The Nash–Sutcliffe coefficient of efficiency BIBU 1361 computed as:equation(7)ENS=1−∑i=1nQi,s−Qi,m2∑i=1nQi,m−Q¯m2where, Qi,s is simulated quantity (flow or TSS), Qi,m is measured quantity and Q¯m is mean of the measured quantity.
For p-factor the 95 % prediction uncertainty (95PPU) is calculated at the 2.5% and 97.5% levels of the cumulative distribution of an output variable obtained through Latin hypercube sampling. The average distance d¯ between the upper and the lower 95PPU is dicots used to calculate the r-factor expressed as (Abbaspour, 2008):equation(8)r‐factor=d¯XσX.
Uncertainty is an inherent characteristic of hydrologic models. These uncertainties should be properly addressed and quantified for the models to be usable in decision making. In SUFI-2 a measure, p-factor is used to quantify the degree to which all uncertainties are accounted. The p-factor is the percentage of measured data bracketed by the 95% prediction uncertainty (95PPU) (Abbaspour, 2008).