Consultants have been hired to do this job. They are generally known as Mobile Irrigation Laboratories. IES and nonpoint source pollution programs. To review, NPS generally occurs in a 3-step process. As related to irrigation, surface runoff can carry sediments, along with adsorbed chemicals and fertilizers to surface water bodies.
Deep percolation can carry soluble chemicals and fertilizers into ground water.
Surface runoff and deep percolation beyond leaching requirements. Please refer to the Advisory concerning Irrigation Performance Measurements . Note that in certain situations, maybe it will be best to look to timing, control, scheduling first. Calculation of IE also depends on accurate measurements of water volumes applied and drained from the field, and soil moisture depletions before and after the irrigation. Estimates of irrigation efficiency are open to misinterpretation.