Another very stimulating article. Measuring rainfall P, is almost a lost cause. In our farming community, we all keep rainfall records and we all marvel at the fact that, in some years, one farmer might record 1200mm of rain while another (15kms away) only records 400. But our sample rate is approximately 1 in a billion (a single rain-gauge for a 1000ha farm). Any statistic based on such a low sampling rate is meaningless, ESPECIALLY for a parameter with as much variability as rainfall.
The disappointing thing from that analysis of the Chinese efforts to re-green their environment (and so their rainfall) was that the increase was only 1.24mm/year - after a greater than 16% increase in leaf cover. That seems very disappointing. However, the Climate IS non-linear, so perhaps a 25% increase in leaf cover will suddenly produce a 50mm/year increase in rainfall.
What is encouraging is that both China and India, two of the most densely populated countries on Earth have both managed to increase their leaf cover by > 16%. If they can do it, then we all can.
Don't forget that, from an Agricultural perspective, it is not just the total amount of rain, but the length of the growing season, that is very important. Trees can, if they can still access sufficient moisture through their roots (from a water table that has not been sucked too low) initiate rainfall earlier in the season, and sustain it longer into the dry season, than any other vegetation cover. (A phenomenon that you have mentioned has been demonstrated in South America.)
I am sorry that I won't be able to attend your discussion tomorrow. I hope a recording will be available on You Tube afterwards.
Hello, Bruce, "the increase was only 1.24mm/year" reflects some confusion in reporting the units. Precipitation is measured in mm/year, but sometimes per year is omitted as if it is self-evident. Then trends in precipitation, which should be in mm/year/year (i.e., how a flow measured in mm per year changes per year) becomes simply mm/year. In reality, after reading the paper, it becomes clear that here they talk about a trend, which in 20 years of re-greening would result in an additional precipitation of 20+ mm/year.
You are right, a trend of 1.24mm/year/year IS worth getting excited about, but then it begs the question as to when will that trend level off? Rainfall in China is unlikely to increase indefinitely . . . . . but no doubt you will discuss that at some time in the future.
HI Anastasia, I made a note earlier about the devastating impact of the 2015 El Nino and the dramatic drop in global above ground water storage which has not recovered. the point being that the massive die off of tropical trees and the time it takes to regrow have very long lasting effects which is what I think the graphs are really showing which also have altered cloud mass, Wm2 and associated albedo. the graphs are included in this note
One then could reason is that the water availability is just locked in the above ground vegetation that is obviously increasing.
I also did a quick analysis of the impact of spreader levees on flat semi arid areas of the world with this in mind and the results of being able to change the available water coefficient into vegetation and ground water recharge were remarkable. Instead of up to 90% loss from hydrophobic soils, spreader levees can change this to under 50% and rehydrate areas down stream that do not even receive any rainfall. This is currently being trialed in Australia and I made a post from a quick AI analysis online for anyone to look at.
Thank you, Anastassia, for explaining so clearly how the measurements necessary to the task of determining fluxes of water into and out of an area are undertaken, and how complicated and uncertain they inherently are.
This places all of our endeavors towards understanding in an important real-world-science context. It is not just word-problems.
Thanks for this, Anastassia. It helps demystify some of this basic hydrology.
A couple things puzzle me.
1. Millan Millan believed "water begets water." Part of how he saw this happening was by land milking the atmosphere, which it did by adding additional moisture (plus biotic condensation nuclei) to trigger rain sooner and more often than it would otherwise occur, thus milking the sky. Thus, rain recycling continually milks moisture from the atmosphere. The more water (and therefore life) in the system, the better it can do this. You've said, if I understand correctly, that rain recycling isn't enough to increase moisture in an area, that only the biotic pump can do this. Can you explain the difference between rain recycling and the biotic pump in this respect.
2. The Lakota, like many indigenous, say "water is life." One thing the equations don't explicitly mention is the amount of water stored in living matter. And that basin is dynamic, alive and growing, which seems like it might complicate the math.
Like everybody, I wonder if (given the real error margin of measurements), even the multiplication by 20 years as suggested by Anastassia of the minute differences in evapotransiration, precipitation and water availability quoted in that study makes sense. Anastassia's analysis is more interesting than the original study.
I like the idea of considering processes from different angles (from the land and from the atmosphere) to reach different perspectives and also, not least, to avoid direct confrontations that sometimes could break dialogue. On the other hand, it is really useful to underline exactly were things start to change...
In this context, last September, I found myself in the Amazon, teaching ecohydrology to Ecuadorian students . One night, Q=P-E (where Q is river discharge) easily became a stumbling block for a huge controversy, because if you consider that P is independent of what happens down on the ground and if you add trees and increase E, then Q must decrease. This equation is telling somehow: let’s cut the forest and collect more water! This is an old controversy with hydrologists and foresters all over the world, and you have often written about it.
Then, it came to my mind that what the Biotic Pump is telling us, in this context, could be tentatively represented like: Q = P-E+C(fE); where convergence C is somehow related to E (or rather to the forest-Evapotranspiration part of it). Of course, this would assume storage steady-state.
This way of addressing the issue really shocked some of the students, because it challenged the fundamentals of what is in their hydrology textbooks (Q=P-E). So, it served my purpose: I was asking them to close the books and look up above their heads.
In the end, I think that the challenge you are proposing to us is to think "differently", in parallel to the textbooks, by developing new concepts and new categories. Your work changes physics narratives and the "what if" metaphores associated to them that we learnt in school. I feel I need to find the points of divergence to reconnect the dots.
Thank you for inspiring us and accompanying us in understanding a little more every day.
Another very stimulating article. Measuring rainfall P, is almost a lost cause. In our farming community, we all keep rainfall records and we all marvel at the fact that, in some years, one farmer might record 1200mm of rain while another (15kms away) only records 400. But our sample rate is approximately 1 in a billion (a single rain-gauge for a 1000ha farm). Any statistic based on such a low sampling rate is meaningless, ESPECIALLY for a parameter with as much variability as rainfall.
The disappointing thing from that analysis of the Chinese efforts to re-green their environment (and so their rainfall) was that the increase was only 1.24mm/year - after a greater than 16% increase in leaf cover. That seems very disappointing. However, the Climate IS non-linear, so perhaps a 25% increase in leaf cover will suddenly produce a 50mm/year increase in rainfall.
What is encouraging is that both China and India, two of the most densely populated countries on Earth have both managed to increase their leaf cover by > 16%. If they can do it, then we all can.
Don't forget that, from an Agricultural perspective, it is not just the total amount of rain, but the length of the growing season, that is very important. Trees can, if they can still access sufficient moisture through their roots (from a water table that has not been sucked too low) initiate rainfall earlier in the season, and sustain it longer into the dry season, than any other vegetation cover. (A phenomenon that you have mentioned has been demonstrated in South America.)
I am sorry that I won't be able to attend your discussion tomorrow. I hope a recording will be available on You Tube afterwards.
Keep well,
Bruce
Hello, Bruce, "the increase was only 1.24mm/year" reflects some confusion in reporting the units. Precipitation is measured in mm/year, but sometimes per year is omitted as if it is self-evident. Then trends in precipitation, which should be in mm/year/year (i.e., how a flow measured in mm per year changes per year) becomes simply mm/year. In reality, after reading the paper, it becomes clear that here they talk about a trend, which in 20 years of re-greening would result in an additional precipitation of 20+ mm/year.
But there is much more to this story, stay tuned!
You are right, a trend of 1.24mm/year/year IS worth getting excited about, but then it begs the question as to when will that trend level off? Rainfall in China is unlikely to increase indefinitely . . . . . but no doubt you will discuss that at some time in the future.
HI Anastasia, I made a note earlier about the devastating impact of the 2015 El Nino and the dramatic drop in global above ground water storage which has not recovered. the point being that the massive die off of tropical trees and the time it takes to regrow have very long lasting effects which is what I think the graphs are really showing which also have altered cloud mass, Wm2 and associated albedo. the graphs are included in this note
https://substack.com/@tcrethers/note/c-225930351
One then could reason is that the water availability is just locked in the above ground vegetation that is obviously increasing.
I also did a quick analysis of the impact of spreader levees on flat semi arid areas of the world with this in mind and the results of being able to change the available water coefficient into vegetation and ground water recharge were remarkable. Instead of up to 90% loss from hydrophobic soils, spreader levees can change this to under 50% and rehydrate areas down stream that do not even receive any rainfall. This is currently being trialed in Australia and I made a post from a quick AI analysis online for anyone to look at.
https://substack.com/home/post/p-193742674
https://substack.com/home/post/p-193632133
Thank you, Anastassia, for explaining so clearly how the measurements necessary to the task of determining fluxes of water into and out of an area are undertaken, and how complicated and uncertain they inherently are.
This places all of our endeavors towards understanding in an important real-world-science context. It is not just word-problems.
Thanks for this, Anastassia. It helps demystify some of this basic hydrology.
A couple things puzzle me.
1. Millan Millan believed "water begets water." Part of how he saw this happening was by land milking the atmosphere, which it did by adding additional moisture (plus biotic condensation nuclei) to trigger rain sooner and more often than it would otherwise occur, thus milking the sky. Thus, rain recycling continually milks moisture from the atmosphere. The more water (and therefore life) in the system, the better it can do this. You've said, if I understand correctly, that rain recycling isn't enough to increase moisture in an area, that only the biotic pump can do this. Can you explain the difference between rain recycling and the biotic pump in this respect.
2. The Lakota, like many indigenous, say "water is life." One thing the equations don't explicitly mention is the amount of water stored in living matter. And that basin is dynamic, alive and growing, which seems like it might complicate the math.
All best,
Rob
Like everybody, I wonder if (given the real error margin of measurements), even the multiplication by 20 years as suggested by Anastassia of the minute differences in evapotransiration, precipitation and water availability quoted in that study makes sense. Anastassia's analysis is more interesting than the original study.
Thank you Anastassia for this.
I like the idea of considering processes from different angles (from the land and from the atmosphere) to reach different perspectives and also, not least, to avoid direct confrontations that sometimes could break dialogue. On the other hand, it is really useful to underline exactly were things start to change...
In this context, last September, I found myself in the Amazon, teaching ecohydrology to Ecuadorian students . One night, Q=P-E (where Q is river discharge) easily became a stumbling block for a huge controversy, because if you consider that P is independent of what happens down on the ground and if you add trees and increase E, then Q must decrease. This equation is telling somehow: let’s cut the forest and collect more water! This is an old controversy with hydrologists and foresters all over the world, and you have often written about it.
Then, it came to my mind that what the Biotic Pump is telling us, in this context, could be tentatively represented like: Q = P-E+C(fE); where convergence C is somehow related to E (or rather to the forest-Evapotranspiration part of it). Of course, this would assume storage steady-state.
This way of addressing the issue really shocked some of the students, because it challenged the fundamentals of what is in their hydrology textbooks (Q=P-E). So, it served my purpose: I was asking them to close the books and look up above their heads.
In the end, I think that the challenge you are proposing to us is to think "differently", in parallel to the textbooks, by developing new concepts and new categories. Your work changes physics narratives and the "what if" metaphores associated to them that we learnt in school. I feel I need to find the points of divergence to reconnect the dots.
Thank you for inspiring us and accompanying us in understanding a little more every day.
Nic