Final answer:
To answer the student's question, the water stored for ETc in a border strip irrigation system that operates 2 days after the perfect timing day can be calculated by considering the water applied, distribution uniformity, and ETc depletion over the two days delay for both the adequately irrigated and under-irrigated areas.
Step-by-step explanation:
The student's question revolves around calculating the amount of water stored for Evapotranspiration (ETc) when irrigation occurs two days after the ideal irrigation timing. Given a border strip irrigation system, designed to deliver 3.5 inches of water with a Distribution Uniformity (DU) of 0.64, and an ETc of 0.20 inches per day. Since there is a 25% under-irrigated area, the effective amount of water available to the crop will be the water applied (3.5 inches) multiplied by the DU (0.64), and considering the delay in irrigation, the available water for ETc on the day of irrigation will be the water stored minus the ETc for two days for the 75% adequately irrigated area.
To calculate the total amount of water stored for ETc, we should consider both the adequately irrigated and under-irrigated areas. For the adequately irrigated 75% of the area, the water applied would be 3.5 inches (irrigation depth) * 0.64 (DU) = 2.24 inches. Over two days, ETc would deplete 0.20 inches/day * 2 days = 0.40 inches. For the under-irrigated 25% of the area, since no PI losses and runoff are reported, we assume the ETc remains the same, and therefore, the stored water for ETc will be 0 inches for this portion. The combined stored ETc will be based on the sum of the water stored for both portions of the field.