CONJUNCTIVE USE OF WATER: OBJECTIVE ADVANTAGE AND CONSTRAINTS
CONJUNCTIVE USE OF WATER
Definition
The term “Conjunctive use “of water resource implies the coordinated and harmonious development for increased
efficiency of water from different resources. Thus Conjunctive use of water resource can be defined as “ the management of multiple water resources in a coordinated operation such that, the water yield of the system over a period of time exceeds, the sum
of yields of the individual components of the system, resulting from in coordinated operation”. It is not mutely providing groundwater supply and
distribution system as a back up for a surface water system or vice versa, rather it is a concept in which one system complements and supplements the other to compensate for the inadequacies of both “.It is integrated management of both surface and ground water components in order to make best use of the complement ary potential of each and to optimize the use of water resources.
Objectives
1. Mitigating the effect of shortages in canal water supply
2. Increasing the dependability of existing water supply
3. Alleviating the problem of high water table and salinity
4. Facilitating the use of high salinity ground water.
5. Mitigating the damages due to drought.
6. Increasing the efficiency of
surface water system.
Systems of conjunctive use
Abrol et al. (1988) listed the following systems of conjunctive
use:
1. Canal water and ground water system
2. Rainfall and irrigation water system
3. Saline water and fresh water system.
Advantages
1. Use of ground water helps reduce peak demands for irrigation, size of canals, and hence construction costs
2. Supplemental supplies from groundwater ensure proper irrigation scheduling raising multiple crops and early sowing even if rainfall is delayed
3. Increased water resources ensure supply to tail end areas of higher elevation.
4. Ground water exploitation lowers the water table and reduces danger of water logging and consequent wastage of water for leaching of soils
5. Surface and subsurface out flows are minimized causing reduction in peak run off and flood discharge
6. Conjunctive use when integrated with an artificial recharge project the need for lining of canals is reduced as seepage from canals recharges ground water
7. During periods of peak water demand irrigation requirement can be met by surface water sources, so power saved can be diverted to other sectors
8. Conjunctive use is an attractive benefit considering the difficult political and environmental challenges facing many surface water storage projects
Constraints
1. Possibility of deterioration in ground-water quality due to influx of salts leached down from the soil which may be quite marked as a result of recycling within cones of depressions and / or upward and lateral migration of saline water intro fresh water zones in response to pumping.
2. Increased power consumption to sustain pump age from wells. Possible dislocation of groundwater supplies due to power failure in critical periods, and decrease in pump efficiencies supplies due large fluctuations in water levels.
3. Operation, supervision and control of conjunctive use and
artificial recharge projects are more complex.
4.Administrative difficulties in evolving acceptable and equitable water rates, providing motivation and incentives to accept groundwater use when surface water is available(Aquifer storage and Recovery (ASR) is a form of conjunctive use where excess water is stored under
ground is a suitable aquifer later as needed).
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