Cities are challenged by climate change impacts, such as extreme rainfall events that affect conventional urban water management systems via increased sewage water overflows resulting in water quality deterioration and urban floods causing infrastructure damage. Investments in blue–green infrastructure (BGI) are increasingly considered to address these issues. However, these should be cost-effective. In this study, the effectiveness of five different BGI strategies and one grey strategy are assessed for a peri-urban catchment area in Oslo (Grefsen) using a cost–benefit analysis. The strategies include (i) wadis; (ii) green roofs; (iii) raingardens, rain barrels and wadis; (iv) infiltration crates; (v) water squares, and (vi) a separate sewage system. Besides economic effectiveness, the study also aims to identify the proper protection level by comparing cost–benefit ratios and net benefits for 60-min rainfall events occurring once every 5, 20, and 100 years (M5, M20, and M100), concerning both the current situation and under future climate change (using the Representative Concentration Pathway 8.5). The analyses revealed the highest BC ratios for wadis (12.0–17.3), separate sewage systems (7.7–15.1), and a combination of raingardens, rain barrels, and wadis (1.6–2.3). Strategies dimensioned for less frequent but more intensive rainfall events yielded higher BC ratios. Results for infiltration crates were difficult to interpret and were found to be very sensitive to input parameters. The other strategies implied a negative BC ratio. The study concludes that investments in BGI in Grefsen, Oslo, can be positively judged from a social–economic perspective and provide suitable information for water-related decision makers to decide upon the strategy selection and the appropriate flood protection level.

Food system analysis in arid and semi-arid countries inevitably meets water availability as a major constraining food system driver. Many such countries are net food importers using food subsidy systems, as water resources do not allow national food self-sufficiency. As this leaves countries in a position of dependency on international markets, prices and export bans, it is imperative that every domestic drop of water is used efficiently. In addition, policies can be geared towards ‘water footprints’, where water use efficiency is not just evaluated at the field level but also at the level of trade and import/export. In this paper, Egyptian food systems are described based on production, distribution and consumption statistics, key drivers and food system outcomes, i.e., health, sustainable land and water use, and inclusiveness. This is done for three coarsely defined Egyptian food systems: traditional, transitional and modern. A water footprint analysis then shows that for four MENA countries, differences occur between national green and blue water volumes, and the volumes imported through imported foods. Egypt has by far the largest blue water volume, but on a per capita basis, other countries are even more water limited. Then for Egypt, the approach is applied to the wheat and poultry sectors. They show opportunities but also limitations when it comes to projected increased water and food needs in the future. An intervention strategy is proposed that looks into strategies to get more out of the food system components production, distribution and consumption. On top of that food subsidy policies as well as smart water footprint application may lead to a set of combined policies that may lead to synergies between the three food system outcomes, paving the way to desirable food system transformation pathways.

The Vietnamese Mekong Delta (VMD) is the main agricultural production region in Vietnam producing rice, fruits, shrimps, livestock among a variety of crops. The current VMD agricultural production system (APS) is under threat from sea level rise aggravated by climate change causing further inland salinity intrusion. Transition pathways towards increased salinity adaptation in APSs are therefore required to maintain food security. This study assesses the present water sources usage for APSs and associated quality, quantity and food safety issues. Water-related stresses observed by farmers in the coastal Tra Vinh region are described based on a focus group discussion and in-depth household interviews. Multiple water sources were described for agricultural practices (e.g., surface water, deep well, rainwater) which differed per season. Also, farmers reported to be affected by salinity (67.3%) and groundwater shortages (28.8%) hampering current agricultural production. Solutions and adaptations foreseen vary from more efficient irrigation, dropping crops and new practices and in a lesser brackish water farming systems or moving to new places and transfer to new jobs. Subsequently, transition pathways focusing on salinity adaptation to maintain food security are proposed from a water- and soil management perspective and include i) irrigation innovations to produce crops under more scarce fresh water availability, ii) freshwater storage as a buffer in dry season; iii) basic water treatment options to make water brackish/saline water suitable for livestock and iv) increase soil organic content which can improve soil water retention and reduce impacts of salinity on crops. It is recommended to test multiple transition pathways on farm level in representative regions in the VMD through living labs or demonstration farms.