansas.  They simply need all kinds of information to make informed decisions about the groundwater resource we have been given the right to manage.  And I see the internet as an extremely effective way to provide that information - it's available all the time, can be (and in the case of our webpage, is) updated regularly and has links to virtually any water information or data anyone in NW Kansas could possibly need.  Our newsletter goes out 6 times a year to these same folks and often mentions our use of a dedicated website, a weblog and twitter for these primo informational opportunities.

Yet, I marvel at the lack of use our folks make of these sources.  Seems the older generation has the stronger desire to understand groundwater and participate in its management, but are not embracing the electronic venues provided.  The younger folks of course jump all over anything e, but don't yet have the interest in groundwater.  Heck, for all our offerings, I've picked up 2 local twitter followers (neither one of which is active today), no local blog followers and a consistently non-local visitation list to our webpage.  We're getting a fair number of hits to all these items - just not who they were created for.

I guess it's going to take a full generation for this to work any better than it is now - waiting until the current youngsters develop the level of interest in groundwater management that motivates them sufficiently.  And of course anyone is welcome to read for enjoyment or use the information we put up, but since this material is not particularly written for non-local and international folks, I often wonder if they get anything out of any of it. 

Maybe I need to get more sophisticated in the preparation and presentation of the material.  If it was absolutely relevant and snappy enough wouldn't the target readers find it?  Yes, it could all be my fault.  Comments or suggestions will be welcomed.

All The Trends Are Right, But...

I've just updated a suite of data sets I have been keeping for about 30 years on GMD things - like water appropriated, decline rates, new water rights filed, etc.  While most of the trends are just the way we'd like to see them, the bottom line is that they are not steep enough to make a lot of difference.  I guess the good news is the problems are not getting any worse.  For all these charts, keep in mind that the district was formed in 1976, hired staff in early 1977 and got it's initial management program approved in 1978.

New Water Rights Filed:  This graph shows how quickly we got the excessive trend of new water rights under control.  What you don't see on this graph is that since about 1990 most of the new water rights were very small appropriations compared to before that time, so while we may have approved 4 new rights in 2009 for instance, the total quantity of new appropriations (water) those rights represent is quite small - especially when compared to 4 water rights that were approved in say, 1980.  You also don't see how many water rights are being removed from the system. There is a net reduction in appropriated water rights regardless of the new rights coming on line of late as we'll see below.

Appropriated vs. Pumped Acrefeet:  The fact that appropriated acrefeet are trending downward is good but it is not a steep trend.  Appropriated acrefeet are lost by certifications, abandoned/forfeited water rights or voluntary reductions/closures.  The annually pumped water is highly climate dependent and does bounce around a bit, but the longer term trend is positive (lowering) as well.

Irrigated Acres, Inseason Rainfall, Pumped Acrefeet:  Again, we see the in season rainfall trend line (blue) essentially level while the pumped water trend line (green) trending slightly downward.  This graph also shows the high correlation between in season rainfall and water pumped.  Unfortunately, the cumulative decline line (bottom line) is not reflecting all of the positive trends, albeit slow ones, which we had hoped it would.  It seems to be stuck on its inexorable downward trend.

Several things could be at work here.  Maybe all the trends are in fact short term trends and/or are not really real enough (significant enough) to affect the bottom line.  Maybe there is a lag time and we'll start seeing the positive effects of all these good trends in the near future.  Maybe the aquifer parameters are changing with depth more significantly than the reduced water use is slowing the decline rate.  It is also possible our observation well measurements aren't what they should be - I've covered that  in an earlier post.  And finally, maybe the reductions of pumping have been solely the result of water use efficiency improvements, and the consumptive water use (which is the only cause of changes in aquifer storage) has actually not changed at all.  And just maybe it's all of these things happening simultaneously.  One thing is clear - the decline problem is far more complex than most realize, and really understanding it starts with being able to measure it way better than we can now.

Beware of Groundwater Depletion Predictions

Topic: Pet peeve (if not number 1, pretty high up there) - Predictions of when we'll run out of groundwater.

Let's start in my own back yard - the Kansas High Plains - Ogallala country. The following was printed on February 4, 1979 in one of the state's leading newspapers:

State water experts predict that irrigation will be nothing but a memory in many large areas of west central Kansas in eight to 10 years. They give northwest Kansas about 15 years..

Well, northwest Kansas is my area, and I'm glad to report that irrigation is still here. And most of it is still in west central Kansas, too.  In other words, the 1979 predictions were not at all accurate.  The question is why?   The short answer is that most predictions take an average trend - like annual decline rate - and project it forward.  In 1979 the average decline rate in western Kansas was approaching 2 feet per year.  With only 40 to 80 feet of saturated thickness remaining in west central and northwest Kansas respectively, and irrigation needing about 30 feet of water to continue, the math at that time seemed close to correct.

But, in real situations, the declines reduce well yields, which in turn reduce water diversions, which in turn reduce the decline rates.  The assumption of a straight-line trend is faulty.  Click on the water level chart above to enlarge it.  This chart involves 50 obsevation wells in one County in NW Kansas - Sheridan.  Graphed are the 4 wells of these 50 which show:  the most saturated thickness in 1965; the least saturated thickness in 1965; the most decline - 1965-2008; and the least decline - 1965-2008.  The heavy black plotting is the average saturated thickness of all 50 wells in each year.

Several things are obvious. First, where there was good water in 1965, the wells were pumped hard and declines resulted. Where there was not good water, there was limited use and a relatively stable saturated thickness. Second, the average decline rate is slowing and in fact all the graph lines are converging toward that average.  Again, the straight line trend assumption if used in this case in 1975 would have been very wrong.

And furthermore, this is just one section of our district. Looking at the same chart for the 19 observation wells in western Grahan County (the next county east of Sheridan) the decline problem is a non-issue.

Water table declines will always be problematic, but they will rarely be as bad as the press and headline grabbers want them to appear.  So, ask the right questions and get the good data before assuming the end of the groundwater world as we know it today.  Groundwater is very temporal and site specific, so generalizations do no one any good.

Saturated Thickness Variability

I'm often asked:  "What's the water table doing?"  It's a perfectly good question, but a difficult one to answer as succinctly as asked - especially in our area where the variability of conditions - from rainfall to actual measured declines - is so variable.  And averages only seem to confuse the issue, so I try to stay away from them. 

Case in point:  our water level elevation data from Thomas County - the heart of our GMD area.  The graph below shows four of the sixty-seven wells measured every Janauary to describe both the water table elevations and the saturated thickness.  (Click on the graph to enlarge it)  The wells are measured to the nearest 1/100th of a foot.  These 4 are the observation wells with:  the most saturated thickness (ST) in 1965; the least ST in 1965; showing the most decline (1965-2008); and showing the least decline (1965-2008).  I have also included (heavy black line) the annual average of all 67 wells.

From these 4 wells we start to see the variability within 1 County - not only in saturated thickness (from 62 feet to 175 feet) but in decline rates as well (from 5 feet to 38 feet).  And if you think spouting average values is misleading (or at least less than helpful) try answering with ranges of values.  Even less helpful to most.  And I've not even gotten into the variability over time, which finds our decline rates at any location changing from decade to decade - due mostly to longer term precipitation variability.

It wouldn't be so bad if it was just water level data, but it's other data as well.  The variability of our rainfall numbers for example stagger even the most hardened meteorologist.  So is the life of a groundwater manager.  Maybe I take it all too seriously.  Maybe people are asking me the rhetorical, ice-breaker question and really aren't that interested anyway.  And maybe that's why I keep all this stuff on our web page - so you can conclude your own answers. 

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.