Irrigation mosaics: How are they different?

Z. Paydar, F.J. Cook, E. Xevi, Keith Bristow

Research output: Book chapter/Published conference paperConference paper

2 Citations (Scopus)

Abstract

Irrigation mosaics, involving discrete patches of irrigated land dispersed across the landscape, may offer an alternative to traditional large-scale contiguous irrigation systems. This might be particularly attractive as a means of delivering improved social and economic opportunities for rural and remote communities in northern Australia. However, the longer-term environmental impacts of irrigation mosaics that may impair the sustainability of an irrigation project and the surrounding area are still largely unknown.Existing knowledge on irrigation mosaics and implications within the context of sustainable development is very limited. However, there are some findings from studies of other systems, with spatial patterns in the landscape, which can be used to help with analysis of irrigation mosaics.From ecological research it appears that patch size,shape and spatial arrangement are important characteristics in landscape analysis. Some simple indices exist to describe attributes such as area,perimeter and patch shape. For conservation planning, the bigger the reserves are, the closer they are to each other, the more circular they are and linked by habitat corridors, the better they serve the purpose of nature conservation.Irrigation mosaics could be used to create or enhance ecotones in the landscape for greater biodiversity, improving the microclimate,minimising erosion, and in absorption of surplus material (nutrients, sediments, solutes) flowing from the surrounding fields, thus decreasing the discharge of the irrigation waste out of the irrigation area, a possible environmental off-site effect. On the other hand, fragmentation, which involves discontinuity of patches, can increase the vulnerability of patches to external disturbance,for example wind storm or drought.In a study of disposal basins in irrigated areas of the Riverine Plains in the Murray Darling Basin the leakage rate under the larger basins was observed to be less than the smaller basins. The observed relationship is bas the perimeter/area ratio of disposal basins and suggests that, analogous to irrigation mosaics, the leakage(recharge to groundwater) would be more from many separate patches than from one big contiguous irrigation area.The size of the irrigation patches has some implications in terms of operation, maintenance and environmental impacts of irrigation. In large irrigation schemes, lower unit costs result in cost effective provision of infrastructure as well as encouraging more government support. On the other hand, smaller schemes give greater opportunity to farmers to participate in planning and management of the system; they are better adapted to supplying local markets, and they incur smaller risk of adverse social impacts, such as displacement of settlements or disruption of wildlife habitats.This paper provides an overview of some biophysical aspects that can be used for further study of irrigation mosaics and their potential environmental impacts. Application of simple analytical solutions for particular groundwater condition indicates some of these impacts compared to the traditional large scale systems.It appears that irrigation mosaics could have both negative (more lateral recharge, salinisation,increased operational losses) and positive (filtering nutrient surplus, enhanced biodiversity, preventing erosion, reduced area of impact around the irrigation area, lower rate of watertable rise)effects on the environment.
Original languageEnglish
Title of host publicationLand, Water and Environmental Management
Subtitle of host publicationIntegrated Systems for Sustainability
EditorsL. Oxley, D. Kulasiri
Place of PublicationChristchurch, New Zealand
PublisherModelling and Simulation Society of Australia and New Zealand
Pages470-476
Number of pages7
ISBN (Electronic)9780975840030
Publication statusPublished - 2007
EventInternational Congress on Modelling and Simulation (MODSIM) - Christchurch, New Zealand
Duration: 10 Dec 200713 Dec 2007

Conference

ConferenceInternational Congress on Modelling and Simulation (MODSIM)
CountryNew Zealand
CityChristchurch
Period10/12/0713/12/07

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