Blog entry 3:

Water form precipitation falls through the canopy on the ground. A certain amount of this water doesn’t penetrate the canopy due to interception. The aim of the following methods is to measure interception as simple as possible and as exact as possible. The interception loss gets easily calculated by the difference between the irrigated water and the water which falls on the ground. To measure that, the water below the canopy needs to get collected by a vessel. Former studies used plastic sheets (Shuttleworth et al., 1984)

Plants at the tree nursery Schinznach get irrigated by two different irrigation systems. One is sprinkler irrigation and the other is a dripping system. Due to the fact that water irrigated from a dripping system doesn’t touches leaves of the plants and therefore doesn’t cause interception, it will not be taken into account for the further studies.

There are two different methods to measure. The first one measures the interception per plant. The plant gets irrigated by a certain amount of water. The vessel collects the through-falling water. The difference of the amounts is the result. It is easily feasible to implement that in a potter. Another method is to irrigate two areas equally, one with plants the other without. Under the plants is one vessel and where no plants are is the second one. Then afterwards, the amount of water within the vessels gets compared. Due to the fact that the sprinkler system doesn't irrigates all plants in its environment equally, it is hardly possible to get to know the irrigated amount of water at a specific square meter. Therefore, the second method would be the better option to implement on the field.

The amount of the interception loss depends on the species, therefore, the measurements must be implemented at multiple species. However, it is not possible to do this with all different species from the tree nursery.

The only required material we need is vessels and plastic sheets. Water and irrigation devices are already at the tree nursery.

These methods don’t need a lot of time to implement. In one day should be feasible. Firstly, the plants get irrigated. After a while (depending on the weather), when the intercepted water is evaporated, the amount of water in the vessel can be measured. To measure the run off by Valerio, plants need to get irrigated of course. Meanwhile interception can be measured. Therefore, the measurements of interception depends on the run off measurement.

The amount of intercepted water depends strongly on the weather. The bigger the air moisture, the more time the water takes to evaporate. Therefore, it is very difficult to presume how long it takes.

There is not much additional information needed apart form information about the irrigation, such as length, amount and frequency.

The result of these measurement tells us how much water get lost by evaporation after irrigation or precipitation. It is a part of the whole evapotranspiration rate. This helps us to get to know more about the whole water cycle.

Bibliography

Shuttleworth, W. J., Gash, J. H. C., Lloyd, C. R., Moore, C. J., Roberts, J., Filho, A. D. O. M., … Carvalho De Moraes, J. (1984). Eddy correlation measurements of energy partition for Amazonian forest. Quarterly Journal of the Royal Meteorological Society, 110(466), 1143–1162. http://doi.org/10.1002/qj.49711046622

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. 

Abbildung 1: Li-6400XT of Licor (www.licor.com)

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). 1

Blog entry 1:

What is the impact of a higher interception on evapotranspiration and the final water use? Is interception diminishable?

Due to climate change and therefore rising temperature, water is going to be more and more the limited factor for plant growth. This urges people to be more sensitive at dealing with water. By minimising transpiration and evaporation water loss is getting reduced a lot. Another way to deal with that problem is to decrease the runoff (Prosdocimi et al., 2016). However, up to half of the water loss is on the account of the evaporation from water of wet canopy (van Dijk et al., 2015). To reduce this interception loss, plantations in Japan get thinned because, according to Tsukamoto, 1998 and Kuraji, 2003, found in Shinohara et al. 2015, the repellency of precipitation and therefore the interception of unthinned plantations is higher. This causes reduced runoff on a short-term and water loss. Furthermore, drops falling from canopy cause often more soil erosion than open rainfall as a result of their higher kinetic energy (Zhou et al., 2002 and Nanko et al., 2004 found in Shinohara et al., 2015). These drops disaggregate the soil structure which leads to a lower infiltration rate and therefore to more runoff on a long-term and a higher evaporation rate.

The tree nursery Zulauf Ag irrigates its plants with water from a pont. This water flues back into the pont again. Despite of this sophisticated circulation, the tree nursery needs to buy a lot of additional water. An option to decrease the amount of bought water could be to diminish the amount of evaporation of Intercepted water. This leads to the following questions:

Is interception at the tree nursery Zulauf Ag measureable? Does a higher interception loss make a big difference to water? Is there an opportunity to reduce interception at Zulauf Ag?

Prosdocimi, M., Jordán, A., Tarolli, P., Keesstra, S., Novara, A., & Cerdà, A. (2016). The immediate effectiveness of barley straw mulch in reducing soil erodibility and surface runoff generation in Mediterranean vineyards. The Science of the Total Environment, 547, 323–30. http://doi.org/10.1016/j.scitotenv.2015.12.076

Shinohara, Y., Levia, D. F., Komatsu, H., Nogata, M., & Otsuki, K. (2015). Comparative modeling of the effects of intensive thinning on canopy interception loss in a Japanese cedar (Cryptomeria japonica D. Don) forest of western Japan. Agricultural and Forest Meteorology, 214-215, 148–156. http://doi.org/10.1016/j.agrformet.2015.08.257

van Dijk, A. I. J. M., Gash, J. H., van Gorsel, E., Blanken, P. D., Cescatti, A., Emmel, C., … Wohlfahrt, G. (2015). Rainfall interception and the coupled surface water and energy balance. Agricultural and Forest Meteorology, 214-215, 402–415. http://doi.org/10.1016/j.agrformet.2015.09.006