1. Lecture 5 - 1 ERS 482/682 (Fall 2002) Interception ERS 482/682 Small Watershed Hydrology

2. Lecture 5 - 2 ERS 482/682 (Fall 2002) Definition Amount of gross precipitation that is captured by vegetation or surface cover and is evaporated back to the atmosphere

3. Lecture 5 - 3 ERS 482/682 (Fall 2002) Precipitation movement through canopy Throughfall: movement through spaces between leaves or dripping Stemflow: runs down stems and trunks Evaporation from canopy and litter Figure 3-1: Dunne & Leopold (1978)

4. Lecture 5 - 4 ERS 482/682 (Fall 2002) Interception Depends on: –Vegetation type and density See Table 7-8 (Dingman 2002) –Storm characteristics See Figure 3-2 (Dunne & Leopold 1978) Snow interception tends to be << rainfall interception –Season of the year Snow or rain Variation in sunlight and heat See Tables 3-2 and 3-3 (Dunne & Leopold 1978)

5. Lecture 5 - 5 ERS 482/682 (Fall 2002) Net precipitation, Rn Figure 7-15: Dingman (2002)

6. Lecture 5 - 6 ERS 482/682 (Fall 2002) Measuring interception Measure gross rainfall, throughfall, stemflow  solve for canopy loss Figure 7-15: Dingman (2002)

7. Lecture 5 - 7 ERS 482/682 (Fall 2002) Estimating interception Specific to location and land cover If enough local data: –Regression models (Table 7-7 in Dingman 2002) Viessman and Lewis (1996): L i = volume of water intercepted (in.) S = interception storage retained on foliage (0.01-0.05 in.) K = ratio of surface area of intercepting leaves to horizontal projection of area t = time (hr.) P = rainfall (in.)