**5. Irrigation adaptation: water management and alternative water sources**

As freshwater resources are under increasing stress in several world regions, with a mismatch between availability and demand and temporal and geographical scales [44], new approaches have been promoted in order to guarantee the agricultural activity (by considering social and economic issues) and irrigation

*Irrigation - Water Productivity and Operation, Sustainability and Climate Change*

tion and sustainable management of natural resources [15].

**3. Irrigation operation: the need for being climate smart**

Agreement of the United Nations Framework Convention on Climate Change (UNFCCC)—entered into force on 2016 with the aim of, among others, recognizing the fundamental priority of safeguarding food security and ending hunger and reducing the particular vulnerabilities of food production systems to the adverse impacts of climate change. Furthermore, the Paris Agreement promotes better resilience of socioeconomic and ecological systems through economic diversifica-

Observed climate change impacts are already affecting food security through increasing temperatures, changing precipitation patterns, and greater frequency of some extreme events [16]. Increasing temperatures are affecting agricultural productivity in higher latitudes, raising yields of some crops (maize, cotton, and wheat), while yields of others are declining in lower-latitude regions [17]. Changes in land use and an increasing demand for water resources have affected the capacity of ecosystems to sustain food production, ensure freshwater resources supply, provide ecosystem services, and promote rural multifunctionality [18]. According to the special report "*Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and governance gas fluxes in terrestrial ecosystems*"—recently published by the Intergovernmental Panel on Climate Change (IPCC)—agriculture, forestry, and other land use (AFOLU) activities accounted for 23% of total net anthropogenic greenhouse gas emissions (GHGs) by the period 2007–2016. However, agriculture is not only a contributor to climate change, it will also be severely affected by climate change [19]. Moreover, some effects of warming on crop yields, increased pest occurrences, and the effects of extreme events (e.g., floods, storms, and droughts) on agricultural production are already observed [20]. Although farmers have long adapted to environmental conditions, the severity of the predicted climate changes may be beyond many farmers' current ability to adapt and improve their agricultural production systems and livelihoods [21]. While increased food production will have to be done in the face of a changing climate and climate variability [22], agricultural and irrigation systems should reduce their carbon cost and its contribution to GHG [23]. In order to address this gap, increasing interest has been focused on ensuring that both agriculture and irrigation become climate smart as a driven factor to ensure food security, improve rural livelihoods, and alleviate environmental risks for small-scale farmers [24]. The multi-dimensional aspects of agricultural production under climate change are captured by the climate-smart agriculture (CSA), an approach in which agriculture is transformed and reoriented under the projected scenarios of climate change [25]. The CSA has three concurrent objectives: (i) sustainably increasing farm productivity and income, (ii) increasing adaptive capacity to climate change, and (iii) reducing GHG emissions [26]. In fact, CSA seeks to enhance productivity, water conservation, livelihoods, biodiversity, resilience to climate stress, and environmental quality [27]. Despite the recognized importance of CSA by the Global Alliance for Climate Smart Agriculture (GASCA) and a range of international and national initiatives focused on climate-smart technologies (CST), the dissemination and uptake of climate smart technologies, tools, and practices is still largely an ongoing, challenging process [28]. At this

**2**

point, some questions should be addressed:

• To what extent is irrigation an enabler of other CSA technologies and under what conditions (soil/market/demography/crop/water management, etc.)?

sustainability (by addressing environmental issues) in an integrated way. The first approach is focused on putting more attention to understanding current water management and promoting transition to more adaptive water regimes that take into account environmental, technological, economic, institutional, and cultural characteristics of river basins. This implies a paradigm shift in water management from a prediction and control to a management as a social-learning approach [45]. The second approach has been focused on water availability. That is, the general decreasing trend in water availability and the need for sustainable use of available water resources have led regional and national governments worldwide to seek alternative water sources [46], putting special attention to wastewater reuse and water desalination. The first one is not a "new" water source, but rather a way to waste able to be used for a new water demand. It differs to increase water supply measures such as seawater desalination, which in effect includes a new input to the water cycle [47]. Both concepts, water reuse and seawater desalination, are limited by different key barriers. The first barrier is that their management is more complex than the management of conventional water resources, but also their cost is more expensive than the cost of "environmental" water sources—rivers—due to its conveyance, storage, and distribution in dedicated network infrastructure [48]. The second barrier is that both the public and farmers negatively percept alternative water sources by highlighting their environmental and health risks instead of their benefits (especially in the case of wastewater resources) [49–52]. Furthermore, although there are rules and regulations clearly focused on ensuring standards on food security, yuck factor currently justify the negative to use alternative water resources [53]. It should be noted that addressing the last two barriers are not solely related to technical issues, but to social issues. According to this and irrespective of scientific and engineering based considerations, farmers' opposition and public rejection has the potential to cause water reuse and water desalination projects to fail, before, during, or after their execution [54]. In fact, reuse and desalinated water schemes may face public opposition resulting from a combination of prejudiced beliefs, fear, attitudes, lack of knowledge, and general distrust, which, on the whole, is often not unjustified, judging by the frequent (and highly publicized) failures of wastewater treatment facilities worldwide.
