How do I build and use a PVC field water tube for AWD in paddy?

For alternate wetting and drying (AWD) take a PVC or bamboo pipe about 25 to 30 cm long and 10 to 15 cm wide, drill many small holes in the lower 15 cm, push it into the soil so the holed part is below ground and a few cm sticks above, and scoop out the soil inside so you can see the water level. After the crop is established for 2 to 3 weeks, let the water in the tube fall to about 15 cm below the soil surface, then re-irrigate, except keep a thin water film during flowering. This safe AWD can cut water use by 15 to 30 percent with little yield loss and reduces pumping cost. Place the tube in an average, not the lowest, part of the field. Avoid AWD on very leaky sandy soils.