Проектирование ирригационных и дренажных систем

Conjunctive Water Management in the Fixed Rotational Canal System: A Case Study from Punjab Pakistan

Abstract

Asad Sarwar Qureshi

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.