International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



Conjunctive Water Use

Conjunctive water use is the coordinated management of surface water and groundwater supplies to maximize the yield of the overall water resource. A passive method is to simply rely on surface water in wet years and use groundwater in dry years. It can be managerial where both surface water and groundwater are withdrawn in a coordinated manner; physical where the two resources are hydraulically interconnected; and legal where the use of one conserves the other for another time. What is common is the conjunctive use of both resources to meet water supply needs.

 

Surface water is available seasonally, but usually with some degree of uncertainty as to time and amount available. However, it is possible to determine the size of surface storage facilities necessary to regulate supply for desired output characteristics, despite the irregular inflow from natural resources. Surface storage facilities are characterised by rapid fill up, evaporation, seepage losses, and high initial costs. On the other hand, groundwater is usually available in vast quantities in large aquifers, with little variation in time, hence causing less uncertainty in availability prediction than that of surface water.

 

The importance of conjunctive use lies in the interaction between the two characteristically different water sources. This interaction is part of the hydrologic cycle, such as natural replenishment, artificial recharge; return flow from irrigation and sewage, and stream-aquifer interaction. There are two main aspects of this interaction: the flow of groundwater to support river flow and the flow from the river to the groundwater. The former is a common occurrence in temperate regions, whereas the latter occurs widely in arid regions.

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Dictionary - Conjunctive Water Use Terms

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