LWF-Brook90

The LWF-Brook90 model (Hammel and Kennel, 2001) simulates the water balance of a forest site. It calculates the individual components of evaporation and water flows in the soil. The model has been used internationally for many years and is also used in Germany by the state forestry research institutes for site-specific water balance calculations to estimate water flows, soil moisture, and drought stress for forest sites. LWF-Brook90 is based on the Brook90 model (Federer, 2002; Federer et al., 2003) and was modified and expanded at the Bavarian State Institute for Forestry and Forest Management (LWF) (DWD).

Parameter Overview

General abbreviations

• yr = Year
• mo = Month
• da = Day
• doy = Day of year
• ti = Transpiration index (current transpiration / potential transpiration), analogous to STRES

l2_abovann (annual above ground water)

• rfal = Rainfall rate [mm/d]
• rint = Rainfall catch rate [mm/d]
• sfal = Snowfall rate [mm/d]
• sint = Snowfall catch rate [mm/d]
• rsno = Rain added to snowpack [mm/d]
• rnet = Rain reaching soil surface [mm/d]
• smlt = Melt drainage rate from snowpack [mm/d]
• slfl = Input rate to soil surface [mm/d]
• srfl = Source area flow rate [mm/d]

l2_beloann (annual below ground water)

• nl = Number of soil layers to be used
• infl = Infiltration rate into layer [mm/d]
• byfl = Bypass flow rate from all layers for iteration [mm/d]
• tran = Average transpiration rate from layer [mm/d]
• slvp = Evaporation rate from soil [mm/d]
• vrfl = Vertical matrix drainage rate from layer [mm/d]
• dsfl = Downslope flow rate from all layers for iteration [mm/d]
• ntfl = Net flow rate into layer [mm/d]

l2_budgann (annual budget)

• prec = Precipitation rate [mm/d]
• mesfl = Measured streamflow for the date [mm]
• flow = Total streamflow [mm]
• evap = Evapotranspiration [mm]
• seep = Seepage loss [mm]
• snow = Snowpack water equivalent [mm]
• swat = Total soil water in all layers [mm]
• gwat = Groundwater storage below soil layers [mm]
• intr_s = Intercepted rain and snow (initial value) [mm]

l2_bugday (daily budget)

Analogous to l2_budgann

l2_calcday

• ti = see section general
• awat200 = Total available soil water at depth 200 cm [mm]
• awat40 = Total available soil water at depth 40 cm [mm]
• wetness200 = Wetness as fraction of saturation at depth 200 cm
• wetness40 = Wetness as fraction of saturation at depth 40 cm
• wetness40 = Wetness as fraction of saturation at depth 60 cm

l2_climate_in (climatic inputs)

• tmax (input variable) = Maximum temperature for the day [°C]
• tmin (input variable) = Minimum temperature for the day (input parameter) [°C]
• vappres (input variable) = Vapour pressure for day [kPa]
• wind (input variable) = UW: Daily mean wind speed at 10 m above ground [m/s]
• prec (input variable) = PRECIN: Daily precipitation [mm]
• globrad (input variable) = SOLRAD: Solar radiation for the day on a horizontal surface [MJ/m²]
• sunhours = Sunshine duration hours
• densef (fixed parameter) = Canopy density multiplier
• height = Canopy height [m]
• lai = Projected leaf area index [m²/m²]
• sai = Projected stem area index [m²/m²]
• age = Stand age in years

l2_evapann (annual evaporation)

• mesfl = Measured streamflow for the date [mm]
• flow = Total streamflow [mm]
• evap = Evapotranspiration [mm]
• tran = Average transpiration rate from layer [mm/d]
• irvp = Evaporation rate of intercepted rain [mm/d]
• isvp = Evaporation rate of intercepted snow [mm/d]
• slvp = Evaporation rate from soil [mm/d]
• slvp = Evaporation rate from soil [mm/d]
• snvp = Evaporation rate from snowpack [mm/d]
• pint = Average potential interception rate [mm/d]
• ptran = Average potential transpiration rate for day [mm/d]
• pslvp = Potential soil evaporation rate [mm/d]

l2_evapday (daily evaporation)

Analogous to lf_evapann

l2_flowann (annual flow)

• mesfl = Measured streamflow for the date [mm]
• flow = Total streamflow [mm]
• seep = Seepage loss [mm]
• srfl = Source area flow rate [mm/d]
• slfl = Input rate to soil surface [mm/d]
• byfl = Bypass flow rate from all layers for iteration [mm/d]
• dsfl = Downslope flow rate from all layers for iteration [mm/d]
• gwfl = Groundwater flow to streamflow rate [mm/d]
• vrfln = Vertical matrix drainage rate from lowest layer [mm/d]

l2_miscday

• vrfln = Vertical matrix drainage rate from lowest layer [mm/d]
• safrac = Source area fraction
• stres = Transpiration (TRAN) / Potential transpiration (PTRAN) for time period
• adef = Available water deficit in root zone [mm]
• awat = Total available soil water in layers with roots [mm]
• relawat = Relative available soil water in layers with roots
• awat40 = Total available soil water at depth 40 cm [mm]
• nits = Number of iterations in precipitation interval
• balerr = BALERD: Error in water balance [mm]

l2_swatday

• nl = Number of soil layers to be used
• swati = Soil water volume in layer [mm]
• theta = Water content [mm_water / mm_{soil matrix}]
• wetnes = Wetness, fraction of saturation
• psimi (initial value) = Matric soil water potential for layers [kPa]
• psiti = Total soil water potential for a layer [kPa]