Aflaj irrigation and on-farm water management in northern Oman

Abstract

This paper reports on results from a case study on water management within a traditional, falaj irrigation system in northern Oman. In the planning and design of regional irrigation development programs, generalized assumptions are frequently made as to the efficiency of traditional surface irrigation systems. Although qualitative accounts abound, very little quantitative research has been conducted on on-farm water management within falaj systems. Daily irrigation applications and crop water use was monitored during an 11-month period among 6 farm holdings at Falaj Hageer in Wilayat Al-Awabi. Contrary to the frequent assumptions that all surface irrigation systems incur unnecessarily high water losses, on-farm ratios of crop water demand to irrigation supply were found to be relatively high. Based on actual crop water use, irrigation demand/supply ratios among monitored farms varied from 0.60 to 0.98, with a mean of 0.79. Examination of the soil moisture budget indicates that during most irrigations of wheat (cultivated in the low evapotranspiration months of October–March) sufficient water is applied for the shallow root zone to attain field capacity. With the exception of temporary periods of high falaj delivery flows or periods of rainfall, field capacity is usually not attained during irrigations within the more extensive root zones of date palm farms. The data presented in this paper should provide a better understanding of water use performance by farmers within traditional falaj systems. Moreover, these data should also serve to facilitate more effective development planning for irrigation water conservation programs in the region.