Runoff irrigation practices and challenges in western lowlands of Eritrea

Introduction. The arid and semi-desert lowland agro-ecological zones of Eritrea experience lowprecipitation, much lower than the requirements forrobust agricultural production unless supplemented by properly functioning runoff irrigation systems. However, an in-depth understandingof the principles and practices of runoff irrigation, identification of itspotentials and challengesand come up with viable solutions is necessary. Materials and methods. Qualitative and quantitative, descriptive and analytical research methodologies are applied. Primary and secondary data are used to identify existing constraints. Besides, global and regional databases are extensively utilized to fill information gaps. Results. The total potential cultivable land of Eritrea amounts to 2.1 million ha, out of which 71.4 % is rainfed and 28.6 % is irrigation. But, the potential irrigable land as reported by FAO is much lower (187,500 ha), out of which 50,000 ha is within the Western Lowlands. Considering such disparities and the less likely scenario of lowest irrigation potential, the actual equipped for spate irrigation at national level would amount to only 33.6 %, meaning there are still a lot of possibilities for expansion. The causes of malfunctioning of the existing systems are associated to structural, operation and maintenance, and management. Lack of historical hydrological data is among the highly likely reasons, which in turn greatly affects hydrological simulations. Conclusions. Despitecommendable efforts made to expand the improved runoff irrigation in the Western Lowlands, most of the projectshavefailed to achieve the intended purposes. Thus, comprehensive and simple mathematical modelsfor ma­king hydrological predictions have been suggested.

Impact of Minor Irrigation on Agricultural Production: An Inter-Crop Analysis in Odisha

The study examined the impact of minor irrigation on agricultural production and evaluated the gap between IPC and IPU in the Keonjhar district of Odisha. For this rationale, data were collected from 210 farm households through the primary survey. In support of the analysis, the Cobb Douglas model and factor analysis were used. The results revealed that the input use efficiency had a positive and significant impact on paddy production the most in all the MIPs regions compared to the other crops. However, the study indicated that insufficient water availability was the major cause behind the gap between irrigation potential created and utilised. Thus, minor irrigation played a crucial role in enhancing agricultural production in hilly regions. With the enthusiastic participation of planners, effective working of Pani Panchayats, canals, and upstream control, NGOs' involvement can achieve selfsufficiency in agricultural production by encouraging minor irrigation projects in the hilly province.

Estimating Surface and Groundwater Irrigation Potential under Different Conservation Agricultural Practices and Irrigation Systems in the Ethiopian Highlands

This study was conducted at the Dangishta watershed in the Ethiopian highlands to evaluate irrigation potential from surface and groundwater sources under different farming and water application systems. Daily streamflow and the groundwater table were monitored from 2015 to 2017. Shallow groundwater recharge was estimated using the water table fluctuation method. Automated baseflow separation techniques were used to determine the amount of runoff and baseflow from the total streamflow records. The potential of groundwater and runoff to sustain dry season irrigation (i.e., low flow) was evaluated considering two tillage systems (i.e., conservation agriculture, CA; and conventional tillage, CT), and water application (i.e., drip and overhead) systems for major irrigated crops (i.e., onion, garlic, cabbage, and pepper) grown in the Dangishta watershed. We found that the annual groundwater recharge varied from 320 to 358 mm during the study period, which was about 17% to 22% of the annual rainfall. The annual surface runoff depth ranged from 192 to 268 mm from 2015 to 2017. The results reveal that the maximum seasonal irrigable land from groundwater recharge was observed under CA with drip irrigation (i.e., 2251 and 2992 ha from groundwater recharge and surface runoff, respectively). By comparison, in the CT practice with overhead irrigation, the lowest seasonal irrigable land was observed (i.e., 1746 and 2121 ha from groundwater and surface runoff, respectively). From the low flow analysis, about 199 and 173 ha of one season’s irrigable land could be irrigated using the CA and CT systems, respectively, both with drip irrigation. Similarly, two-season overhead irrigation potential from low flow under CA and CT was found to be about 87 and 76 ha, respectively. The dry season irrigable land using low flow could be increased from 9% to 16% using the CA system for the various vegetables, whereas drip irrigation could increase the irrigable land potential by 56% compared to overhead irrigation. The combined use of groundwater recharge and runoff could sustain up to 94% of the dry season low flow irrigation through the combination of the CA system and drip irrigation. Decision makers must consider the introduction of feasible and affordable technologies to make use of groundwater and direct runoff, to maximize the potential of dry season production through efficient and appropriate CA and water management practices.

Scenarios of sustainable irrigation expansion in the 21st century

Irrigation expansion onto rainfed croplands is an important part of the portfolio of agricultural measures, contributing to a more resilient crop production while enhancing agricultural yields. Existing global assessments of irrigation illustrate the biophysical potential, but generally do not account for socioeconomic and environmental constraints to irrigation deployment. Here we provide scenarios of regionalized sustainable irrigation expansion linked to socioeconomic projections from the Shared Socioeconomic Pathways framework, while accounting for biophysical irrigation limits. Under a Sustainability scenario, we find that sustainable irrigation could feed 2 billion people globally by 2100. With an additional 90 million people, sub-Saharan Africa is the region with the highest percentage increase in people fed via sustainable irrigation deployment. However, even under the most optimistic scenarios only half of the theoretically possible global biophysical irrigation potential would be utilized after accounting for socioeconomic constraints. Our results highlight the need for appropriate representation of socioeconomic factors in scenarios of future irrigation deployment.

Climate change impacts on irrigation water resource in Switzerland

<p>According to climate projections, rainfall rates and summer discharge from snow and glacier melt in Switzerland are expected to decrease by the end of the 21<sup>st</sup> century. This may lead to limited water availability for irrigation in agriculture in the future and high irrigation water demand especially during the summer months, which consequently enhances the problem of water scarcity for agriculture.</p><p>These predicted changes make the identification of timescales, frequencies, and geographical pattern of water scarcity a fundamental concern for future agricultural practices. Therefore, the main aim of this work is to investigate climate change impacts on water resources and the consequences on irrigation water supply in Switzerland. By creating maps of the geographic distribution of natural water resources available according to climate projections until the end of the 21<sup>st</sup> century using ArcGIS, the severity of water scarcity is quantified, while regional differences and the most affected areas can be revealed.</p><p>The expected outcomes are increasing days of water scarcity per year over the course of the 21<sup>st</sup> century, while those regions furthest away from melt water sources and lakes will be most affected. This in turn might lead to restricted irrigation potential, making more efficient water use indispensable in Switzerland, while creating general shifts to more water-resistant crops in Swiss agricultural practices.</p>

A re-look at canal irrigation system performance: a pilot study of the Sina irrigation system in Maharashtra, India

The general perception of canal irrigation systems in India is one of built infrastructure with low service performance. This paper presents an analytical framework, applied to the Sina medium irrigation system in Maharashtra state of India, to study the performance of an expanded water influence zone (WIZ) including a buffer zone outside the canal command area (CCA) influenced by the irrigation system's water resources. The framework used satellite-based estimates of land-use and cropping patterns. The results indicate that there is hardly any gap between the irrigation potential created (IPC) and the irrigation potential utilized (IPU) in the CCA. The fraction of consumptive water use (CWU) of irrigation is low in the CCA, but almost one in the WIZ, due to the reuse of return flows in the WIZ. Future investments should focus on increasing economic water productivity ($/m3) in order to enhance the resilience of the farming community in the WIZ, which is frequently affected by water scarcity.

OPTIMUM ALLOCATION OF DIFFERENT SOURCES OF IRRIGATION

Discovery of agriculture was no doubt the greatest development in the history of mankind. Irrigation, being one of the most crucial input in the process of agricultural development, has been sought to be developed. In India, although significant efforts have been made to develop the irrigation potential through major and minor irrigation, yet there has been rather inadequate awareness of the economics of irrigation. Particularly, very few comparable attempts have been made to examine the rational allocation of water between different regions, crops and over time. Most of the studies that have been made in this field, have examined the different sources of irrigation in isolation from one another. In the present study, it is intended to examine the different sources of irrigation in an integrated manner and thus provide a macro-prospective as a guide to formulation of rational policies for irrigation management. In the present study, it is proposed to study the allocation of water by regions and crops and also over time. An attempt will be made to draw out policy implications and make some specific recommendations.