Sustainable water management in smallholder irrigation schemes: Understanding the impact of field water management on maize productivity on two irrigation schemes in Zimbabwe

Smallholder irrigation globally can be recognised as a crucial common property resource for the sustenance of rural livelihoods in semi-arid regions. This is particularly true for Zimbabwe where 70% of the population is situated in rural areas characterised by low and unpredictable rainfall patterns. This paper looks at the performance of smallholder irrigation schemes based on a technical evaluation of field water management and crop performance. Field water management was assessed by looking at the application efficiency (E-a), tail water ratio (TWR), deep percolation ratio (DPR), requirement efficiency (E-r) and distribution uniformity (DU). Crop performance and productivity was evaluated by looking at weekly crop heights and the overall crop yield. The study was conducted on two irrigation schemes in Zimbabwe's dry region V in Manicaland province. The two schemes (Chakohwa and Gudyanga irrigation schemes) are surface schemes using the border irrigation gmethod. E-a of less than 30% was common at Chakohwa whilst that at Gudyanga ranged above 50% with the remainder being lost as deep percolation in most cases. The irrigation borders were dyked at the end resulting in ponding and excess water application at the ends. Generally farmers at Chakohwa irrigation scheme have an unpredictable irrigation rotation thus influencing them to hoard water (E-r = 100%) whenever their turn came. The high rotation frequency (7 days), low infiltration rates and short borders (80m) at Gudyanga irrigation scheme saw the farmers under applying in some cases (E-r < 100%). Over application was only done by those farmers with a poor suction head and poorly levelled borders. There were no significant differences between the yields obtained across the schemes though within Chakohwa, yields were generally high for farmers near the water source compared to those at the tail end. (C) 2004 Published by Elsevier Ltd.