3. Rainfall LossesKind of losses:1. Interception, 2. Depression storage, 3. Evaporation, 4. Transpiration, 5. Evapotranspiration, 6. Infiltration.
3.1-2. Interception and depression storageKind of initial losses
1. Caught by leaf of vegetation →
interception → evaporate, stem-flow, through fall. 2. Depression storage →
evaporate,
infiltration, overflow, → depend on: soil type, soil moisture, catchment slope, surface condition.
3.3. EvaporationPerubahan air (liquid → masa air) menjadi uap air (gas) → temperatur, tekanan uap, angin, tekanan udara, berat satuan air, panas tersimpan dalam air → terjadi setiap saat. Diukur dengan Pan Evaporation (Class A EP, Collorado
3.4. TranspirationPelepasan air dari tubuh tanaman → air diambil dari akar dan dilepas melalui daun untuk kebutuhan hidup tanaman tersebut, → terjadi hanya pada siang hari. Faktor yang mempengaruhi: jenis tanaman (jenis
3.5. EvapotranspirationPelepasan air dari tubuh air (evaporation) dan tanaman (transpiration) pada waktu yang bersamaan → consumptive use. Jenis: PET (Potential Evapotranspiration), AET (Actual Evapotranspiration). PET →jumlah air
tidak terbatas, AET → jumlah air terbatas. Istilah yang sangat terkait dengan ET: field capacity(kapasitas lapang) and permanent wilting point (titik layu)
Alat ukur ET1. Lysimeter → tangki khusus yang berisi tanah dan jenis tanaman tertentu. 2. Field Plots:
ET = P + IR – RO –Gs ±ΔS P = precipitation, IR = Irrigation input, RO
iummary of equations for calculating evaporation*
(1) Energy balance method _
E, (10353112n (mm/day)Where
Rn = net radiation (W/mz)
(2) Aerodynamic method
Ea =B(eals _ ea) (mm/day)
u; is wind velocity (m/s) measured at height 22 (cm), and zu is from Table 2.8.2. Also,
T: air temperature (°C)
ea :Rheas in which R,, is the relative humidity (0 E R,, S 1).