Africa’s Nile basin countries should invest in rain, not big infrastructure projects

South Sudan could export as much as $1.8 billion in rain-fed food products, writes Christian Sideriu

Advances in global hydrology–crop modelling to support the UN’s Sustainable Development Goals in South Asia

Achieving the United Nation's Sustainable Development Goals (SDG) in the context of a rapidly changing climate and demographics is one of the major challenges for South Asia. Interventions aimed at achieving the SDGs will be varied and are likely to contain basin-wide trade-offs that need to be understood. In this paper, we synthesize recent global hydrology-crop model developments, with a specific focus on human impact parameterisations like the management of human built storage capacity, irrigation withdrawal and supply, and irrigation efficiency. We show that these models can help improve our understanding of the composition and flows of water, and the linkages between water scarcity and food production. To fully exploit the potential of improved models for policy support and the design of pathways towards SDG achievement, we envisage scope to include more local data from test fields and pilot sites, use the models to derive biophysical and financial feasibility of interventions, and improve the interaction with policy-makers and regional stakeholders through the development of better communication and visualisation tools

When do Indians feel hot? Internet searches indicate seasonality suppresses adaptation to heat

In a warming world an increasing number of people are being exposed to heat, making a comfortable thermal environment an important need. This study explores the potential of using Regional Internet Search Frequencies (RISF) for air conditioning devices as an indicator for thermal discomfort (i.e. dissatisfaction with the thermal environment) with the aim to quantify the adaptation potential of individuals living across different climate zones and at the high end of the temperature range, in India, where access to health data is limited. We related RISF for the years 2011–2015 to daily daytime outdoor temperature in 17 states and determined at which temperature RISF for air conditioning starts to peak, i.e. crosses a 'heat threshold', in each state. Using the spatial variation in heat thresholds, we explored whether people continuously exposed to higher temperatures show a lower response to heat extremes through adaptation (e.g. physiological, behavioural or psychological). State-level heat thresholds ranged from 25.9 °C in Madhya Pradesh to 31.0 °C in Orissa. Local adaptation was found to occur at state level: the higher the average temperature in a state, the higher the heat threshold; and the higher the intra-annual temperature range (warmest minus coldest month) the lower the heat threshold. These results indicate there is potential within India to adapt to warmer temperatures, but that a large intra-annual temperature variability attenuates this potential to adapt to extreme heat. This winter 'reset' mechanism should be taken into account when assessing the impact of global warming, with changes in minimum temperatures being an important factor in addition to the change in maximum temperatures itself. Our findings contribute to a better understanding of local heat thresholds and people's adaptive capacity, which can support the design of local thermal comfort standards and early heat warning systems

Water conservation can reduce future water-energy-food-environment trade-offs in a medium-sized African river basin

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

Cost and effectiveness of in-season strategies for coping with weather variability in Pakistan's agriculture

Crops are vulnerable to weather hazards throughout the growth season, with periods of heightened risk described as critical moments. Farmers have a number of ex-ante and in-season options for coping with these events, and ex-post adjustments to farm-household portfolios to further limit the impact on livelihoods if these options fail. Adaptation-related research has focussed mainly on ex-ante or ex-post coping strategies, because in-season approaches tend to be seen as a given, meaning their cost effectiveness is ignored. Based on detailed survey data collected from 287 households in four of the main cropping systems in Pakistan, this study evaluates the impact pathways of hazards and the cost effectiveness of in-season coping strategies. Yield losses varied by 10–30% for 43% of the cases and by 31–50% for another 39%, with the most severe losses caused by the compounding effect of two hazards in one crop season or if both crops in a multi-crop rotation were affected simultaneously. In-season coping options were mostly restricted to the early crop stages and constrained by a short window of time for the response. The application of in-season coping strategies resulted in a yield recovery of 40–95%, with an additional cost of 4–34% of the value of recovered yield. The major critical moments identified were the harvest season, with farming often affected by un-seasonal precipitation, and the germination stage, with an additional high risk for low temperatures at high altitude. A better understanding of the differentiated risks and effectiveness of in-season coping strategies could support the promotion of sustainable crop production in similar agro-ecologies. Moreover, the effectiveness of present-day coping strategies, rather than the use of coping approaches itself, could signal a potential ability to adjust to future climate change

Multi-scale analysis of the water-energy-food nexus in the Gulf region

We quantify the heavily oil-dominated WEF nexus in three Gulf Cooperation Council (GCC) countries (Kuwait, Qatar and Saudi Arabia) across spatial scales and over time, using available empirical data at the national level, and explore the exposure to nexus stresses (groundwater depletion) in other countries through virtual water trade. At the domestic scale, WEF trade-offs are fairly limited; while all sectors require considerable amounts of energy, the requirements for water and food production are modest compared to other uses. At the international scale, revenues from oil exports in the GCC allow the region to compensate for low food production and scarce water availability. This dependency is dynamic over time, increasing when oil prices are low and food prices are high. We show how reducing domestic trade-offs can lead to higher exposure internationally, with rice imports originating in regions where groundwater is being depleted. However, Saudi Arabia’s increased wheat imports, after reversing its food self-sufficiency policy, have had limited effects on groundwater depletion elsewhere. Climate change mitigation links the WEF nexus to the global scale. While there is great uncertainty about future international climate policy, our analysis illustrates how implementation of measures to account for the social costs of carbon would reduce the oil and gas revenues available to import food and desalinate water in the GCC

Multi-scale analysis of the water-energy-food nexus in the Gulf region

We quantify the heavily oil-dominated WEF nexus in three Gulf Cooperation Council (GCC) countries (Kuwait, Qatar and Saudi Arabia) across spatial scales and over time, using available empirical data at the national level, and explore the exposure to nexus stresses (groundwater depletion) in other countries through virtual water trade. At the domestic scale, WEF trade-offs are fairly limited; while all sectors require considerable amounts of energy, the requirements for water and food production are modest compared to other uses. At the international scale, revenues from oil exports in the GCC allow the region to compensate for low food production and scarce water availability. This dependency is dynamic over time, increasing when oil prices are low and food prices are high. We show how reducing domestic trade-offs can lead to higher exposure internationally, with rice imports originating in regions where groundwater is being depleted. However, Saudi Arabia's increased wheat imports, after reversing its food self-sufficiency policy, have had limited effects on groundwater depletion elsewhere. Climate change mitigation links the WEF nexus to the global scale. While there is great uncertainty about future international climate policy, our analysis illustrates how implementation of measures to account for the social costs of carbon would reduce the oil and gas revenues available to import food and desalinate water in the GCC

Assessing river basin development given water-energy-food-environment interdependencies

Many river basins in the Global South are undergoing rapid development with major implications for the interdependent water-energy-food-environmental (WEFE) ‘nexus’ sectors. A range of views on the extent to which such natural-human systems should be developed typically exist. The perceived best investments in river basins depend on how one frames the planning problem. Therefore, we propose an approach where the best possible (optimised) implementations of different river basin development scenarios are assessed by comparing their WEFE sector trade-offs. We apply the approach to Tanzania’s river basin, an area with multiple WEFE interdependencies and high development potential (irrigation and hydropower) and ecosystem services. Performance indicators are identified through stakeholder consultation and describe WEFE sector response under scenarios of river basin development. Results show considerable potential exists for energy and irrigation expansion. Designs that prioritise energy production adversely affect environmental performance, however, part of the negative impacts can be minimised through release rules designed to replicate the natural variability of flow. The reliability of monthly energy generation is more sensitive to environmental-oriented management than the cumulative annual energy production. Overall results highlight how sectoral trade-offs change depending on the extent of development, something that may be difficult to regulate in the future, and that there are important basin-scale interdependencies. Benefits and limitations of the approach and its application are discussed

Crop-specific seasonal estimates of irrigation-water demand in South Asia

This work was carried out by the Himalayan Adaptation, Water and Resilience (HI-AWARE) consortium under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA), with financial support from the UK Government’s Department for International Development and the International Development Research Centre, Ottawa, Canada. We acknowledge the Potsdam Institute for Climate Impact Research for their support in using the LPJmL model and computational facilities.Especially in the Himalayan headwaters of the main rivers in South Asia, shifts in runoff are expected as a result of a rapidly changing climate. In recent years, our insight into these shifts and their impact on water availability has increased. However, a similar detailed understanding of the seasonal pattern in water demand is surprisingly absent.This hampers a proper assessment of water stress and ways to cope and adapt. In this study, the seasonal pattern of irrigation-water demand resulting from the typical practice of multiple cropping in South Asia was accounted for by introducing double cropping with monsoon-dependent planting dates in a hydrology and vegetation model. Crop yields were calibrated to the latest state-level statistics of India, Pakistan, Bangladesh and Nepal. The improvements in seasonal land use and cropping periods lead to lower estimates of irrigation-water demand compared to previous model-based studies, despite the net irrigated area being higher. Crop irrigation-water demand differs sharply between seasons and regions; in Pakistan, winter (rabi) and monsoon summer (kharif) irrigation demands are almost equal, whereas in Bangladesh the rabi demand is 100 times higher. Moreover, the relative importance of irrigation supply versus rain decreases sharply from west to east. Given the size and importance of South Asia improved regional estimates of food production and its irrigation-water demand will also affect global estimates. In models used for global water resources and food-security assessments, processes like multiple cropping and monsoon-dependent planting dates should not be ignored

Going local: evaluating and regionalizing a global hydrological model’s simulation of river flows in a medium-sized East African basin

Study region: The Rufiji basin, East Africa. Study focus: Rapid advances in global hydrological model (GHM) resolution, model features, and in situ and remotely sensed datasets are driving progress towards local relevance and application. Despite their increasing use, however, evaluation of local hydrological performance of GHMs is rare. In this paper, we examine the performance of a well-known GHM (LPJmL, recently modified to ∼9 km resolution) with and without modest steps to regionalise the model. We consider the Rufiji river basin, an economically important medium-size basin in eastern Africa. New hydrological insights for the region: Our results indicate that the unmodified GHM does provide a reasonable first approximation of spatial variability in mean flow conditions, but scores rather poorly on seasonal and inter-annual variability. For the model to achieve levels of performance indicators comparable with bespoke modelling, modifications to model inputs, additional runoff delay and wetland parameterization were required. The largest improvements are associated with adjustments in precipitation and enhanced runoff delay. With the modified version, as a proof of concept, we show that a well-known drying trend in a major tributary of the Rufiji can be explained by implementing irrigation abstractions in the model. Overall, the results suggest that with limited and fairly simple modification GHMs can be regionalised to allow their use for scenario testing and further exploration of key local processes in basins with limited observational data