The irrigation system in Kobo-Girrana valley is extensively developed into modern drip irrigation using ground water sources. Tomato and onion are among the major vegetables grown under drip irrigation. However, the drip lateral spacing is fixed to 1m for all irrigated crops. This leads to low crop water productivity, loss of land, less net return income and un-optimized irrigation production.

An on-station experiment was conducted to determine the effect of drip line spacing and irrigation regime on yield, irrigation water use efficiency and net return income. The experiment was carried out for two consecutive irrigation seasons in 2010/11 and 2011/12 at Kobo irrigation research station. The experimental treatments were: two lateral spacing of single row and double row corresponding to each test crop and three irrigation regime (Kp = 0.8, 1.0 and 1.2).

The results revealed that an interaction effect between the lateral spacing and irrigation regime was obtained in marketable yield and water productivity of test crops. Application of 0.8 Kp with 2m lateral spacing and 1.2 Kp with 1m lateral spacing provided relatively higher marketable yield of tomato and onion, respectively. Similarly, high water productivity was recorded with same irrigation depths and spacing regimes as to the yield.

This result generally revealed that one lateral design for each two plant rows gave high net income than the one lateral design for each one plant row for drip irrigated fresh marketable yield of onion and tomato. An optimized production and irrigation efficiency can be attained by applying irrigation depth adjusted by the given pan coefficients and drip lateral spacing in Kobo areas.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

This paper examines the advance time of furrow irrigation at Koga.

Koga irrigation scheme was developed to irrigate about 7004 ha. Furrow irrigation is the recommended method for the distribution of water. However, furrow irrigation has inherent inefficiencies due to deep percolation on the upper end and runoff at the lower end of the furrow. These losses depend on furrow length, furrow gradient, surface roughness, stream size and cutoff time. These factors play significant role to influence the advance time of irrigation and the operation rule of the scheme.

The experiment was conducted during 2012 irrigation season in two periods (February and April). The advance time of irrigation was monitored at three discharge rates and four furrow gradients at 90–110 m furrow length. The required discharge was measured using RBC flume. The average advance time at respective discharge rates of 0.3, 0.6 and 0.8 litre/sec range from 290–460 min, 150–437 min and 100–294 min during 1st irrigation; and 115–370 min, 78–189 min and 43–217 min during 2nd irrigation. The advance time vary greatly among the discharge rates when the furrow length increases. The advance time of water at 0.5, 1.0, 2.0 and 2.5 % gradients was 236, 181, 197 and 398 min at 1st irrigation and 163, 175, 220 and 88 min at 2nd irrigation respectively. Furrow gradients and surface irregularities result in great variation of advance time. The advance time becomes shorter when the field gets smoother during 2nd irrigation. Under non-levelled and irregular field conditions, 0.6–0.8 litre/sec application rate can be suggested to irrigate 30–40 m furrow lengths in order to improve application efficiency above 60% and to optimize the daily operation rule of the overall scheme.

The result of this study indicates the relevance of examining the furrow length, discharge and application time recommended in the feasibility study of irrigation schemes.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

This study uses Tobit and Logit models to examine the impacts of selected small-scale irrigation schemes in the Lake Tana basin of Ethiopia on household income and the likelihood of poverty, respectively.

Data for these analyses were collected from a sample of 180 households. Households using any of the four irrigation systems had statistically significantly higher mean total gross household income than households not using irrigation. The marginal impact of small-scale irrigation on gross household income indicated that each small scale-irrigation user increased mean annual household income by ETB 3353 per year, a 27% increase over income for non-irrigating households.

A Logit regression model indicated that access to irrigation significantly reduced the odds that a household would be in the lowest quartile of household income, the poverty threshold used in this study. Households using concrete canal river diversion had higher mean cropping income per household than those using other irrigation types.

Key challenges to further enhancing the benefits of irrigation in the region include water seepage, equity of water distribution, availability of irrigation equipment, marketing of irrigated crops and crop diseases facilitated by irrigation practices.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

Although Ethiopia has a large potential to develop irrigation, only 5% of the 3.5 million hectares of land potentially available has been developed. To examine the underlying causes, this study evaluates the suitability of surface water irrigation for the Lake Tana Basin development corridor.

Surface water availability and land potentially suitable for medium and large-scale irrigation development (200 ha and larger) was considered. Surface water potential was examined by considering river discharges. Land suitable for irrigation was determined with a GIS-based multi-criteria evaluation (MCE), which considers the interaction of various factors, such as climate, river proximity, soil type, land cover, topography/slope and market outlets.

The result indicates that nearly 11% of the Lake Tana Basin is suitable for surface irrigation. However, by analysing 27 years of river discharge, less than 3% of the potential irrigable area (or less than 0.25% of the basin area) could be irrigated consistently by run-of-the river-systems. Thus, the irrigation potential in the Lake Tana Basin can only be met by increasing dry season flows (if proven feasible) and by supplying water from existing or future reservoirs or by using water directly from Lake Tana.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.

This paper calls attention to the importance of social cooperation in irrigation farming. It argues that a mere focus on the technical aspect of irrigation, disregarding its social aspects undermines the long-term benefits of irrigation to rural livelihoods.

This assertion draws on lessons from small-irrigation practices in Fogera, in the Blue Nile Basin of Ethiopia, where the research conducted fieldwork-based qualitative research. In recent years irrigation farming has drawn a growing interest among farmers in rural Fogera. Farmers practise small-scale irrigation that includes traditional irrigation and motor pump irrigation. Farmers assert that irrigation has brought farming benefits through cultivation of more crops as well as new crops that serve food and cash purposes. Such benefits have particularly spurred the enthusiasm for motor pump irrigation.

However, the practice of motor pump irrigation largely relies on the motor-pump technology, overlooking the social scheme of irrigation. While traditional irrigation involves more social cooperation involving joint activities, water allocations and irrigation schedules, lack of social cooperation and such institutional conditions is widespread in motor pump irrigation. Local classification of irrigation practices also associate the mechanism of irrigation use and management including water use regulations and water use turns with traditional irrigation in contrast to motor pump irrigation.

The neglect of social cooperation within current practices of motor pump irrigation will have significant adverse implications on long-term practices. Farmers have been already concerned about how competitions for water are growing, limiting the duration of water availability and creating water shortage.

The study suggests that while farmers’ willingness to practise motor pump irrigation in Fogera has been stimulated by its livelihood benefits, sustained benefits of this irrigation scheme require social cooperation and feasible institutional conditions that can mediate water usage across user villages.

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This paper was first presented at the Nile Basin Development Challenge Science meeting. The NBDC Science meeting was held on 9 and 10 July 2013 at the ILRI-Ethiopia campus, with the objectives to exchange experiences and research results across NBDC scientists involved in the NBDC projects and to discuss challenges and possible solutions.