Their goal was to understand how regulatory agencies could allocate water to promote its equitable distribution. More recently, Winter (1995) provided a review of recent literature addressing the optimal and conjunctive allocation of ground – and surface –water resources.
2.4 Conjunctive Use and Irrigation Development
With regard to irrigation water, the implementation of sound conjunctive use projects involves a thorough inventory of soil and water resources and proper zoning of areas suitable for irrigation by surface or groundwater, or where one source can supplement the other. All this requires field surveys and investigations aiming at evaluating hydrometeorological, hydrological and hydrogeological conditions, seepage and soil infiltration rates, crop water requirements and crop patterns, water quality, hydrodynamic parameters and behavior of aquifers, well yields, canal flows and stream discharges, along with the assessment of energy costs to sustain both surface and groundwater development projects.
The beneficial effects of conjunctive use in canal commands can be summarized as follows (Karanth, 1987):
use of groundwater helps cope with peak demands for irrigation and hence reduce size of canals and consequently construction costs;
supplemental supplies from groundwater bodies ensure proper irrigation scheduling, even if rainfall fails or is delayed;
groundwater withdrawals lower the water table thus reducing the risk of water-logging, soil salinization and consequent wastage of water for leaching the soils;