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