Blog entry 2:
Interception
is close connected to transpiration. Generally, the intercepted water gets lost
mostly because it doesn’t seep into the ground but stays at the surface of the
leaf and gets evaporated. Therefore the water loss is due to the eventual
evaporation.
Methods
The interception
loss of irrigated water is usually measured by subtracting the rainfall below
the canopy form the rainfall above the canopy (Lazerjan,
2015). Another way to quantify evaporation
is to subtract transpiration from evapotranspiration (Odhiambo
& Irmak, 2015) or to compare the run off and the
seeped water with the original irrigated water. However, to measure the
evaporation, it is important to ensure that the evaporation from the ground is
excluded.
A method to measure the transpiration is the Li-6400XT
of Licor (“LI-6400XT
Portable Photosynthesis System - LI-COR Environmental,” n.d.). The advantages is that the
measurement is right on the leaf. This device is used for measuring photosynthesis
and also the concentration of CO2 and the of transpiration. By
subtracting transpiration rate from evapotranspiration rate, we get evaporation
rate. This evaporation rate still consists of leaf and ground evaporation.
 |
A
possibility way to measure the run off is to irrigate potters in two different
ways. On way is from above upon the canopy and the other way is directly upon
the ground of the potter. Eventually,
the amount of water which flows through the potter into a vessel will be
compared. The difference between these two methods is probably
because of the evaporated water from the leaves. It is supposed that the vessels of on-ground-irrigated potters will
catch more water. However, this methode should be implement with various
periods of time of irrigation. It could make a difference whether the
irrigation rate is small but during the whole day constant or whether the
plants get irrigated only a few times a day with a bigger amount of water.
Results
The Li-6400XT gives us the amount of water containing in the air. The results of the run off-methode will show basically
whether there is a difference of the amount of water or not. The evaporation and therefore the size of the difference is due to the different temperature
and air humidity during the whole year probably very erratic. Measuring in just
one week is too short to get results on a big scale.
Bibliography
Lazerjan, M.
S. (2015). First attempt to measure rainfall canopy interception loss,
throughfall, and stemflow in Juglans regia Linn and Cup. Sempervirens L. Var.
fastigiata in the north of Iran. Laurier Institute for Water Sciences, 9,
60–78. Retrieved from
https://www.mendeley.com/research/first-attempt-measure-rainfall-canopy-interception-loss-throughfall-stemflow-juglans-regia-linn-cup/?utm_source=desktop&utm_medium=1.16.1&utm_campaign=open_catalog&userDocumentId={34290f73-466d-413c-b069-bada6ac8d456}
LI-6400XT
Portable Photosynthesis System - LI-COR Environmental. (n.d.). Retrieved April
8, 2016, from https://www.licor.com/env/products/photosynthesis/LI-6400XT/
Odhiambo, L.
O., & Irmak, S. (2015). Relative Evaporative Losses and Water Balance in
Subsurface Drip and Center Pivot–Irrigated Soybean Fields. Journal of
Irrigation and Drainage Engineering, 141(11), 04015020.
http://doi.org/10.1061/(ASCE)IR.1943-4774.0000907
Table of
figures
Abbildung 1:Li-6400XT of Licor
(www.licor.com)
Dear Christoph
AntwortenLöschenI like the Idea of measuring the interception to estimate how much water gets lost through the sprinkler irrigation. I think with the dripping system there is no relevant interception, only when it is raining.
You wrote about subtracting the the rainfall below the canopy form the rainfall above the canopy. To measuring the interception, Shuttleworth et al. (1984), Calder et al. (1986) and Calder (1990). give a more specified method description about this process. They covered the floor with plastic sheets and collected the through fall. This amount was subtracted from the irrigation amount. You can read more about this in the paper which is mentioned in the bibliography.
Did you check if we have access to the Li-6400XT?
If yes, this would be a very helpfully tool to complete the water balance by the transpiration amount and I would like to work with it.
Best regards
Eline
Bibliography:
Shuttleworth, W. J., Gash, J. H. C., Lloyd, C. R., Moore, C. J., Roberts, J. M., et.al, 1984. Eddy correlation measurements of energy partition for Amazonian forest. Quarterly Journal of the Royal Meteorological Society 110, 1143–1162.
There is at least one Li-6400XT at the zhaw. I haven't asked yet whether we can borrow it.
AntwortenLöschenDear Christoph,
AntwortenLöschenI like your research question very much as the potentially avoidable interception could lead to significantly less water consumption.
In your Method description you mention that to measure evaporation (which is comparable to interception) it is important that the evaporation from the ground is excluded, but you don’t indicate how to do it. For instance, you present the Li-6400XT and then precise that the measured evaporation rate still consists of leaf and ground evaporation.
As an advantage of the Li-6400XT you mention that the measurement is right on the leaf, have you cheeked weather it works also on small leaves or with coniferous plants?
In the results you mention that the obtained data will not permit a focus on a whole year. I agree with that; therefore, I would keep the focus on just a week.
As far as I know other tree nurseries use primarily the dripping system which leads to less interception. At our site visit Mr. Zulauf told us that they use the sprinkler system mainly because of the dirty water from the pond which obstruct the small tubes of the dripping system. In this optic I would find it interesting if you also think of a way to filter the water in order to make the pond water suitable for the dripping system.
Best regards,
Valerio
Dear Christoph,
AntwortenLöschenYour research question will make a very interesting complement to the other water balance research questions. Particularly as some of your team members will investigate the water cycles including evaporation measurements, a collaboration could help to get interesting data even if its only a week we will be doing the research.
Subirrigation systems are very common in tree nurserys because they are easy to install and relatively cheap. an interestimg additional question concerning your topic could be, if the economisations equate the disadvantages of increased runoff and its consequences compared with less interception causing sprinkler systems,maybe also including the dripping system combined with water filters mentioned by valerio.
Have you already decided on which plant types and with which testing system your reseach done within only one week would be the most significant?
Best Regards,
Zoë
Dear Christoph
AntwortenLöschenI agree with you, that interception is an important factor of the water balance we will investigate. I also agree, with the methods, based on the difference of rainfall or irrigated water above and below the canopy. But the instrument you propose to use will eventually not help much to solve the problem, because you will measure photosynthesis instead of transpiration. Or is it possible to measure both? If this is true, you could compare the transpiration with the independently measured evapotranspiration. To quantify interception, I would focus primarily on the classical method with a good experimental design.
Best regards
Luzi