Irrigation optimization with variable water quality and nonuniform soil.

ABSTRACT A furrow irrigation system is optimized considering irrigation water quality and nonuniformity of water infiltration characteristics. A volume balance hydraulic model including a runoff recovery system provides input to another model that calculates maximum profit as a function of flow rate and irrigation time. Infiltration function nonuniformity and poor quality of applied water reduce maximum profit. Optimal furrow flow rate decreases and irrigation time increases slightly as applied water becomes more expensive but the strategy reverses when the unit cost of drainage increases. Optimal flow rate is greater and irrigation time is less for a soil with a heterogeneous infiltration function compared to the same soil with the infiltration function spatially averaged. Volume of drainage decreases sharply with increases in unit cost for drainage water and is influenced little by water quality and irrigation water cost.