Some key points to remember

• Seepage: Water loss by downward and lateral movement of water.
• Readily available water (RAM) : 75% of available water and measured by following:

a) Neutron moisture meter b) Electrical resistance c) Tensiometer

• Moisture equivalent

1. MC = FC for medium textured soil
2. MC < FC for coarse textured soil
3. MC> FC for fine textured soil

• Consumptive use (CU) = T + E + metabolic process
• Evapotranspiration is measured by

a) Penmann method

b) Blaney-criddle method

c) Christiansen method

d) Thornthwoite method

• I_F > I_P , where, I_F = frequency of irrigation and I_p = Irrigation period
• Delta : total depth of water required by crop during its entire period of crop in field

  i.e. Delta ( Δ) = 8.64B/D

where, B = base period and measured in days

D = depth , ha/Cu mec

Δ = Delta, cm

• Shallow tube well ( STW) ; depth < 6m
• Deep tube well (DTW) ; depth > 6-45 m
• Aquifer: that region of soil from where water can be extracted.
• Base period: Time in days between 1^st irrigation at the time of sowing to its last irrigation before harvesting.