IRRIG8: Solid set irrigation

Permanent solid set systems (fixed sprinklers on risers, square/rectangular or triangular layout). Long-lateral (bike-shift) systems are not covered.

With the station operating: at the first test point or sprinkler downstream of the off-take, at a sprinkler in the middle and at the last sprinkler. Include the highest and lowest parts of the field. Use a pitot gauge at a sprinkler. With regulators, read upstream of them; sprinkler pressure is then taken as the lower of that reading and the regulator setting.

Twelve sprinklers of the same specification chosen across the irrigated area, avoiding the inlet ends of laterals. Shroud each with a loose hose and collect for at least 30 seconds or 20 litres. Eight or more give the measured flow uniformity (QDUlq) used in the field DU. Optionally repeat with the pressure changed by about 20% to find the discharge exponent and coefficient, then reset the system.

A collector identical to the test collectors, with a known volume of water, placed upwind of the test area. Each wet collector is corrected by the evaporation rate × the time from when the system was shut off to when its row was read.

A grid of collectors inside the rectangle between six adjacent sprinklers (three on each of two laterals) in a representative part of the station, with the whole station running. Columns run along the laterals and rows run across them: default 5 columns × 12 rows, the first a half spacing in from the sprinklers. For a triangular layout use the same grid; the four sprinklers on the offset lateral must run.

Shut the system off before reading collectors and record when each row was read.