Hydraulic and Operational Performance of Irrigation Schemes in View of Water Saving and Sustainability : Sugar Estates and Community Managed Schemes in Ethiopia

This book is about irrigation performance in two distinct typologies of irrigation schemes: large-scale sugar estate schemes and community managed schemes. The thesis identifies the major irrigation performance challenges and concerns in the two categories of schemes. Moreover, variations in performance between the same irrigation typologies as a result of differences in water management modalities were addressed. Hydraulic/water delivery performance in the sugar estate schemes was evaluated using routinely collected offtake flow data and hydrodynamic modelling. In addition to comparative performance evaluation, the thesis introduced assessing the internal irrigation service (utility) using qualitative data from the water users’ perspective in the community-managed schemes.

The rate of global increase in water abstraction for irrigation has been declining since the 1970’s due to declining potentials for large and medium-scale irrigation developments, and is expected to further decline in the next decades. As such the significant proportion of the expected increase in production would have to be supplied from existing irrigated and /or cultivated lands. This in turn could be achieved by enhancing land and water productivity through improved performance and optimal operation and maintenance.

With less than 15% of over 5 million ha irrigation potential harnessed, irrigation devolvement in Ethiopia remained low. Over 70% of the developed irrigation in the country belongs to small-scale irrigation serving smallholder farmers. While accelerated development of new irrigation, particularly of large and medium-scale schemes is relevant in Ethiopia, ensuring the performance and sustainability of existing schemes is also equally important. The existing irrigation schemes in Ethiopia are generally characterized by an overall performance and technical sustainability levels of below expectation.

This thesis evaluates the performance of two large-scale (Wonji-Shoa and Metahara) and two community-managed (Golgota and Wedecha) irrigation schemes located in the Awash River Basin of Ethiopia. The study focussed on hydraulic/water delivery performance in the large-scale schemes, and on comparative and internal irrigation service (utility) evaluation in the community-managed schemes. Water delivery performance was evaluated using routine data and hydrodynamic modelling. Farmers’ utility was evaluated using qualitative responses of water users. Major performance challenges in each category of schemes were addressed and operational/water management options for improvement were identified.