1 / 14

Transpiration

The Water Balance. Rainfall. Transpiration. Evaporation. Irrigation. Runoff. Root zone. Drainage. Apsim is a one dimensional model. Two methods of water movement: Tipping bucket ( SoilWater ) Richards Equation (SWIM). Rainfall.  SW = Inputs - Outputs

mliss
Download Presentation

Transpiration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Water Balance Rainfall Transpiration Evaporation Irrigation Runoff Root zone Drainage

  2. Apsim is a one dimensional model. • Two methods of water movement: • Tipping bucket (SoilWater) • Richards Equation (SWIM)

  3. Rainfall • SW = Inputs - Outputs • SW = (R + I) – (Et + Es + RO + D) • Where: • SW – Change in daily soil water • R – Rainfall • I – Irrigation • Et – Transpiration • Es – Evaporation • RO – Runoff • D - Drainage Runoff Et Es Infiltration Soil horizon 1 Soil horizon 2 … Drainage

  4. Bucket size Saturated Drained Upper Limit (aka Field Capacity) Lower Limit (15 bar) Air Dry (oven)

  5. SoilWater

  6. SoilWater: Runoff and Infiltration USDA curve number (CN) runoff model

  7. SoilWater: Runoff and Infiltration Modified USDA curve number runoff model Q = runoff (mm), P = rainfall (mm), S is the retention parameter (mm), derived from - Antecedant soil water content (to 450mm), - Curve Number, - Bill Mockus’ 1954 hand drawn AMC charts

  8. SoilWater: Runoff and Infiltration Modified USDA curve number runoff model CN starts at CN2bare, reduced to CNred when cover reaches CNcov.

  9. SoilWater: Saturated Flow ∆SWi+1= SWCONi x (SWi - DULi); for layer i, SWi > DULi

  10. SoilWater: Soil Water Evaporation Water in surface layer may dry down to air-dry water content. Potential evaporation (Eo) is from Priestly-Taylor Eo = f(temperature, radiation, albedo,cover) Actual evaporation is a two stage drying process. - during first stage = potential (ie. eos), until ∑Es = U - during second stage = CONA * √t

  11. SoilWater: Soil Water Evaporation Can change between summer & winter.

  12. SoilWater: Transpiration Plants can extract water to a crop-specific Lower Limit (LL). This LL can represent root distribution, and/or soil constraints.

  13. SoilWater: Transpiration The potential daily rate of extraction is: ∆sw= -kl x (sw – ll) kl is the fraction of available water that can be extracted per day.

  14. SoilWater: Root Development Root development (growth) can be modified by XF – it represents a “exploration factor” for root growth in a layer. A value of 0 stops growth in that layer.

More Related