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Soil Water Balance

Source: R/calcWatBal.R
calcWatBal.Rd

Function to estimate a budget-based daily soil water balance. It calculates the amount of water present in the root zone of a homogeneous grass canopy growing on a well-drained and homogeneous soil.

Usage

calcWatBal(data, soilWHC)

Arguments

data

a dataframe containing the required variables: Columns must contain the following parameters:

   Lat: latitude of the site in decimal degrees.
   Lon: longitude of the site in decimal degrees.
   Elev: elevation above sea level in (meters).
   Year: year of record "YYYY".
   Month: month of record "MM".
   Day: day of record "DD".
   Rain: daily rainfall in (mm).
   Eto: daily potential evapotranspiration in (mm).

soilWHC

Water holding capacity of the soil in (mm).

Value

The function generates a data frame containing the following components:

DRAIN: amount of deep drainage in (mm).

TRAN: amount of water lost by transpiration in (mm).

RUNOFF: surface runoff in (mm).

AVAIL: available soil moisture storage in (mm).

R: actual-to-potential evapotranspiration ratio.

References

Allen, R.G.; Pereira, L.S.; Raes, D.; Smith, M. Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements; FAO Irrigation and Drainage Paper no. 56; FAO: Rome, Italy, 1998; ISBN 92-5-104219-5.

Doorenbos, J. and Pruitt, W.O. 1975. Guidelines for predicting crop water requirements, Irrigation and Drainage Paper 24, Food and Agriculture Organization of the United Nations, Rome, 179 p.

See also

calcEto, calcSeasCal

Examples


# \donttest{
# load example data:
data(AgroClimateData)

# Estimate daily PET:
PET <- calcEto(AgroClimateData, method = "PM", Zh = 10)

# Add the estimated PET 'ET.Daily' to a new column in AgroClimateData:
AgroClimateData$Eto <- PET$ET.Daily

# Estimate daily water balance for the soil having 100mm of WHC:
watBal<- calcWatBal(AgroClimateData, soilWHC = 100)

# Visualizing water balance parameters for 2019/20 season
watBal.19T20 <- watBal[watBal$Year %in% c(2019, 2020),]
date.vec <- as.Date.character(paste0(watBal.19T20$Year, "-",
                                     watBal.19T20$Month, "-",
                                     watBal.19T20$Day))

plot(y = watBal.19T20$AVAIL, x = date.vec, ty="l", col="black", xlab="",
ylab=" Water (mm)",
       main="Daily Water Balance Parameters", lwd = 1, lty = 2)
 lines(y = watBal.19T20$Eto, x = date.vec, col="red", lwd = 3, lty = 1)
 lines(y = watBal.19T20$Rain, x = date.vec, col="blue", lwd = 1, lty = 1)

  legend("bottomright",c("Rain","Eto","Available Moisture"),
        horiz=FALSE, bty='n', cex=1.2,lty=c(1,1,2),lwd=c(1,3,1),
        inset=c(0,0.7),
        xpd=TRUE, col=c("blue","red","black"))

# }