Irrigation: Basic Concepts

These terms are mainly used in canal irrigation engineering. When a new canal is constructed, the engineers create its design maps etc. While doing so, they chalk out the entire area within an imaginary line that can be included in the irrigation project under development. This Gross Command Area (GCA) includes cultivable land as well as barren land, forests, houses, wasteland, roads etc.

Cultivable Command Area is that part of Gross Command Area, which is fit for cultivating crops. So, cultivable area excludes forest and barren land from the Gross Command Area. What is left is uncultivable area.

Gross Command Area=Cultivable Command Area + Uncultivable Area

The key feature of cultural command area is that it can be physically irrigated from a scheme and is fit for cultivation of crops.

We can classify the irrigated area into gross and net irrigated area. The Net Irrigated Area is the actual land area on which irrigation was used for growing crops for as many times as many in an agricultural year {Agricultural Year is from 1^st July to 30^th June}. On the other hand, Gross irrigated area is the total irrigated area under various crops during the year counting the area irrigated under more than one crop during the same year as many times as the number of crops grown, crops sown mixed being taken as one crop. Thus, if a crop is grown for more than one time in an agricultural year, the Gross Irrigated Area will count the irrigated area for more than once. We note here that out of about 141 m. Ha of net area sown in the country, about 65 million hectare (or 45%) is presently covered under irrigation.

There is a huge difference between irrigation potential created and utilized. Irrigation potential created is the total area which can be irrigated from a project on its full utilization. This implies that before an area is to be reported under “potential created”, it is to be ensured that:

• Water is available for the area to be irrigated in each season during a complete irrigation year
• Conveyance system is available to carry water up to where it is needed
• The projected cropping pattern of the region is satisfactorily adhered to.

This implies that Irrigated Potential Created denotes full utilization. If the area actually irrigated is smaller than the potential created, it denotes under-utilization. Thus, irrigation utilization is percentage of actual irrigated area to potential created.

We note here that the Irrigation potential ‘created’ figures are generally inflated figures and they are declared without paying attention to construction of proper construction network.  Sometimes, even if water is available, it cannot be taken to the farm where it is actually needed; but potential created is shown in papers.

Thus, while the irrigated area created is merely a notional figure. The irrigation potential utilized is gross cultivable area actually irrigated during 1993-94 out of the gross proposed area to be irrigated by the scheme during the year.

A minor irrigation scheme has Cultural Command Area (CCA) up to 2000 Hectares. A medium Irrigation scheme has CCA from 2000 Hectares to 10000 Hectares. A major irrigation scheme has a CCA above 10,000 hectares.

Further, Micro-irrigation encompasses drip and sprinkler technologies which have helped in getting more crop per drop.