Total water requirement (consumptive use + application losses) of field crops:
Rice (Paddy): 1200 - 1500 mm (or up to 2000 mm including puddling and continuous submergence losses; highest among seasonal cereals).
Maize: 500 - 800 mm.
Wheat: 450 - 650 mm.

Crop coefficient (\(K_c\)) dynamics during crop growth (FAO-56 guidelines):
The crop coefficient curve represents the ratio of crop evapotranspiration to reference evapotranspiration (\(K_c = ET_c / ET_0\)).
For watermelon:

• Initial stage (\(K_{c,\text{ini}}\))\lt /strong\gt : \(0.40 - 0.45\) (ground cover is $\lt 10\%$).
• Crop development stage: \(K_c\) rises steeply as vegetative foliage expands.
• Mid-season stage (\(K_{c,\text{mid}}\))\lt /strong\gt : Reaches peak value of \lt strong\gt \(1.00\text{ to }1.05\) when complete ground cover, flowering, and active fruit enlargement occur.
• Late-season stage (\(K_{c,\text{end}}\))\lt /strong\gt : Declines to \(0.75 - 0.80\) as leaves senesce and fruits mature. Therefore, the maximum \(K_c\) value occurs during the mid-season stage.