Question

what is mean of river valley system of irrigation

Answer 1

Explanation:  

The river valley is a valley formed by a river.

The river valley system of irrigation means artificial canals, ditches, etc. Its use is to promote the growth of food crops. It means fetching water from the river and irrigating the field from that water. This is what is meant by the system of irrigation.  

We give water to the plants by this process. This is the easiest process of giving water to the field.