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The equations used for runoff calculations are presented in Table 2 whilst the values for the parameters in Equation 1 are presented in Table 3. Table 2 - Equations for the Calculation of Pesticide Runoff L%runoff = (R/P) × Crsoil_surface × f1slope × f2bufferzone × f3foliar_application × heterogeneity_factor × 100 + suspended_pesticide; (Equation 1). f1slope = 0.02153 × slope + 0.001423 × slope2; where slope is expressed as % (Equation 2). Crsoil_surface = e(-3 ln2/DT50) × (1/(1+Kd)); for three days of degradation (Equation 3). f3foliar_application = (1 - Fret); (Equation 4) where Fret is fraction of pesticide retained by crop and is assumed to be 50% of the fraction intercepted by the crop (Fint). Table 3 - Values for the Parameters in Equation 1 Parameter Value R (The daily quantity of runoff water) 20 mm (default value) P (The daily precipitation) 100 mm (default value) Crsoil_surface (Concentration reduction factor based on the environmental fate of the pesticide in soil) For Tier 1, Crsoil_surface = 1 Calculated value for Tier 2 & Tier 3 (Equation 3) f1slope for steep slopes > 12.5% - < 20% (>7° - <11°) 1 f1slope for ordinary slopes > 4% - ≤ 12.5% (> 2° - ≤ 7°) 0.5 (default value) f1slope for gentle slopes ≤ 4% (≤ 2°) 0.1 f2bufferzone (Represents the reduction of pesticide in runoff water due to buffer zones) 1 (default value) f3foliar_application (The amount of foliar applied pesticide available for runoff.) Calculated (Equation 4) f3foliar_application (When pesticide is applied to bare soil or weeds no foliar interception occurs; Fint = 0) 1 Heterogeneity factor 0.5 (default value) Suspended pesticide 0 (default value) Volume of water in the edge of field runoff 200,000 L/ha Volume of water in a standard water body for Tier 3 calculations on a 1 ha field 1500 m3 (Tier 3)