ISLAMABAD: An independent study of irrigation performance monitoring beyond water releases at outlet level has emphasised the need for improving irrigation management and inequity within the Lower Bari Doab Canal (LBDC) and possibly across the Indus Basin Irrigation System.

The study released by the Asian Development Bank and titled Optimisation of canal management using satellite measurements recommended that consideration must be given to operate the canals as close as possible to the design in both Kharif and Rabi seasons during high crop demand and save during less demand.

Gini co-efficient of water delivered in 2017 and 2018 showed that water delivery to gross command of distributaries in Kharif was more equitable than water delivered in Rabi and one of its possible reasons was that flow in Rabi season was well below the design, it says.

The Gini coefficient, named after its developer Italian statistician Corrado Gini, measures inequality among values of a frequency distribution, for example among levels of income.

The inequity in delivery may be minimised by reallocating water between divisions and the inequity within a division can be minimised by modifying rotation plan of the division.

Rabi and Kharif cover about 180 days and the 15 irrigation performance indicators posed were computed for every irrigation cycle and every distributary.

Modification of the rotational plan to maintain water surface level as close as possible to the design may improve equity. Better estimates of indents and revision of rotation plans based on historical performance may improve canal water supply equity across the distributaries, says the study.

A remote sensing-based decision support system (DSS) was developed for an irrigation system covering 756,000 hectares in Punjab. The DSS provides insight into irrigation requirements based on actual evapotranspiration and soil moisture contents. Results showed that delivered canal water varied among divisions, secondary canals called distributaries, and crop seasons, implying the system’s potential for water distribution improvements.

Two significant modifications have been suggested following the successful testing of the remote sensing approach. First is to revise division rotation plans based on the analysis of water delivered using data available in the real-time flow monitoring system (RTFMS) and water resources management information management system databases.

The second is to improve the setting of indents during irrigation season, using satellite-derived crop water demand, consumptive use, and soil moisture status. In the light of the implementation of the Water Act 2019 to perform integrated water resources management, the ADB study gives a great opportunity to the Punjab irrigation department for closely monitoring consumptive water use by agriculture and soil moisture in the root zone.

The study says that use of scarce water resources for improved equity and productivity can be regulated better. It might be applicable to comparable warabandi (water rotation) and protective irrigation systems, according to the study.

The study presents water deficit assessment of four divisions, and implies that Khanewal and Sahiwal are having higher consumptive water use and less water stress than Balloki and Okara, possibly because of the groundwater’s intensive use.

Published in Dawn, January 29th, 2021