Question

uncertainty of rainfall leads to demand of irrigation(give reason)​

Answer 1

rainfall is important for agricultural crops to grow faster and maintain the moisture in soil

due to uncertainty of rainfall agricultural crops cannot be grown because it requires water throughout their entire lifecycle to survive.

so irrigation is demanded because to meet water requirement of crops , helps to grow agricultural crops , maintain moisture for germination of seeds and makes the soil soft so that ploughing the land will be easier.