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A combination of a changing global climate coupled with rapid socio-economic development is putting unprecedented pressure on water, energy, and food resources. Addressing these issues within a nexus approach can help to identify appropriate management practices and strategic policies to ensure natural resources are used more sustainably thus avoiding exacerbating issues of water scarcity and food insecurity. In this study, we used an integrated water resource planning and irrigation model (WEAP) to assess emerging water-energy nexus issues on the Santa Elena peninsula in Ecuador. Simulated water demands showed that current water resources availability is insufficient to meet full irrigation requirements, especially during the dry season. Annual average energy demand for water conveyance in the SEP was significantly higher than for irrigation with 94.5 GWh and 13.5 GWh being used, respectively. Future challenges associated with changes in agricultural irrigation and urban demands within the SEP were evaluated using scenario analysis. This included considering various scenarios such as agricultural expansion, climate change, population growth, and a shift to export-oriented agriculture. The study underscores the significance of nexus thinking in guiding policy and decision-making in Santa Elena, although the limited data prevents its use in an operational framework. The benefits of adopting an integrated modelling approach to analyse water and energy nexus trade-offs are also discussed. [Display omitted] • An integrated reservoir simulation modelling approach for nexus analysis is used. • Water-energy nexus trade-offs during baseline and future scenarios are considered. • The system is unable to meet irrigation demand under baseline and all scenarios. • Energy demand for conveyance system is seven times higher than for irrigation. • Infrastructure expansion and more efficient agriculture needed if scenarios realise. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is one of the most important components in the hydrological cycle, and a key variable in hydrological modelling and water resources management. However, understanding the impacts of spatial variability in ET and the appropriate scale at which ET data should be incorporated into hydrological models, particularly at the regional scale, is often overlooked. This is in contrast to dealing with the spatial variability in rainfall data where existing guidance is widely available. This paper assesses the impacts of scale on the estimation of reference ET (ETo) by comparing data from individual weather stations against values derived from three national datasets, at varying resolutions. These include the UK Climate Impacts Programme 50 km climatology (UKCP50), the UK Met Office 5 km climatology (UKMO5) and the regional values published in the Agricultural Climate of England and Wales (ACEW). The national datasets were compared against the individual weather station data and the UKMO5was shown to provide the best estimate of ETo at a given site. The potential impacts on catchment modelling were then considered by mapping variance in ETo to show how geographical location and catchment size can have a major impact, with small lowland catchments having much higher variance than those with much larger areas or in the uplands. Some important implications for catchment hydrological modelling are highlighted.Editor D. Koutsoyiannis; Associate editor L. Ruiz [ABSTRACT FROM PUBLISHER]

Estimates of the magnitude and location of future irrigation demand are essential for strategic planning of water resources at national and regional levels. However, demand forecasting is fraught with difficulty, as water use for supplementary irrigation is highly sensitive to changes in agro-economic policy, climate and future water resources availability. Short-term forecasts are normally based on existing trends, modified by any expected variations. Following a long period of growth, the volume of water being abstracted for irrigation in England and Wales appears to be in decline. After allowing for annual weather variations, the underlying decline in dry year demand was -1.4% per annum from 1990 to 2010. Extrapolating these trends forward suggests a further reduction of around onequarter (-25%) by 2030. However longer-term forecasts (to the 2050s) need to consider alternative possible futures. The authors used a combination methodology to incorporate changes in population demographics, consumption and consumer preferences under a range of socioeconomic policies for four defined socioeconomic futures. The projected changes in 'unconstrained' demand in a dry year ranged from +40% to +167% by the 2050s; 'actual' water use will be constrained by water availability and allocation policy, which itself may lead to a relocation of demand. Combined with a probable decline in low-flow (summer) water availability, this indicates major future water resource issues. The figures need to be interpreted with caution as they are sensitive to model input values, and ignore impacts of stepchange genetic improvements and the effects of changing CO2 concentrations on crop growth. The differences between forecasts also highlight the sensitivity to assumptions and the potential impact of deeper-seated changes on current trends. Some policy options and potential adaptations are discussed. [ABSTRACT FROM AUTHOR]

Water is a fundamental component in primary food production, whether it be rainfall, irrigation used to water crops, or for supplying drinking water for animals, while the amount of water in the soil determines it capacity to support machinery and animals. We identify that UK agriculture is exposed to five main water-related risks: agricultural drought, scarcity of water resources, restrictions on the right to abstract water, excess soil water, and inundation. Projected milder, wetter winters and hotter, drier summers by the end of the century will change the frequency, persistence, or severity of each of these risks. This paper critically reviews and synthesizes the scientific literature on the impact of these risks on primary food production and the technological and managerial strategies employed to build resilience to these changing risks. At the farm scale, the emphasis has been on strategies to build robustness to reduce the impact of a water-related risk. However, collaborative partnerships allow for a more optimal allocation of water during times of scarcity. Enhancing cross-scale interactions, learning opportunities, and catchment-scale autonomy will be key to ensuring the agricultural system can build adaptive and transformational capacity. [ABSTRACT FROM AUTHOR]

• Maintaining 'headroom' in licensed allocations help minimise the risk of negative impacts from water shortages. • Increasing system redundancy confers robustness but conflicts with pressures to maximise efficiency. • Pursuit of robustness and efficiency locks systems into rigid production pathways. • Financial pressures force growers to focus on persistence of robust outputs at the cost of adaptability and transformability. Food production systems worldwide are increasingly exposed to water shortage shocks. Social-ecological resilience theory provides insights into the qualities which confer production systems with the capacity to absorb shocks and persist, undertake adaptations and ultimately achieve desirable transformations. Combining findings from the analysis of a set of 15 semi-structured interviews and 92 survey responses from growers in the UK, this paper uses resilience theory to explore the factors affecting exposure to the risk of water shortages, and management responses, within outdoor field vegetable production systems that depend on supplemental irrigation. The findings confirm that growers predominantly aim to build resilience by seeking to maintain a buffer or 'headroom' in their water resources to minimise the possibility that a shortage will disrupt their output of marketable produce and/ or lead to financial loss. This buffering strategy confers robustness by increasing system redundancy (availability of spare resources). But building-in redundancy conflicts with regulatory and supply chain pressures to maximise water and production efficiency respectively. Whilst stability of supply to consumers is, for the most-part, achieved, the discrepant pursuits of robustness and efficiency lock agricultural systems into increasingly rigid production and sales pathways, limiting capacities for adaptation and transformation - dimensions of resilience which permit successful system evolution in the context of more extreme shocks and stresses. [ABSTRACT FROM AUTHOR]