where l denotes seasons (l=1forwet season, l=2 for normal season);
p denotes type of groundwater (p=1 for alluvial aquifer and p = 2 for karst aquifer); CW is cost of surface water supply (RMB ¥/m3); EFil is where CDNi is the cost for controlling dissolved nitrogen loss from agricultural activity i (RMB ¥/kg); NeRAil is the amount of dissolved nitrogen loss from agricultural activity i in season l (kg/km2). The cost for management of solid-sate phosphorous loss is estimated by: