A press release I never quite finished reading

Snow_riverNature Climate Change asks this:

How does snow affect the amount of water in rivers?
New research has shown for the first time that the amount of water flowing through rivers in snow-affected regions depends significantly on how much of the precipitation falls as snowfall. This means in a warming climate, if less of the precipitation falls as snow, rivers will discharge less water than they currently do.

From the University of Bristol  and the department of obvious science.

How does snow affect the amount of water in rivers?

New research has shown for the first time that the amount of water flowing through rivers in snow-affected regions depends significantly on how much of the precipitation falls as snowfall. This means in a warming climate, if less of the precipitation falls as snow, rivers will discharge less water than they currently do.

The study by PhD student Wouter Berghuijs and Dr Ross Woods, Senior Lecturer in Water and Environmental Engineering in the Department of Civil Engineering at the University of Bristol together with a colleague from Delft University of Technology is published online in Nature Climate Change.

The researchers, using historical data from several hundred river basins located across the United States, investigated the effect of snow on the amount of water that rivers discharge.

How river flow is generated in snowy areas is poorly understood due to the difficulty in getting appropriate measurements. Previous studies have mostly focused on the role of snowfall for the within-year distribution of streamflow – how much water is there in the river during a particular period of the year – and assumed that there was no important effect of snow on the average streamflow. This study is the first to focus on the role of snow for how much water is on average available in rivers.

With data from 420 catchments located throughout the United States the researchers show that snowiness is an important factor for the average river discharge.

Global warming is very likely to reduce the amount of snow significantly in snow-affected catchments, even if temperatures rise only two degrees Celsius. The new research suggests that the amount of water in rivers will be reduced as a result of the decrease in snow.

The authors of the study said: “With more than one-sixth of the Earth’s population depending on meltwater for their water supply, and ecosystems that can be sensitive to streamflow alterations, the socio-economic consequences of a reduction in streamflow can be substantial.

“Our finding is particularly relevant to regions where societally important functions, such ecosystem stability, hydropower, irrigation, and industrial or domestic water supply are derived from snowmelt.”

Given this importance of streamflow for society, the researchers propose that further studies are required to respond to the consequences of a temperature-induced precipitation shift from snow to rain.

###

Paper: A precipitation shift from snow towards rain leads to a decrease in streamflow, W. R. Berghuijs, R. A.Woods and M. Hrachowitz, Nature Climate Change, Vol 4, June 2014.

PR Source: Eurekalert http://www.eurekalert.org/pub_releases/2014-05/uob-hds051614.php

About these ads

77 thoughts on “A press release I never quite finished reading

  1. In New England, warming climate will lead to trees getting a longer growing season and they’ll have more days to suck up most of the rain fall. So if the annual precip amount stays the same, there will be less water in the rivers and more transpiration from the leaves.

  2. In a, fictional, warmer world, rain would replace snow.
    Overal precipitation is supposed to increase…
    I suggest the best use for these “studies presupposing a warming world” have one use only.
    A means of identifying useless feeders upon the public purse.

  3. “Global warming is very likely to reduce the amount of snow significantly in snow-affected catchments, even if temperatures rise only two degrees Celsius.”

    very funny. So, even minimal global smarming / thermageddon /climate change/ climate disruption might/could/should/possibly would plus or minus 2% to 500% change snowfall if only 2 degrees C rise which is right on schedule predicted in about 2.5 centuries or so at .8 degrees per century plus or minus 3 degrees C.

    I am gonna hold my breath and sulk, yes indeed !!

  4. I would think that water from rain reaches rivers quickly, while snow persists through the winter, then melts over spring & summer providing graduated discharge to rivers. Presumably water is more important to agriculture in the spring and summer, so there is value in having snow delay the discharge. Of course, if it doesn’t snow, then perhaps there might be year-round agriculture as in the tropics?

  5. Is it possible that some educated persons might send the Alarmists no matter if the later has or hasn’t degree or scholartitle a hint of what every 4th grader around the world should have learnt – the Water cycle? Sadly enough the alarmists seems to have missed that essential part.

  6. The first thought that popped into my mind was an old “Merry Melodies/Bugs Bunny cartoon. The one with the two British accented owls and the big dumb American accented vulture ….

    “Beakey, what makes you so incredibly stupid?!?

  7. Every news release start with “New research shows for the very first time …”

    It doesn’t matter what topic it is. Its the new introductory sentence from university PR departments. Obviously, it is almost never “the first time”, but they like the “spin”.

    If it starts with “spin”, then the rest of it is most likely just more spin.

  8. B.S. Snowfall moisture is based upon the temperature it is formed. Warmer the temperature the more moisture is in it! As a person who lives in Snowy and Cold Climate of Minnesota, this is crap research. For Example a quarter inch of rain can produce either 1 inch of snow or 4 inches of snow depending upon the temperature, While a quarter of rain at any temp is still the same. So instead of it falling as snow it will fall as rain. LOL, too much stupidity from people who dont have a clue about cold and snow. FYI last winter i recorded a low of -23.9 F. As a side note i think we need to stop recording snowfall in inches of depth and only measure content of moisture, because 96 inches of snow one season isn’t the same as 96 inches of snow in another since moisture content varies!

  9. Let’s see, precipitation (rain & snow) changes with regard to the ratio between rain and snow, but overall in a warmer world there is more precipitation. And we are being told that more rain and less snow equals less flow in the rivers.
    How stupid do they think we all are?

  10. They already knew this:
    With more than one-sixth of the Earth’s population depending on meltwater for their water supply

    But they didn’t know this:
    New research has shown for the first time that the amount of water flowing through rivers in snow-affected regions depends significantly on how much of the precipitation falls as snowfall.

    …and they got paid what for this?

  11. Joe Chang:

    I’m guessing you don’t live in snow country. When the snow goes, it goes in a week to four weeks. Longer if mother nature is kind. Shorter if there is heavy rain.

  12. It’s not obvious science. It asks the relevant question, how does the amount of river runoff vary depending on whether a given amount of precipitation falls as rain or snow? Is that something you all knew?

  13. Meh. Snow allows the trees to have a more continuous supply of water. No snow, trees die. Less trees, more albedo and more water available to people. It’s win-win-win. Or it’s such a narrow view of the entire coupled process as to be virtually useless information.

  14. The statement “How river flow is generated in snowy areas is poorly understood due to the difficulty in getting appropriate measurements. ” tells me these people don’t know what they are talking about. In Ontario, the electrical utility measures snow pack regularly and has a clear view of how many inches of water it contains. This is used by many parties to estimate how much runoff there will be (this has been going on for decades). Also, there are two periods of increased water flow. The spring freshet, associated with snow melt and the fall freshet associated with precipitation from the contrast of the impending winter and the departing summer (for want of a shorter term, Joe Bastardi could give a long and detailed description I’m sure). How river flow is generated in snowy areas is VERY well understood. How did this pass peer review?

  15. They don’t seem to have gotten the latest memo that Global Warming is causing harsher winters and more snow. This is self-evident because, since the debate is over and we are experiencing Global Warming/ClimateChange/Climate Disruption/Climate Pollution from CO2 and we seem to be having harsher winters and more snow … therefore GW/CC/CD/CP cause more snow and harsher winters.

    Never mind that 5 years ago GW/CC/CD/CP caused far less snow, that was then, this is now.

  16. Nick Stokes: Nothing in science is obvious. Else Aristotle would have known that F=ma. This “study” is rehashing settled science, or to use the appropriate term for “settled science”: engineering. Civil engineers have been doing this type of work for years. It is somewhat important in things like dam design. The authors of this study have reinvented a wheel. And a hand chiseled stone wheel at that.

  17. John Eggert says: “How did this pass peer review?” ROFL, that was a rhetorical question, yes?

    It passed peer review because it said the magic words ‘Global Warming is bad’, at least more or less.

  18. “It’s not obvious science. It asks the relevant question, how does the amount of river runoff vary depending on whether a given amount of precipitation falls as rain or snow? Is that something you all knew?”

    It isn’t something ‘I’ knew, and, even after reading the paper I ‘still’ don’t know. I’m not sure how that lack of knowledge is relevant to the issue. It is something Civil Engineers building dams to control flooding better know else they run the risk of either over building or under building the dams.

  19. john robertson, the best use for these type of studies is to be linked in roll for use next to the toilet.

  20. You don’t need to live in a snowy country to know that.

    Even here in Brazil, a virtually snowless country, small kids in school learn about the water volume in the Amazon River basin depending on the melting of the winter snow on the Andes…

    Indeed, “How did this pass peer review?”

  21. Nature Climate Change asks this:

    How does snow affect the amount of water in rivers?

    Practise, practise, practise?

  22. How much of this BS can these alarmists continue to serve up?
    Before the people of the world tell them, “your funding is going to be put to better use.”
    I mean I read on a daily basis a report or some times multiple reports that have possible cost millions in funding to produce.
    That mean absolutely nothing.
    We have people sleeping under bridges in my country, “the lucky country” yet we to give funding to alarmists like this example uselessness.
    It has to stop.

  23. The water content in snow pack and the conditions of the melt season are bigger measures of water flow in rivers during the summer/fall season. Snow pack and melt rate have been studied and results used for decades to manage water resources for agriculture purposes in closed ecosystems like Wallowa County. This article sounds like the authors are at the kindergarten stage.

  24. This just in…. it’s dark at night because the sun is not shining on that part of the planet.

  25. This makes at least a little sense; precipitation that falls as rain runs downstream IMMEDIATELY, while snow remains on the ground and flows downstream at the rate of the snow melting.

    Further, in places like the Sierra Nevada, rain not only runs downstream immediately, it also causes accelerated snowmelt.

    So if the goal is a constant flow in the river rather than flood and drought, we either need precip as snow, or we need dams and reservoirs to control the downstream flow. Good thing we have them!

  26. John Eggert says:
    This “study” is rehashing settled science, or to use the appropriate term for “settled science”: engineering. Civil engineers have been doing this type of work for years.

    The study by PhD student Wouter Berghuijs and Dr Ross Woods, Senior Lecturer in Water and Environmental Engineering in the Department of Civil Engineering at the University of Bristol…

    This is not my area field but it seems to me someone with a PhD in Engineering would know what has been done in the field. So either the first statement is incorrect or Dr. Woods does not know the field.

  27. When it’s cold enough for snow instead of rain, the ground is frozen and water does not soak into the ground. It runs off into the streams as it melts.

    When it is warm enough for rain, the ground is thawed and water soaks in instead of running off.

  28. Darn and here I thought that global warming meant more snowy winters like the one parts of the US just had, this really “not obvious science.”

  29. Re: Bill Illis says:
    May 18, 2014 at 5:27 pm

    “Every news release start with “New research shows for the very first time …”

    And every one ends with “Further study (money) will be required.”

    And what every one of them knows but does NOT say is that “We knew if we didn’t link this to support of AGW, we probably wouldn’t get published, wouldn’t receive recognition from the news media and wouldn’t receive additional funding for ‘further study'”.

  30. MaxLD: I would have thought someone with a PhD would know too. I’ve measured, estimated and projected water balances (which includes stream flows in and out) in a catchment area as part of my routine tasks. The projections, related to 100 year events, looked at what would happen if various extreme events occurred. The impacts of lower snow pack, higher snow pack, early snow pack, heavy autumn rain, early deep snow, etc., etc., are all easily determined. If the extreme event is a very late fall and very early spring, you’ve covered “climate change”. Technicians do this. Engineers merely check their work.

  31. A significant fraction of precipitation as snow is lost through sublimation. Rain will either run off or flow as groundwater. Certainly some will be lost through evaporation, but not during the precipitation event. Did the authors confuse total discharge and peak discharge? Peak snow melt will occur in spring, Multiple rainfall in a season would tend to decrease snow pack and reduce peak discharge unless a powerful late winter warm storm melts a substantial snow pack. The point is, if it rains, the water will stay on (lakes, streams) or in the ground. If it snows, a lot of the moisture will be lost to the air (typically from tree branches). Thus, it is likely the paper is quite wrong.

  32. And here just a last winter Judith Curry was predicting MORE snow across Europe and Asia and Canada due to MORE evaporation from the ever-more-exposed Arctic Ocean as the Arctic sea ice extents become lower!

  33. Their next paper will be on the effect of July snows on the flow of the Mississippi.

  34. John Eggert: I have lived my days in Alberta and BC Canada where forecasting river flow is a pretty important task, especially in the spring with snow melt and rain events. I too would have thought that snow pack and rainfall amounts would be a routine input into the forecast models and decision making. And testing different scenarios would be part of the process. I have not read the paper in question so maybe there is something new in it that I am missing.

  35. ‘Brian M. Babey says:May 18, 2014 at 5:35 pm
    B.S. Snowfall moisture is based upon the temperature it is formed. Warmer the temperature the more moisture is in it! As a person who lives in Snowy and Cold Climate of Minnesota, this is crap research. For Example a quarter inch of rain can produce either 1 inch of snow or 4 inches of snow depending upon the……’
    Here’s the sad part The study was paid for with tax payer’s money.

  36. Does this explain the reason why during the Little Ice Age, Europe encountered extreme flooding that drowned people in the hundreds of thousands?

  37. What morons, the Red River of the north flood in the spring due to a heavy snow pack it may be at best a month long event, All that water heads to Hudson bay at an alarming rate, none is saved. It gone not stored so how does that help; Fargo and Grand forks water supply problems., I have watch Red rives cease flowing in July August. time frame three time in my adult life. The spring run of is just that, it is does not rain in May June and July it will cease flowing, there are very no dams on the Red to hold the spring water back, the only dam of not is on the Sheyenne, the Bald Hill dam, the Sheyenne dumps into the Red north of Fargo, In order to assure Fargo is able to get that water if need there is a diversion. The plan in the fifties was to use Missouri river water out of Lake Sakakawea to assure the Red River Valley cities a reliable water supply but the Greenies made sure that did not happen.

  38. ‘ This means in a warming climate, if less of the precipitation falls as snow, rivers will discharge less water than they currently do.’

    Sea levels will fall – we are all doomed.

  39. Nick Stokes says:
    May 18, 2014 at 5:51 pm: “…It’s not obvious science. It asks the relevant question, how does the amount of river runoff vary depending on whether a given amount of precipitation falls as rain or snow? Is that something you all knew?…” Nick, anyone who lives in snow country knows this inside and out. It’s as obvious as a dogs’ balls. We go through it every year. If it gets hot early, then FLOOD. If it’s cold and snowy well into May, then we just have the normal runoff. (For your info, there is STILL snow to be found in our forests, here in the UP, on the north side of hills and road embankments, and so on). And, there is still standing water in many places, that will take a good while to percolate through the hardpan, and thence into the streams and rivers. But a two inch downpour causes the rivers and streams to rise and flow that fast.

    The question I want to ask, is, how truly stupid, arrogant and unknowing about the world are you? What are you, who has some snide remark to offer all the “deniers” here? We would really like to see your CV, and all the exalted degrees from exalted Universities, so we can give you proper respect.

  40. “It is something Civil Engineers building dams to control flooding better know else they run the risk of either over building or under building the dams.”
    etc
    Lots of people talking about transient snowmelt pulses etc. That’s not what this paper is about. The release says:
    “Previous studies have mostly focused on the role of snowfall for the within-year distribution of streamflow – how much water is there in the river during a particular period of the year – and assumed that there was no important effect of snow on the average streamflow.”

    “This study is the first to focus on the role of snow for how much water is on average available in rivers.”

    I would have guessed snow, because the air is generally colder when it is on the ground. But it’s on the ground a lot longer.

    It’s worth finding out.

  41. These people are simpletons. Here in the Rocky Mnts. the ground water and springs have to be fully charged, usually by fall rain for the spring runoff to be at it maximum.

  42. Agreed, not worth reading.
    In Colorado they watch accumulation of snow and water equivalency, time of accumulation maximum, and continual water flow rates for the Colorado River at least, the data already exists and they aren’t looking at it. Typical.

  43. In the 1980’s I lived next door to a helicopter pilot who assisted the Seattle Water Dept. with snow surveys in the winter/spring. (On the 34th anniversary of the eruption of Mt. St. Helens, a h/t to Lon, a former Chinook driver. He flew many hours in support of various agencies in the days afterwards.) AIR, he said it wasn’t just the depth of the snow, but how much water was in it.
    I can only get the abstract, but surely the authors know that the USDA implemented the Snow Survey and Water Supply Forecasting (SSWSF) in 1935. The current Snow Telemetry (SNOTEL) system provides ongoing data to the Natural Resources Conservation Service. Not sure they can speak for other countries, but I am sure the US is well served by the employees of the National Water and Climate Center.
    If this is an going field of study, I recommend the authors sign up for the quarterly SnowNews for info on the US.

  44. Jason H says: “Global warming causes less snow, except when it causes more snow…”

    No, no, Jason. Global warming causes less snow AND more snow AT THE SAME TIME.

  45. So if snow affects the amount of water in rivers, what’s in store for us folks in Texas?
    Mike in Houston

  46. Nick Stokes states, “It’s not obvious science. It asks the relevant question, how does the amount of river runoff vary depending on whether a given amount of precipitation falls as rain or snow? Is that something you all knew?”

    Sir – every rancher/farmer in the area I was raised who possessed only a sixth-grade education have known for generations exactly what the fall/winter/spring snowfall/rainfall amounts and the differences thereof meant to irrigation for the spring/summer/fall planting/growing/harvesting season.

    You should have expressed surprise, instead, that city slickers (to whom the science was not obvious) should have taken so long to discover those facts.

  47. Nick Stokes: Your point is well taken. The study focuses on the average streamflow, not the transient flow. They find that this depends more on average snowfall than rainfall. As you say, it is worth finding out. If anyone commenting has actually read the paper, maybe they could provide more insight.

  48. “Given this importance of streamflow for society, the researchers propose that further studies are required to respond to the consequences of a temperature-induced precipitation shift from snow to rain.”

    The bottom line. Give us more money please.

  49. If one expects less flow it follows that the capture of more water is necessary. The logical solution is more dams and increased capture of the water available for storage. Do you think the green pay masters would agree?

  50. This paper marries perfectly with my theory that snow is made entirely of water.
    Before any carbonazis who lurk here and wish to pick on me and totally refute it, it’s only a personal theory derived from models.

  51. So there will be less runoff according to this warmist but more floods according to others. And the media will report AGW caused water shortages and AGW caused floods. It’s cool how that works.

  52. My wife and I take twice daily readings every day of the year (as do many volunteers every day across North America) re, rain fall, snow depth, snow on ground and dew . The only thing this article reminds me of it is a….

    SNOWJOB!

  53. Is this new? Really? Cause I thought papers weren’t supposed to be published if they didn’t cover new ground? Or is that only when they don’t support an alarming idea?

  54. I’ve been at the base of m/any “glaciers” in the Canadian Rocky Mountains. I’ve read good travel stories of others following drainages that start as glaciers in the Andes. The situation is the same: the direct amount of melt is small coming from the ice masses, but the rives downstream are full and raging. Why? Because rainfall and snowmelt (going into the water table) are the dominant sources of water in all rivers.

    Look at the waterflow in all signficant rivers that are sourced in glaciers (except, of course, Greenland or Antarctica) and you’ll find the same. It is general precipitation that counts. The world experiences roughly 1000 mm of rainfall/precipitation per m2 per year. The direct portion that is glacial fed is small, obviously, when the oceans are rising at about 2 mm/yr.

  55. Nick Stokes says:
    May 18, 2014 at 5:51 pm

    It’s not obvious science. It asks the relevant question, how does the amount of river runoff vary depending on whether a given amount of precipitation falls as rain or snow? Is that something you all knew?

    Pretty much, yes. You didn’t?

  56. There are these things called hydrologists that study and understand river flows. I am one of them. Snowmelt is well understood and there aew several well established snow melt models so what exactly new or novel are these fools doing? Plus they are totally wrong! When snow accumulates low flow is reduced and theb in melt season elevated. If less snow there will be reduced annual varriation in low flow but the mean flow does not change. It only changes if net precipitation changes and that varies massively from year to year.

  57. “Well, then I guess it’s a good thing that the trend for fall and winter snowfall in the Northern Hemisphere winter is up!”

    Winter snowfall plots better as a shift in mean snow extent starting 2007..

    NHWinterSnowChart

    Exhibits as 7 points above the long term mean, with an average extent about 1,5 km2 greater.

  58. Another “Given global warming, . . . .” study.

    ========

    Bill Illis says:
    May 18, 2014 at 5:27 pm

    Every news release start with “New research shows for the very first time …”

    ========

    Not only that, they have to trash previous studies by saying how deeply flawed they were.

  59. I am not a hydrologist, but I have watched my local river (the Missouri) for over 24 years now. I can say the river flow is probably way more complicated, as well as better known by practicing hydrologists, than these authors suggest.

  60. tumpy said it best, and, as usual, Stokes is spouting nonsense. It requires little, if any, intelligence to realize that precipitation is precipitation (i.e. water is water) and whether it appears out of the sky as snow or rain has nothing to do with the total amount of water we receive, and which will eventually end up in the rivers. So, in effect, these morons are actually claiming is that a
    warmer Earth is a drier Earth, which is not true if you believe either the other global warming alarmists or the skeptics. Or you possess a brain. This study is so dumb I wonder whether even alarmists, other than deadenders like Stokes, will buy into this nonsense.

  61. Not going to pretend I read the paper. I am going to have to ask how did they come up with their comparative answer, though, by parallel worlds where they could see what happened in a given river when the climate provided the precipitation in the form of snow in one and rain in the other, or did they use (I hate to use this phrase) computer simulation to create their data? I can’t see how you could actually claim to know as a truth that precipitation falling as snow causes greater average stream flow any other way.

    Since parallel worlds are probably not available to the researchers, then the computer simulation has to be the route they used, and when you are coding in your belief set, oddly enough, the program outputs proof of your beliefs. Why is it that the climate change people can’t understand that a computer simulation can only output according to the sum total of the variables they choose, and if they don’t choose ALL of the variables, they can NOT get an accurate output from the simulation? But of course, they already know that, just as do the politicians that use these simulations to scare people, do as well. It’s only the under educated population that doesn’t.

  62. Nick Stokes says:

    It’s not obvious science.

    Rather, it is obviously not science.

    It asks the relevant question, how does the amount of river runoff vary depending on whether a given amount of precipitation falls as rain or snow?

    That is not the relevant question.

    Given that “global warming” theory also asserts that overall precipitation over land will increase in response to the same mechanism that is situationally asserted to cause both more snowfall and less snowfall, the relevant question is – What is the net effect?

    That is not the question asked by this “science”, but it is the question being “answered” by this “science”. Completely unscientific bullshit.

    If (as “global warming” theory asserts) more precipitation will fall on land

    and if (as “global warming” theory now also asserts) less precipitation will be discharged by rivers

    then where the F@#$ is all that water going?

    corollary conclusion If more precipitation falls on land, but less is discharged from rivers into the sea … then “global warming” will cause sea level to decline!

    Woo hoo! Turns out that the cure for “global warming” is … “global warming”.

    Is that something you all knew?

    What we all know is that there is no coherent theory of climate. All there is are a bunch of disconnected and frequently contradictory assertions about how little pieces of a massively multivariate and recursive system might work.

    Well, there is that plus a bunch of political actors pretending to be scientists spinning each of those disconnected factoids into a wholly inconsistent narrative of original sin and retribution with a conveniently left wing political “solution”. That is the current state of “climate science”, and that is why the models don’t work. And why the more the models fail the more that confidence in them is more loudly asserted.

    Utter bullshit.

  63. When precipitation falls as rain, it could evaporate and fall again before it gets to a river. So there might be some double counting. It is important to look at the overall effect.

  64. Several points not mentioned in this study at this point : if snow precip gets to the river but rain precip not as much, where did the missing rain precip go? Also,why the implied claim that precip going into the river is preferable to precip going elsewhere? What do they consider a “significant missing amount” to be, and why? Until there are satisfactory answers to these questions, I will :
    1) not believe their data and 2) until that data is enumerated, not believe it makes any meaningful difference whether the precip went where they think it should have gone, without some logical arguments that make sense (not holding my breath). I also don’t believe they have any clear and irrefutable correlations beween avg temps and snowfall amounts. And I KNOW they have no knowledge of future temps. They also have failed to show that less river flow and more precip NOT going into the rivers is not beneficial. They have chosen to adopt but one view of the effects, which means they haven’t done their job as investigators. We all know that precip runoffs do no good for the flora and crops, etc.

  65. their next paper will be on the unexpected rise in temperature with the sunrise and the unexpected fall in temperature with the sunset …

  66. Eli Rabett says (May 19, 2014 at 8:03 am): “This almost surely has to do more with increased evaporation in a warmer world than precipitation.”‘

    According to the abstract, they applied “the Budyko water balance framework to catchments located throughout the contiguous United States.”

    http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2246.html

    A quick Google search and… “The Budyko hypothesis describes the annual water balance as a function of available water and energy. Mean annual actual evapotranspiration approaches mean annual precipitation as the climate becomes drier, assuming the long-term change in basin water storage is negligible.”

    http://adsabs.harvard.edu/abs/2010AGUFM.H23D1231W

    Intuitively, this makes sense. Snow is cold, and when it melts it’s still cold, so less evaporates while running off than warmer rain would. River catchments where snow falls are presumably colder than warmer areas where it rains, so there is slower–and later–plant growth and so less water is lost via transpiration. Result: more runoff for the river.

    So if I’m interpreting this paper correctly, the authors are making the rather banal prediction that–all else being equal–a river with a cooler catchment area will lose less water to “evapotranspiration” than the same river with a warmer catchment area. Seems reasonable as far as it goes, but of course as we all know, “all else” is never equal.

  67. ‘jorgekafkazar says: May 18, 2014 at 8:49 pm
    Jason H says: “Global warming causes less snow, except when it causes more snow…”
    No, no, Jason. Global warming causes less snow AND more snow AT THE SAME TIME.’

    NO..NO..NO
    You both got it wrong. Global warming causes more snow AND less snow AT THE SAME TIME.
    or “Global warming causes more snow, except when it causes less snow…”
    And I got a computer to prove it.

  68. @Col Mosby What do they consider a “significant missing amount” to be..

    As I read it, for every increase of 1% in the snow fraction (annual percent of precipitation falling as snow) they observed a 0.29% increase in the percent of the precipitation which ended up as streamflow, when considering the annual mean across 97 catchments with significant snowfall

  69. @Col Mosby where did the missing rain precip go?

    They don’t say but suggest a variety of possible explanations:

    “The observation that a lower (snow fraction) is associated with lower streamflow on the annual and mean-annual timescales is restricted here to empirical evidence, and does not reveal the physical processes behind these observations.”

    “The processes underlying the sensitivity of streamflow changes due to snowfall for individual catchments may be related to differences in water storage dynamics, flow paths and evaporation due to changes in the infiltration capacity of soils, the duration of infiltration periods, the timing of infiltration periods, the evaporation from snow-covered and snow-free soils, the growing season length, the soil moisture regime, the potential evaporation, amongst other factors.”

Comments are closed.