Read this article to learn about the most important advantages of conjunctive use of surface and ground water.
Timely supply of irrigation water in adequate quantities is essential for a good crop yields. It is all the more necessary in case of high yielding verities. Surface water schemes do not have sufficient flexibility and so, the roster of the operating channels cannot be adjusted to provide timely irrigation in the command area for various crops with different base and critical periods. The needs cannot also be economically met from groundwater alone on account of pumping efforts required for lifting the water. Thus, conjunctive use can help meet the requirements both in respect of quantity and time.
Continuous and excessive use of surface water in canal command areas without proper surface drainage and/or adequate groundwater development results in alarming rise of waters table, creating problem of water-logging and salinisation, affecting crop growth adversely and rendering large areas unproductive. With increasing intensities of irrigation and tendency on the part of the cultivators to over supply irrigation from surface-water, the problem gets aggravated further.
Simultaneous development of groundwater specially through dug-wells and shallow tube wells lowers water table, provides vertical drainage and thus can prevent water-logging and salinisation. Areas which are already water logged can also be reclaimed.
In case of coastal areas, the excessive pump-age of groundwater has been responsible for causing gradual movement of seawater into inland aquifers. This salt water intrusion makes fresh groundwater saline, rendering it unfit for many purposes. Such a condition can also occur in the inland areas due to lowering of water level as a result of excessive withdrawal of fresh water in the vicinity of a saline water zone. This situation can be controlled by increased application of surface waters by encouraging conjunctive use.
Continuous increased withdrawals from a groundwater reservoir in excess of replenish-able recharge has resulted in regular lowering of waters table leading to mining of the groundwater. In such a situation a serious problem is created resulting in drying of shallow wells and increase in pluming head for deeper wells and tube wells. The remedy lies in providing more surface water irrigation with the help of storage reservoirs, inter-basin transfer, etc. In some cases recourse will also have to be taken for providing artificial recharge to groundwater.
In certain areas the surface water is not able to meet full demand of irrigation water. At the same time, groundwater being saline, direct application is not possible. In such cases, conjunctive use can be made by construction of augmentation tube wells and mixing the saline water with canal water to the extent that the quality of mixed water remains within tolerable limits of corps.
In certain areas, ground water is available but there is no direct use in that area. In such cases, it can be transferred to other needy areas by construction of augmentation canals fed by battery of augmentation tube wells.
This has already been done in Haryana and Punjab. In U.P. it is proposed in Gandak and Sarda Sahayak Commands. In respect of augmentation tube wells (ATW), Haryana was the first State to install 160 ATWs for conjunctive use in the year 1972, in Western Yamuna canal tract to feed the 75 km long augmentation canal to the extent of 14 cumec during the lean season.
Leakage from unlined canals may be recovered in certain areas by pumping in preference to control of seepage through costly canal lining; this water may be pumped back into the canal or used directly for irrigation.