Abstract
In the fixed rotational irrigation system of Pakistan, canal water supplies are usually deficient to meet crop water requirements. Therefore groundwater is widely used to supplement surface supplies. In most of the canal command areas, groundwater is used in conjunction with the surface water to decrease the salinity of irrigation water in an attempt to avoid soil salinization. However, conjunctive use of surface water and groundwater is equally practiced in head and tail ends of the canal system. This results in rising groundwater tables leading to waterlogging in the upstream areas and aggravating salinity problems in the tail areas due to less canal water availability and the poor quality of the groundwater. Therefore strategies need to be developed for surface and groundwater use in such a way that equity in availability of water of acceptable quality is ensured all along the channel. This paper suggests three options to achieve this objective; (1) development of guidelines for proper mixing ratios of surface water and groundwater to maintain acceptable salinity levels; (2) revisiting canal water allocations to provide more canal water to tail-end farmers due to poor quality of groundwater whereas encouraging head farmers to extract more groundwater to meet their demands; and (3) facilitating farmers to develop on-farm storage ponds to store their meager share of canal water and use it through high efficiency irrigation systems such as drip and sprinkler. All these options would require necessary changes in the government policies, institutional arrangements and wide scale dialogue with farmers. For this purpose, network of existing water user associations may play a vital role.
Highlights
Surface water and groundwater typically have a natural hydrologic connection
In Pakistani Punjab, conjunctive use of surface water and groundwater is practiced in head and tail ends of the canal system
The unregulated conjunctive use of groundwater and surface water is replete with serious consequences as it created waterlogging conditions in the head reaches and increase salinity of the soils in the tail reaches of the same canal system
Summary
Surface water and groundwater typically have a natural hydrologic connection. Conjunctive water use is an approach that recognizes this connection and facilitates the use of the overall water supply more efficiently. The optimal farm level production performance is achieved where farmers are able to use the less expensive surface water and supplement with groundwater to fill the shortfalls [4,5] Under these conditions, conjunctive water management becomes much more complex because of its important role in improving livelihoods of farmers and rural economies. This paper discusses conjunctive water use patterns and its consequences on cop production and soil salinization with a special reference to decreasing surface water availability and increasing groundwater salinity from head to tail end of a typical (Hakra) canal command system in the Punjab Pakistan. The surface water flow, cropping pattern, soil salinity conditions and groundwater use patterns of the Hakra branch canal reflects true picture of most of other canal command areas in the Punjab province. Rice and sugarcane are planted on about 10 percent of the area mainly in the head reaches of the canal
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