cc  >> Nadia Dominguez: Thank you  for joining me for Wednesday  Nite at the Lab, at the  UW-Madison Biotechnology Center.  Tonight, we welcome Dr. William  Bland, a professor in the  Department of Soil Science  at UW-Madison.  Dr. Bland attended Pennsylvania  State University, where he  received both his BS and MS  in horticulture.  He's been here at UW-Madison for  a while, as he received his PhD  in soil science and horticulture  from UW-Madison.  Currently, his research  interests range from what I just  found out, as of two minutes  ago, are the effects of climate  change on soil erosion to  tonight's topic.  So, two very timely research  interests.  So, tonight's presentation will  review basics of groundwater and  ongoing research to understand  the linkages amongst groundwater  level, conversion of land to  irrigated agriculture and  pumping.  Please join me in welcoming  Dr. William Bland  to Wednesday Nite at the Lab.  (applause)  >> William Bland: Thank you.  I'm looking forward to, over the  next 45 minutes or so, to share  some thinking with you that  we've been doing over the last  year or so, two years, about the  situation with groundwater in  the central sands region around  here. 

 It's right about where Portage  County, Waushara County and  Adams County meet.  Beginning a few years ago,  residents in the area noticed  that lake levels were dropping.  This is a photograph of Long  Lake, right near the Waushara  County border, one of 50 Long  Lakes in Wisconsin.  And you see that there's no  water in it anymore.  Some 90 residences around this  lake that have seen the water  disappear.  So a consolation, if it is any  at all, is that the town, Oasis,  agreed to re-assess their  property values from lakefront  as a result of this.  The photograph on the right is  of the Little Plover River.  Every summer for the last couple  of summers now, stretches of it  have been going dry.  This is a cold water trout  fishery.  It supports trout fish. 

 And so, for fans of nature, and  rivers, and trout, it seems like  photographs like this are very  discouraging.  Well, the timing of our talk  here tonight could hardly be  better.  Today, the Wisconsin Assembly's  Natural Resources committee  began debating, held hearings on  AB844, the Groundwater  Protection Act.  This is a proposal that will, if  put into law, will set the laws  that regulate groundwater use in  Wisconsin for into the future.  Now, this proposed law has been  attracting a lot of interest.  Here's a call from one of the  agricultural groups in the  state, particularly concerned  with the central sands, urging  their members to get down to  Madison today to attend a  hearing and talk to their  legislators.  Here's a similar one that came  out also last Friday from an  environmental group.  Again, urging their members to  attend a hearing and talk to  legislators in support of the  bill.  The agriculture group was against  the bill.  Well, one thing that these  groups do have in common,  though, and they'll all agree  that groundwater is an  incredible resource that we have  here in Wisconsin. 

 I want to discuss the idea of  groundwater, just generally, for  a couple of minutes.  Then we'll talk more  specifically about water  budgets, the kind of tallying  that we have to do to understand  what's happening in a  groundwater resource.  Then I'll show you some research  results, some modeling results  that help us to understand and  think about what are the impacts  of irrigation in that region on  the water resources.  Well, this is a general picture  of the land in Wisconsin, is  that groundwater held in an  aquifer down beneath our feet.  On top of that is a layer of  soil, typically.  And then in between, there'll  often be a transition zone that  has been imaginatively the  intermediate zone.  But not really much happens  there.  So on top of this soil, that  run-off there is called the  ecstatic skin of earth.  And it overlies geological  formations that have water in  tiny pores.  Now, I tell my students, when  talking about this, that I like  to think about a think called  the porosphere. 

 And so, it's another one of the  o-spheres.  The blogosphere, atmosphere and  the biosphere.  I tell them not to bother  anybody else about this word  porosphere, because it's not  really widely used.  But I like to use it, because it  reminds me how much water,  that's very important to us, is  held in tiny little pores, tiny  cracks and voids in the solid  material beneath our feet.  So a nice soil is typically 50%  pore space, part of it filled  with water, part of it filled  with air, typically, in our  soils in Wisconsin.  In contrast, then, down in the  groundwater aquifer, the pores  are all completely filled with  water.  So we call that saturated.  And a geological material that  has good porosity, that's  connected and holds water, has  water in it, we call an aquifer.  Groundwater is held in aquifers.  It's intriguing to me that  depending on where you are,  there may be several different  aquifers underfoot. 

 How many depends on whether  you're a lumper or a splitter.  Lumpers tend to say, well, let's  just count four things.  Splitters worry about all kinds  of subtle differences.  But a lumper's analysis of the  aquifers of Wisconsin shows four  of them here.  The crystalline bedrock that  underlies all of Wisconsin.  Then there's this eastern  dolomite, a little wedge, you  can see right there.  The sandstone and dolomite  aquifer.  This is where, here in Madison,  we get all of our municipal  water from.  Madison is the largest city in  the United States to rely  exclusively on groundwater for  its municipal water supply.  Then as we get up to the central  sands again, this sand and  gravel aquifer, the surficial  sand deposits are the major  aquifers that we'll be concerned  with in this talk. 

 Well, different aquifers have  different characteristics.  They can yield water at  different rates.  So the aquifer that Madison  draws its water from is a  tremendously prolific aquifer.  That's why we get away with it.  We can pump so much from it for  the city of Madison.  And aquifer like the sand and  gravel one here can also be very  prolific and yield a lot of  water.  It's near the surface, more  easily contaminated than a  deeper aquifer, for example.  But there are different  characteristics in how much  water they can supply, and in  the chemical nature of that  water, because the water is  sitting there in the pores in  contact with this geological  material for long periods of  time.  Now, it's really difficult to  see groundwater.  It's hidden beneath our feet in  these tiny little pores. 

 But there are a few surface  manifestations of it that we  occasionally catch glimpses of  it.  Here is, for example, a  photograph from the Spring Green  region, where the last couple of  years, the groundwater levels  have risen up.  Groundwater has made a bid to  become a lake, I guess.  And so, the groundwater table  now is quite high there.  A lot of these homes have been  purchased by the federal  government and are being  dismantled.  Here's a photograph of a large  spring called Big Spring.  Belfont, Pennsylvania.  This is the city where I was  born.  It's a very productive spring.  Here's a wonderful photograph of  a spring in the Pheasant Branch  Watershed. 

 Some of you may have seen this.  It's what geologists call a sand  boil, where you can actually see  the groundwater pushes up and  jostles the sand particles, and  it appears to be boiling and  bubbling up.  Very beautiful.  And then, groundwater also feeds  rivers and streams like this.  That's why these rivers and  streams just keep going and  going and going, even during  periods when it hasn't rained a  lot, or hasn't rained for weeks.  Another surface manifestation of  groundwater are lakes, like the  Long Lake that we're talking  about here.  They form where the groundwater  intersects the land surface,  where for some reason, the land  surface was scooped out and the  water table connects with it.  Here it is schematically.  The groundwater sort of flows  through, but is exposed with  this lake surface.  Here's a photograph from  December 31, 2004, of Long Lake. 

 I think what we're seeing there  is a lot of the bare bottom of  the lake, and then ice and snow  on a bit of the rest of it.  Well, there's another way to see  groundwater.  And that's through a monitoring  well.  Here is the results measurements  from a monitoring well at the  Hancock Agricultural Research  Station.  That's outside of Hancock,  Wisconsin.  It's a research station operated  by the College of Agriculture  and Life Sciences.  So here, the US Geological  Survey has been monitoring the  level of the groundwater at this  point since some time in 1951  when they began measuring it.  And you see, it's got all sorts  of manners of ups and downs.  This is depth of groundwater  from the surface of the soil,  going up and down.  I just checked a little bit  before coming over here. 

 And as of 6:00 tonight, it was  at 14.3 feet  below the water surface.  So it's still right, quite low.  Now, our topic is human  appropriation of groundwater.  So a figure like this leads us  to wonder, what is the effect of  human appropriation on the  observed groundwater levels.  How much of this fluctuation is  due to natural variations in  annual rainfall, for example,  and how much of it is due to  human appropriation, our pumping  out of the groundwater.  I'll take this opportunity to  point out that these two periods  of very low groundwater levels  were in the midst of multi-year  droughts, very low rainfall  periods.  And more recently, though, we  have not had that kind of low  rainfall in the region.  In northwestern Wisconsin, there  has been, for several years,  a continuing drought.  But there's no reason to think  that's affecting our groundwater  in the central sands.  Groundwater doesn't work that  way. 

 Okay, well, one question then,  of human appropriation of  groundwater in the vicinity of  that record that you just saw in  the central sands region.  Here's a map of irrigated area,  agricultural irrigation for  Portage and Waushara County.  And for the line, right here is  the population growth of Portage  County.  So there's been an increase in  human population there.  They rely on groundwater pumped  from a number of wells in  Plover, Whiting, Stevens Point  municipalities.  We see then also, Portage County  continuing, from the 1940s, when  irrigation just started,  continuing to climb just until  very recently, when it stopped  climbing up in total acreage.  So it's a good reason to think  it's clear that we're  appropriating groundwater from  the aquifer there.  You can see here from this image  from Google Earth, all of this  area, here's Waushara County,  Adams, Portage.  Stevens Point is right up in  here.  This is the Wisconsin River and  Interstate 39. 

 All of these spots along here  are agricultural fields that are  all irrigated.  If we look at aerial photographs  from a couple of different  decades, as we've done, and try  to mark out the irrigated lands,  we can see that proliferation of  irrigation wells, here from 1980  to 2005.  This is, of course, reflected in  those statistics that I showed  you earlier.  So we know municipalities and  industry are pumping water out  of this.  Municipal wells and industrial  wells, we generally have the  records on how much they're  pumping.  We know that farm irrigated  acreage is on the increase from  the agricultural statistics, and  on the views that I've just  seen.  So the question here then, is  where's the effect of this level  of groundwater on the springs  and streams and lakes that that  groundwater is feeding?  I told you about some of the  ways that we get to see  groundwater, from the surface  springs, lakes, rivers.  If the groundwater level drops  some, there's a chance that the  groundwater's contribution to  those surface water features can  now be reduced or even go away.  Well, in order to do this, we  will have to develop a water  budget.  Actually, the proposed  Groundwater Act that is  currently being debated at the  legislature, has in it  provisions for defining  groundwater management areas. 

 And one of the things that  they'll do if a groundwater  management area gets defined, is  that they'll begin a public  process to create a water budget  for that area, so the citizens  and politicians of the area can  know where the water is coming  from and where it's going.  So this is a generic sort of  water budget.  And all of us know these things  from our checking accounts,  right.  Change in storage.  The storages are balance.  And that's as imports and  outputs fluctuate, the amount of  what's in store, in our bank  account, fluctuates as well.  So, these are very important  things.  They're very powerful things.  They're kind of annoying things,  but you've got to have them.  In science, they're really  important to us, because they  serve two purposes. 

 First of all, if we can write a  budget or balance for a  phenomenon that we're interested  in, that means that we  understand it pretty well.  Being able to account for all  the energy, or all of the water,  or all of the mass in a system  is a check on how well we  understand that whole system.  Likewise, if we write the  budget, and we can make it all  close up, if we can get all of  our sums to work out at the end  of the day, that means that we  have all the parts and our  measurements are really good.  Often, we can measure parts of  our budget well, but not other  parts.  So when we can close the budget,  that gives us confidence in our  measurements.  Well, the water budget for an  aquifer, then, without any  humans in action looks something  like this.  Here's our groundwater aquifer.  The change in storage here is  equal to the recharge minus the  discharge.  Recharge is water that, we'll  talk about this in greater  detail, but recharge is water  that, say, leaks out of the  bottom of the lake, for example.  It leaks downward and goes in  and enters into the aquifer,  drains through the soil and  reaches into the aquifer and  becomes groundwater. 

 Discharge is then the surface  manifestations that we've been  talking about already, springs,  lakes, and streams.  Now, if we're just thinking of a  little chunk of an aquifer, you  do have to account for the fact  that often, that water is moving  very slowly laterally.  So I've acknowledge that here,  that there's an inflow and an  outflow.  We're just concerned with the  portion of the aquifer.  We're not going to be worried  about those components for the  rest of this talk.  Well, once we add in wells, when  humans drill wells or dig wells  into an aquifer, it adds a new  discharge.  So here, I've depicted  irrigation wells, and municipal  and industrial wells as two  examples.  Certainly homeowner wells are  another form of well.  Those, coupled with the surface  water discharges that we talked  about become all of the  groundwater discharges that are  involved here.  Now, back in the day, our  withdrawals, when we built or  dug a well, our withdrawals were  pretty modest. 

 For example these women in  India, in order to get any water  out of that well, they have to  lower their bucket down, and  they have to pull that bucket  back up.  And then, probably carry that  water a mile or two home.  So, that pretty well slows down  limits to how much water they  can pull out of that, how  powerful that new discharge is,  how important that new discharge  is.  So that was the way it was many  years ago, and still is in parts  of the world.  But since World War II,  technology has come along.  We have very powerful pumps now  connected to electricity.  And we know how to fabricate  aluminum into large irrigation  machines like this one you see  photographed here.  And we can pump water out very  rapidly.  So the city of Madison has 25 or  30 wells that it's pumping on to  supply our needs in peak times  of summer.  Here's a shot from satellite of  Kansas. 

 And you see all the center pivot  irrigation systems that are  there.  Well, once you add a new  discharge to a system, as we  have here, your water budget  indicates that you really should  expect that the delta-S, the  change in storage, is going to  be negative.  Now, that assumes that we're in  sort of a steady state, and this  storage isn't changing very  much, which on average, would be  the case before humans dug the  well in.  So you put the well in, and  that's a new discharge.  You've got to figure that the  water budget says there's every  reason to believe that this is  going to cause a drop in the  amount of stored water, which is  manifested in the aquifers we're  talking here, as a change in  elevation of the water table.  Well, as a result then, if the  water table were to drop, the  amount of storage to drop a  little bit, it could be that  some of these other discharges  are going to be diminished or  drop off.  As the elevation of the water  drops, there's a chance that the  spring will go dry, or the  discharge into the river will be  reduced somewhat, or a lake goes  away.  Now, interestingly, the natural  discharges, such as springs and  lakes and rivers, discharge into  rivers, they're sort of  self-regulating.  When the water level drops down  a bit, those discharges decrease  somewhat.  A spring might dry up over a  period of several years of  drought. 

 And that kind of moderates the  loss, that stops the loss of  water.  Human wells, on the other hand,  aren't really subject to those  constraints.  We keep pumping on this  groundwater until, well, usually  until it becomes so deep that  it's too expensive for us to  pull it up for our purposes.  That's happened lots of places  around the United States and the  world, or the quality of the  water changes such that it's not  useful for our intended purposes  anymore.  Well, wells create a new  discharge.  And they start competing with  these other discharges, as we've  been talking.  Here's a schematic of the land  surface here.  This is the recharge area.  Water seeps down through the  land area, contributes to the  groundwater in the aquifer.  And it flows slowly here, and  discharges into this stream. 

 Now, in many cases, this  groundwater discharge, in our  part of the country, this  groundwater discharge is vital  to these streams.  It supports the stream flow.  So you introduce a well right  here, and you're intercepting,  you're going to intercept some  of that moving groundwater  that's headed for that stream.  So, it may or may not have an  impact.  Now, the changes may be small  compared to natural variation.  That would be good, if you're  lucky.  So picture the family budget,  and the first kid gets into  kindergarten and you have to  start giving an allowance to the  child.  That doesn't affect the family  budget very much.  But by the time that child goes  to UW-Madison, and you're paying  tuition, room and board, that  new draw on the budget is very  substantial, compared to the  other ones.  So maybe we can pump a little  bit of water out of here without  any other effect, depending on  how it compares with other  discharges. 

 But maybe not.  And the nature of recharge may  change as the groundwater level  drops down a little bit, as we  pull on our storage.  Well, what this means is, what  we have to do now then, to put  this all together, is to create  another water budget.  This one for the soil on top.  In order to understand the  effect of irrigation on the  groundwater budget, to fully  understand it, we'd have to  write a water budget now for  this soil.  So, here's a soil water budget.  It's the same general form.  Changes in storage are equal to  inputs minus outputs.  A couple of new terms here.  Here is precipitation and  irrigation, obvious inputs of  water to the soil. 

 Evaporation is a loss through  the leaves and from the soil.  And drainage.  Drainage from the soil.  What is drainage from the soil  is the all-critical recharge to  the groundwater budget.  So this is why we have to  understand this connection and  these two water budgets very  carefully.  So, evaporation, the word on  that.  That, is of course, occurs from  vegetative surfaces, and lakes,  and streams, wetlands, when  liquid water is converted into  vapor and carried off in the  atmosphere, swept off in the  atmosphere.  So your lawn, in July, on a nice  day, assuming that it's just  rained or you sprinkle it  properly, will evaporate from  it, will give up by evaporation,  a quarter to a third of inch of  water.  Think of it as reverse invisible  rain.  You can't see it, but every day,  if there's water in the soil,  it's evaporating away. 

 Reverse invisible rain.  So we have to put it all  together, this water budget, in  order to understand the effect  of irrigation, fully, on the  groundwater budget.  Now, as it turns out, we  actually need several different  groundwater budgets.  We need one for perennial  covers, for the perennial  vegetation.  So folks who have driven up  through there know that  perennial vegetation up there,  there are pine plantations.  There are prairie-like areas.  There are scrub.  There's abandoned farmland.  This vegetative cover has  certain characteristics that are  important.  One is the soil is always  covered. 

 Even right now, today, up there,  there's dormant plant material,  last year's grass.  The pine trees are still all  there.  They intercept a lot of  rainfall.  Rainfall falls and is held in  that vegetation and evaporates  back away before it ever gets a  chance to get to the soil.  So that's a special  characteristic of that perennial  vegetation.  They get going with their  evaporation right as soon as the  weather is good enough.  And right now, they're warming  up and thinking about springing  out some leaves, then the  evaporation will really pick up.  On the other hand though, the  evaporation of that perennial  vegetation is limited by the  soil water supply.  We don't irrigate it.  So it lives and dies on the  rain. 

 When the stored soil water gets  low enough, evaporation drops  off.  And that part of the budget  becomes smaller.  In contrast, we have our annual  crops that have different  characteristics.  They have long periods of bare  soil.  You go up there, most of the  agricultural fields don't have  much on them.  They might have a little bit of  a cover crop popping up, tiny  leaves, but lots of bare soil  also.  Then all during the summer, it's  covered with green vegetation,  and water it enough so that it's  always evaporating just as fast  as it can, at what we call the  potential evaporation rate.  So in contrast to perennial  vegetation that's living and  dying on whether it rains, these  crop lands are cooking away at  full speed.  So, we need to write several  different water budgets for this  situation.  Now, the really big question  that we have to treat here is,  how do these different water  budgets differ in net recharge. 

 We can imagine that the  perennial has the advantage that  it slows down its evaporation  and slows its evaporation when  the soil is really dry.  In contrast, the annual crop, in  terms of net recharge, has this  big term of irrigation being  pulled out.  So we have to subtract that from  whatever recharge can make it  through, to think about the net  recharge.  So I want to make mention here  of some of the simulation  results that we've been doing.  This is what we call a toy  model.  I've been working on this about  a year.  It's a very simple little model  to think about how does net  recharge differ between the  different land uses.  So, this is a very complicated  graph, but we'll walk through it  quite slowly here.  Across the bottom is annual  precipitation.  So it runs from 500mm to 1000mm. 

 over that period, from about  1950 to 2007.  This is about 31 inches right in  here.  The average is about 32 to 36  inches, right about here.  So, average rainfall is right in  this vicinity.  Now, on this axis is the annual  recharge from the different land  uses.  So, we have two different land  uses here that we've simulated.  Perennial is kind of a generic  perennial vegetation, meter deep  root system that, again, it's  E-T goes by how much water is in  the soil, and recent rainfall.  And then, irrigated vegetation.  Let's look first at the  perennial results.  Here are these open circles. 

 And what we see is this family  of points, that are all kind of  generally gathered around a line  that's running up this way,  right?  So now, for this perennial  vegetation, the annual recharge  never goes below zero.  If you get a really dry year, no  water gets through, but it never  goes negative, because there's  no irrigation or pumping from  there.  So this gets down here to a very  low value, but never lower than  zero.  In contrast, then, this  irrigated crop.  And again, this is kind of a  generic irrigated crop that I've  modeled here.  It's net recharge runs about the  same along a line like that.  It goes negative a lot of years.  In a very dry year, where there  isn't much natural rainfall at  all, but lots of irrigation  pumping then.  In fact, we have a net,  or negative recharge from  that kind of a vegetation.  So, that can get very dry. 

 Now, as I mentioned before, what  we're really interested in is  what's the difference between  these two kinds of vegetation  and their annual recharge.  So, that, we've calculated,  taken the difference.  We've subtracted the recharge  from the perennial vegetation.  So before we developed our  irrigation in this region, that  was perennial vegetation, and  every time we put in a new acre  of irrigated lands, we tore out  the perennial vegetation.  We put in irrigated lands and a  pumping system.  So, what we're interested in is  the difference in any one year  between what a perennial land  cover would give, in terms of  recharge, compared to what, in  that same year, the net recharge  from irrigated land.  So, for every year then, is a  pair of dots here.  So in this year, the annual  recharge from perennial  vegetation was 320-330.  And that from the irrigated  lands was a bit less, at 220.  So, we subtracted their  difference. 

 And instead of putting all the  points on there, I just put a  single line on here.  And what we find is at the  average rainfall, so for the  average year over the whole  period, the difference in  recharge is about two inches,  annual recharge.  We're estimating with this model  a difference of just about two  inches.  Now, we have other models that  graduate students are working  on.  They're much more ornate.  It doesn't make them more  correct.  But they're considerably more  ornate than this little toy  model I've done.  And they're indicating to us  that this difference could be  four inches.  So this is probably a  conservative difference.  And we have to sort out why my  little toy model only says two,  and this more ornate one says  four. 

 But this is probably  a conservative estimate.  So, that's two inches difference  in annual recharge.  What does that mean in terms of  the groundwater?  You recall back here, we have to  put together this whole picture,  where the net recharge then is  an important part of the  groundwater component, and  influences the changing water  stored.  Well, my colleague at Stevens  Point, George Kraft, he's a  hydro-geologist up there at the  UW-Stevens Point Center for  Groundwater.  He's been studying the  groundwater in that area, the  saturated part in the aquifers.  He's been studying that for  decades.  He has complicated models of it.  What he has calculated,  estimates, is he can estimate  the drop in the water table for  every inch of foregone recharge.  So, when we switch from the  perennial vegetation to  irrigated lands, which is of  course an important driver of  the economy up there, there's a  cost in foregone recharge to the  groundwater.  And the question is, how big is  that, and how important is that  for the water table. 

 So, his modeling is of the  groundwater part of it.  My model is about the top layer,  the soil.  He's all about the groundwater.  And he says that if he loses an  inch of recharge, you forego an  inch of recharge, for whatever  reason, he can estimate how many  feet the water table would drop.  Now, the water table drops, you  remember seeing the trace of  groundwater levels from the  observation well.  It's manifested in that.  It's manifested in lakes going  dry, and in rivers going dry.  So right here, on his most  recent analysis, there's this  bulls eye right there, where he  estimates than an inch of lost  or foregone recharge results in,  for whatever reason, results in  potential change in the  groundwater level of two feet.  So, if I'm proposing that  there's about two inches of lost  recharge, multiply that times  this, gives you four or five  feet of drop in groundwater that  could be as a result of the  pumping in this area.  Now, his estimate requires an  assumption on how much recharge  is foregone, and what fraction  of the area is covered by  irrigation. 

 And you know that by  observations and from the  census.  So, here's our friend out  standing on his pier.  And we find that it does seem  that as a result of the  conversion of the amount of land  that's been converted to  irrigated lands, the result in  net recharge could explain  what's happened to the  groundwater in the region.  So, in summary, the area here  under irrigation has been  increasing for decades.  We know this.  There is less net recharge from  irrigated lands compared to  perennial vegetation.  My little toy model says maybe  on average two inches.  We have other models that say it  could be twice that.  It could be four inches in an  average year.  But it's a function of how much  it rains in a year. 

 And this lost recharge, then,  when coupled with a groundwater  model, comes close to matching  the observations that we see  related to the lower lake  levels.  Now, here's a fellow that all of  us know, John Muir, a famous  environmentalist.  Migrated from Scotland and lived  in Baraboo.  He attended UW-Madison for a  semester or a while.  It didn't last long, didn't  engage him quite enough.  But he has a quote here that  environmentalists are very fond  of.  "When one tugs at a single thing  in nature, he finds it attached  to the rest of the world."  Well, I find that a little  over the top.  I don't think everything is  quite that intimately connected.  Whether I had Mini Wheats  or Corn Chex for breakfast this  morning, no one will ever know,  and it just doesn't matter  in any practical sense.  So that's a bit of an  overstatement. 

 But there is another expression  that I like.  And I've seen it attributed to  various speakers, various  environmental thinkers,  so I don't really know  where it originated.  But this idea that you  can't do just one thing.  And I think that's probably  quite applicable.  That should be the starting  assumption about our effects  of human appropriation  on groundwater in the central  sands.  So again, here you see we add  a new well, we have some impact.  So the question is,  is this impact--  Is this impact large enough  for anyone to measure?  Is it large enough to come out  of the noise of natural  variation?  Is it an impact on something  that anyone cares about?  Those are important questions  that have to be answered.  So, we've talked about the  groundwater resource.  We've talked about the idea of  water budgets, and some  indication that there's probably  pretty good reason to believe  that if we have enough  irrigation up in that region,  coupled with municipal pumping,  which is important close to the  municipal areas, to have had a  significant impact on the  groundwater level.  Thank you. 

 (applause)