The publications in this series record the work and thinking of IWMI researchers, and knowledge that the Institute's scientific management feels is worthy of documenting. This series will ensure that scientific data and other information gathered or prepared as a part of the research work of the Institute are recorded and referenced. Working Papers could include project reports, case studies, conference or workshop proceedings, discussion papers or reports on progress of research, country-specific research reports, monographs, etc. Working Papers may be copublished, by IWMI and partner organizations. Although most of the reports are published by IWMI staff and their collaborators, we welcome contributions from others. Each report is reviewed internally by IWMI staff. The reports are published and distributed both in hard copy and electronically (www.iwmi.org) and where possible all data and analyses will be available as separate downloadable files. Reports may be copied freely and cited with due acknowledgment. About IWMIThe International Water Management Institute (IWMI) is an international, research-for-development organization that works with governments, civil society and the private sector to solve water problems in developing countries and scale up solutions. Through partnership, IWMI combines research on the sustainable use of water and land resources, knowledge services and products with capacity strengthening, dialogue and policy analysis to support implementation of water management solutions for agriculture, ecosystems, climate change and inclusive economic growth. Headquartered in Colombo, Sri Lanka, IWMI is a CGIAR Research Center with offices in 13 countries and a global network of scientists operating in more than 30 countries.

Background The applicability of rainwater harvesting structure is very poor while the intended purpose is achievable in the Blue Nile basin. Therefore, this research was initiated to evaluate the performance of a rainwater harvesting structure and put possible strategies for dry season challenges. The study carried out for three years in the North West Ethiopia. Methods The data were analyzed using daily water balance model and other performance indicators (number of water day, relative irrigation supply, runoff storage efficiency and marginal rate of return). Results At the inception, it was established that the existing rain water harvesting system performs very low, runoff storage efficiency below 46%, no zero water day above 50%, relative irrigation supply below 27 % and marginal rate of return from 12 to 65%. However the greater the volume of the rain water harvesting structure the higher runoff storage efficiency, higher relative irrigation supply, and lower no water day under different irrigation technique was achieved. Conclusions For attaining household irrigation water demand in the dry season, the user should adopt storage capacity of 630m3 in Nitisol and 361m3 in Vertisol for double cropping and 273 m3 in Rigosol for supplemental irrigation. Hence, applying rainwater harvesting technologies with efficient water management technique enhance the net benefit of the system.

Proper scheduling gave water to the crop at the right time in the right quantity to optimize production and minimize adverse environmental impact. Therefore, the objective of this study is to quantify the effects of irrigation regimes on yield and yield components of Maize in the Lake Tana basin during 2016-2018. CROPWAT 8.0 model was used to determine the crop water requirement. Almost all parameters were adopted the default value of CROPWAT 8.0. Field data including; field capacity (FC), permanent wilting point (PWP), initial soil moisture depletion (%), available water holding capacity (mm/meter), infiltration rates (mm/day), and local climate data were determined in the study area. The treatments were arranged in factorial combinations with five irrigation depths (50, 75, 100, 125 and 150% of ETc) and two irrigation intervals (14 and 21 days) laid out in a randomized complete block design with three replications. The result was analyzed using SAS 9 software and significant treatment means separated using least significant difference at 5%. The result showed that the interaction of irrigation depth and irrigation frequency has no significant effect on the average grain yield and water use efficiency of maize. At koga, the highest grain yield (7.3 t ha-1) and water use efficiency (0.9 kg m-3) obtained from 100% ETc. while, at Ribb the highest grain yield (10.97 t ha-1) and water use efficiency (1.9 kg m-3) obtained from 21 days irrigation interval. Therefore, for Koga and similar agro ecologies maize can irrigated with 562 mm net irrigation depth and 21-day irrigation interval and at Rib and similar agro ecologies maize can irrigated with 446.8 mm net irrigation depth and 21- days irrigation interval.

Background Proper scheduling gave water to the crop at the right time in the right quantity to optimize production and minimize adverse environmental impact. Therefore, the objective of this study is to quantify the effects of irrigation regimes on yield and yield components of Maize in the Lake Tana basin during 2016–2018. Methods CROPWAT 8.0 model was used to determine the crop water requirement. Almost all parameters were adopted the default value of CROPWAT 8.0. Field data including; field capacity (FC), permanent wilting point (PWP), initial soil moisture depletion (%), available water holding capacity (mm/meter), infiltration rates (mm/day), and local climate data were determined in the study area. The treatments were arranged in factorial combinations with five irrigation depths (50, 75, 100, 125 and 150% of ETc) and two irrigation intervals (14 and 21 days) laid out in a randomized complete block design with three replications. Results The result was analyzed using SAS 9 software and significant treatment means separated using least significant difference at 5%. The result showed that the interaction of irrigation depth and irrigation frequency has no significant effect on the average grain yield and water use efficiency of maize. At koga, the highest grain yield (7.3 t ha− 1) and water use efficiency (0.9 kg m-3) obtained from 100% ETc. while, at Ribb the highest grain yield (10.97 t ha− 1) and water use efficiency (1.9 kg m− 3) obtained from 21 days irrigation interval. Conclusion Therefore, for Koga and similar agro ecologies maize can irrigated with 562 mm net irrigation depth and 21-day irrigation interval and at Rib and similar agro ecologies maize can irrigated with 446.8 mm net irrigation depth and 21- days irrigation interval.