Hydrologic and economic evaluation of water-saving options in irrigation systems

• Published in: Irrigation and drainage 2008-02, Vol.57 (1), p.1-14
• Main Authors: Khan, S, Abbas, A, Gabriel, H.F, Rana, T, Robinson, D
• Format: Article
• Language: English
• Subjects: channel losses; cost analysis; costs and returns; economic evaluation; efficience de l'irrigation; irrigated farming; irrigation methods; irrigation systems; irrigation water; irrigation water costs; laser leveling; microirrigation; méthodes d'irrigation; on-farm and off-farm water losses; pertes en ligne (canaux); pertes à la parcelle et hors exploitation; subsurface irrigation; water conservation; water saving; water use efficiency; économie d'eau; évaluation économique
• ISSN: 1531-0353; 1531-0361
• DOI: 10.1002/ird.336

This paper investigates a range of water savings options at irrigation system level and ranks these options according to the potential savings of each option and the economic return in terms of water saved (ML - megalitres) for each dollar invested. Most of the work was conducted on large-area farms of the Murrumbidgee Irrigation Area (MIA) and Coleambally Irrigation Area (CIA) in the Murrumbidgee River catchment, New South Wales, Australia. Field-based on-farm water savings for scenarios analysed ranged from 0.1 ML ha⁻¹ up to 3.9 ML ha⁻¹ (10-390 mm). As capital can be a limiting resource to farmers, options that have the lowest cost per ML saved may be more appealing than options that have a higher cost but may also have higher net benefits over time. The water savings that derived the highest net benefit per megalitre saved were conversion to drip and subsurface drip for the case study farms and laser levelling which had net benefits ranging from A$ 1 64 to A$ 344 ML⁻¹ saved per year. All of the other options had net benefits ranging from A$ 4 to A$ 37 ML⁻¹ saved per year. All of the options that had a low annualised cost also had a relatively low net benefit (less than A$ 24 ML⁻¹ saved per year). Marginal costs of off-farm water savings increase with the volume of water saved. In the MIA up to 20 GL (1 gigalitre = 1 MCM million cubic metres) of potential water savings are possible at a marginal capital cost of around A$ 1500-2000 ML⁻¹. Marginal capital costs then rise rapidly, reaching A$ 4000 ML⁻¹ at around 38 GL reflecting the lower volumes saved at higher costs. Copyright © 2007 John Wiley & Sons, Ltd. 1A$ = Australian dollar. 1 A$ = 0.81 US$ (2007).