Abstract
Hydrological properties of an area have been changed by the process of urbanization which results especially in increased runoff. Previous studies have suggested that rainfall interception by urban trees can reduce the runoff. The amount of intercepted rainfall depends on type of vegetation and on meteorological conditions which have the impact on reduction and retention of runoff which is important in urban areas. For four months, from 1st of April to 31th of July 2014, we had measured throughfall and stemflow under two deciduous trees (Betula pendula) and two coniferous trees (Pinus sylvestris) in center of Ljubljana, capital of Slovenia. Under each type of tree throughfall was measured with two trough gauges, one equipped with tipping bucket and one with manual 60 l tank to control automatically gathered data. There were also ten manual roving gauges which were randomly moved under the tree canopy. Stemflow was measured on one tree of each type with rubber collar fitted around the tree. The tube was connected to manually reading 20 l plastic tank. Data were collected after each event. Gross rainfall was measured using a tipping bucket rain gauge located on the clearing near the trees. During the measuring period we have detected 85 rainfall events with total depth of 488,3 mm. The average amount of gross precipitation per event was 5,7 mm and ranged from 0,2 mm to 57 mm. Throughfall events measured automatically with tipping bucket were grouped according to the dates of manually collected data and verified with weighted average of data collected with trough gage and roving gauges. Cumulative throughfall for birch (Betula pendula) was 280,5 mm with average value 6,0 mm per event and standard deviation of 7,31. Throughfall amount measured underneath pine (Pinus sylvestris) was 202,9 mm with an average value of 3,4 mm and standard deviation of 5,62. The total amount of stemflow for birch was 11,62 mm and for pine 0,72 mm. In case of birch stemflow was generated when the total rainfall exceeded 4,8 mm while the threshold depth of total rainfall for generating the stemflow on pine was 5,8 mm. Birch and pine have intercepted 40,2 % and 58,3 % of rainfall, respectively. The interception values suggest that coniferous trees in comparison with deciduous trees intercept more rainfall not only in winter time when deciduous trees are leafless but also in spring and in summer time. Possible parameters contributing to that are vegetative properties of coniferous trees which are thicker tree canopy, rougher bark and the slope of the branches away from the tree trunk. As result of those properties stemflow was much lower for pine in comparison with birch and can be even neglected.
FAQs
The interception values suggest that coniferous trees in comparison with deciduous trees intercept more rainfall not only in winter time when deciduous trees are leafless but also in spring and in summer time.
How is precipitation interception by trees? ›
During a rainfall event, precipitation is either intercepted by leaves, branches, and the trunk, or it falls directly through the tree to the ground. Intercepted water is stored temporarily on leaf and bark surfaces.
What is the interception of precipitation by vegetation? ›
When precipitation reaches the surface in vegetated areas, a certain percentage of it is retained on or intercepted by the vegetation. Rainfall that is not intercepted is referred to as throughfall. Water that reaches the ground via the trunks and stems of the vegetation is called stemflow.
What is the interception of the water cycle? ›
Interception is the process of interrupting the movement of water in the chain of transportation events leading to streams. The interception can take place by vegetal cover or depression storage in puddles and in land formations such as rills and furrows.
What is canopy interception in the hydrological cycle? ›
Canopy interception is the rainfall that is intercepted by the canopy of a tree and successively evaporates from the leaves. Precipitation that is not intercepted will fall as throughfall or stemflow on the forest floor. Many methods exist to measure canopy interception.
How do trees affect rainfall? ›
Plants and forests draw water out of the soil and exhale it into the atmosphere, impacting the balance of water and heat at our planet's surface, which fundamentally controls the weather. In some cases, such as in the Amazon rainforest, that water vapor can jumpstart precipitation.
What can precipitation be intercepted by? ›
Precipitation may first fall on a vegetation canopy that intercepts a portion of the precipitation. Surface depressions capture some of the precipitation reaching the ground and allow it to infiltrate. Water that does not infiltrate generally moves over the ground surface to become runoff volume.
Does deforestation increase interception? ›
Land Use Change: ● Deforestation(e.g. for farming) reduces interception, evapotranspirationand but infiltration increases (dead plant material in forests usually prevents infiltration). Construction reduces infiltration and evapotranspiration, but increases runoff.
What is precipitation interception and infiltration? ›
Interception occurs when precipitation is intercepted by surface features like vegetation and buildings before reaching the ground. Infiltration refers to water seeping into the soil or porous rock from the ground surface.
Why is interception important in the water cycle? ›
The most important role is as a rainfall reducer, causing a significant amount of rainfall to be directly fed back to the atmosphere which is not available for infiltration. Second, interception influences the spatial distribution of infiltration.
Interception is the capture and retention for the first 5mm of the rainfall resulting in no runoff. Interception and evaporation can account for 15-50% of yearly precipitation.
What is stormwater interception? ›
Not all of the precipitation which falls to a watershed reaches the soil surface to become available for plant growth, stream flow, or groundwater recharge. Interception is the process by which falling precipitation interacts with the vegetation covering a watershed.
What are the factors affecting interception? ›
Interception loss is invariably, greatest at the beginning of a storm, and then reduces with time. The most important factor, affecting interception loss, is the interception capacity of the vegetation cover, i.e., the ability of the vegetation to collect and retain the falling precipitation.
What is the difference between interception and throughfall? ›
Throughfall is the precipitation that penetrates through the canopy and reaches the soil surface by canopy drip. The amount of water retained by the canopy is termed interception (Interception = Precipitation - [Throughfall + Stemflow]).
What are the 7 steps of the water cycle? ›
- THE WATER CYCLE.
- EVAPORATION.
- CONDENSATION.
- PRECIPITATION.
- INTERCEPTION.
- INFILTRATION.
- PERCOLATION.
- TRANSPIRATION.
We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells and wet seasons. On the other hand, transpiration remains active during dry spells and dry seasons and is transported over much larger distances downwind, where it can act as a significant source of moisture.
How do plants play a role in precipitation? ›
Making Rain
In large forests, an enormous amount of water will transpire through leaves. In warm parts of the Earth, particularly near the Equator, plants create so much water vapor that they make their own weather! Rainforests rely on transpiration for most of their water.
Does planting trees increase precipitation? ›
But trees also release that water into the atmosphere in a process called transpiration, and the water eventually turns into rainfall—something other studies have pointed out. The result is that forests tend to dry out their local regions but increase the amount of rainfall in other places.
What is the interception loss of precipitation? ›
Interception loss is the portion of the precipitation that is returned to the atmosphere through evaporation from plant surfaces or is absorbed by the plant. It is the diffe- rence between the precipitation actually occurring over an area and the part that reaches the soil.
How does deforestation affect precipitation? ›
As more and more trees get cut down, evaporation levels are disrupted, drying up the moisture in the air and throwing off the balance of the water cycle. A continual cycle of dry air, low humidity, and decreased precipitation will inevitably lead to a drought-prone, desert-like climate.
