The need for achieving efficient and sustainable use of water resources is pressing, however, this often requires better understanding of the potential of water conservation, taking into account the impact on return flows, and the costs in relation to sectoral benefits. Using modelling and limited observational data we explore the costs and potential water savings of 24 combinations of water conservation measures in the Rufiji basin, Tanzania. We compare these costs with estimates of the value such water savings could generate from water use in three important economic sectors; agriculture, energy and downstream ecosystems with high tourism potential. The cost of water conservation measures (median: 0.07 USD m−3) is found to be: higher than the value of most uses of water for agriculture (growing crops in expanded irrigation sites) and the median value for hydropower generation (from a new mega dam currently under construction); and lower than the ecosystem value. Nevertheless, under our modelling assumptions, the volume of additional water required to supply planned irrigation expansion in the basin could be reduced by 1.5 BCM using water conservation methods that would be financially viable, given the value of competing uses of water. Water savings of this magnitude would reduce potential trade-offs between use of water for hydropower and ecosystem services, by allowing peak environmental flow releases even in dry years, and without reducing firm energy generation. This methodology is transferable and relevant for producing realistic assessments of the financial incentives for long-term sustainable water use in agriculture, given incentives for other uses. With most reservoirs now being built for multiple purposes improved understanding of trade-offs between different sectors and functions is needed.

Urbanisation will be one of the 21st century's most transformative trends. By 2050, it will increase from 55% to 68%, more than doubling the urban population in South Asia and Sub-Saharan Africa. Urbanisation has multifarious (positive as well as negative) impacts on the wellbeing of humans and the environment. The 17 UN Sustainable Development Goals (SDGs) form the blueprint to achieve a sustainable future for all. Clean Water and Sanitation is a specific goal (SDG 6) within the suite of 17 interconnected goals. Here we provide an overview of some of the challenges that urbanisation poses in relation to SDG 6, especially in developing economies. Worldwide, several cities are on the verge of water crisis. Water distribution to informal settlements or slums in megacities (e.g. N50% population in the megacities of India) is essentially non-existent and limits access to adequate safe water supply. Besides due to poor sewer connectivity in the emerging economies, there is a heavy reliance on septic tanks, and other on-site sanitation (OSS) system and by 2030, 4.9 billion people are expected to rely on OSS. About 62–93% of the urban population in Vietnam, Sri Lanka, the Philippines and Indonesia rely on septic tanks, where septage treatment is rare. Globally, over 80% of wastewater is released to the environment without adequate treatment. About 11% of all irrigated croplands is irrigated with such untreated or poorly treated wastewater. In addition to acute and chronic health effects, this also results in significant pollution of often-limited surface and groundwater resources in Sub-Saharan Africa and Asia. Direct and indirect water reuse plays a key role in global water and food security. Here we offer several suggestions to mitigate water and food insecurity in emerging economies.

West Africa's rice imports currently satisfy 70% of the soaring local demand, worsening the food vulnerability of an increasingly urbanized population. Despite considerable rice-growing potential, lack of water control systems, access to improved seeds, agrochemicals and appropriate mechanization have resulted in modest production growth rates, unable to alter the region's dependency on imported rice. Governments aim to boost production with import duties and input subsidies. However, questions remain as to whether these policies enable the rice sector to respond to changing consumers preferences for high grade rice and to contribute to national economic growth. We present the results from a Policy Analysis Matrix (PAM) on rice production in Ghana, Burkina Faso and Niger and under three water management systems: irrigation (public scheme), supplemented rain-fed (rainfall aided by autonomously-sourced water supplies) and purely rain-fed. Our results show that policy interventions in these West African countries (i.e., input subsidies and import taxes) did not significantly enhance the profitability of rice production to farmers due to the effect of market failures (limited capital access and non-competitive market for rice) and the low quality of local milled rice. The PAM results point strongly to the importance of improving rice quality and yields through more efficient water management and post-harvest handling/processing and targeted breeding to match consumers' preferences.

West Africa's rice imports currently satisfy 70% of the soaring local demand, worsening the food vulnerability of an increasingly urbanized population. Despite considerable rice-growing potential, lack of water control systems, access to improved seeds, agrochemicals and appropriate mechanization have resulted in modest production growth rates, unable to alter the region's dependency on imported rice. Governments aim to boost production with import duties and input subsidies. However, questions remain as to whether these policies enable the rice sector to respond to changing consumers preferences for high grade rice and to contribute to national economic growth. We present the results from a Policy Analysis Matrix (PAM) on rice production in Ghana, Burkina Faso and Niger and under three water management systems: irrigation (public scheme), supplemented rain-fed (rainfall aided by autonomously-sourced water supplies) and purely rain-fed. Our results show that policy interventions in these West African countries (i.e., input subsidies and import taxes) did not significantly enhance the profitability of rice production to farmers due to the effect of market failures (limited capital access and non-competitive market for rice) and the low quality of local milled rice. The PAM results point strongly to the importance of improving rice quality and yields through more efficient water management and post-harvest handling/processing and targeted breeding to match consumers' preferences.

Recycling of food-by-products is very important subject. Many trials have been done to reuse by-product, however, almost trials have not been to install the commercial process due to their treatment costs and their qualities. To convert biodegradable stuff is one of their trail fields. However, their products have disadvantage of high cost and low properties against water-resistance. To minimize costs and to improve waterproof property, we used zein-containing corn gluten meal and succeeded in making solid materials by injection molding. We turned the materials into pellets with an extruder, and then molded the pellets into seedling culture pots with an injection molder. This study project was carried out jointly with Showa Sangyo Co., The Japan Steel Works and National Food Research Institute. In this project we were able to successfully reduce costs and to obtain solid molded products for practical use by adopting the injection molding method, which has many advantages in productivity (low costs, high moldability, flexibility to make various shapes of molds). At present, we are working to assess the biodegradable molded material actually applied and to improve materials for different purposes.