Where
\(\overset{\overline{}}{R}\) is mean annual rainfall of previous years (mm)
\(\mu\) is the standard deviation of mean annual rainfall
\(t_{50+p}\) is t-value at 50 + p per-cent probability level
\(R_{p}\) is expected annual rainfall at probability, p (mm)
PET is potential evapotranspiration
\({R^{\prime}}_{p}\) is effective annual rainfall at probability p (mm)
\(\text{RO}_{p}\) is annual runoff at probability p (mm)
\(\text{AE}_{p}\) is actual annual evapotranspiration at probability p (mm)
K is available water holding capacity at probability p (mm) = 233 mm
Determination of total forage Forage supply of the rangeland
If \(\text{AE}_{p}\) < 29 mm: \(\text{TDM}_{p}\) = 0 …………………………………………………Equation 5
If \(29\ mm\ \leq\ \text{AE}_{p}\leq 263\ mm\):
\(\text{TDM}_{p}=(3.32*\left(\text{AE}_{p}-29\right)*(1.613\ \pm 0.613*\left(\frac{F-1}{125}\right)^{0.5})\)…………….Equation 6
If \(\text{AE}_{p}\ >263\ mm\):
\(\text{TDM}_{p}=(777+6.26*\left(\text{AE}_{p}-263\right)*(1.613\ \pm 0.613*\left(\frac{F-1}{125}\right)^{0.5})\)…Equation 7
NB: If F-1 > 0, use positive value for \(\pm\) while use negative value if F-1 < 0