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Drought and water scarcity pose a risk to the economy, particularly sectors where water is a crucial input to the production process. This paper describes integrated simulations of water shortages from a dynamic national water resource systems model with a static economic input‐output (I‐O) model to assess total drought risk to the economy. To quantify the economic risks of drought and water scarcity, the analysis: (a) integrates a large ensemble of simulated meteorological droughts, propagated through a national hydrological model and water resource systems model to simulate water availability from reservoirs and groundwater; (b) assesses implications of restrictions on water availability for multiple water user categories, representing natural and human contributions to water scarcity; (c) investigates how water shortages propagate into economy‐wide direct and indirect impacts. The study focuses on England and Wales where the water supply system is considered under strain, with growing recognition of the economic risk of prolonged and widespread shortages. The direct Expected Annual Loss (EAL) to water users, averaged over an ensemble equivalent to 2800 years of synthetic daily weather, is estimated to be £11.7 million in the 2011 base‐year. Accounting for indirect economic losses results in a total EAL of £30.2 million in 2011. The most severe event simulated results in a total loss of £1.4 billion in 2011, equivalent to 0.11% of GVA. The analysis provides a framework to assess what the economically efficient level of system reliability should be, and for deciding upon appropriate water management regulations and strategic investments. Key Points: Simulated water availability from a national water resource system model are integrated with a macroeconomic model to assess drought riskThe use of a large ensemble of synthetic drought simulations supports the risk‐based analysis of direct and indirect economic lossesThe method supports national economic assessment of the implications of climate change and different water management strategies [ABSTRACT FROM AUTHOR]

In the established climate, evaporation dominates eastern England's water regime, taking it near to desiccation in dry summers. Now, hotter drier summers are predicted - even more evaporation, coupled with less rainfall. If true, the reduction in summer water will be very large - far more than all abstractions put together, even by the 2020s. Thereafter, summer droughts will intensify and spread westwards, threatening river flows, agriculture and natural vegetation. In particular, irrigation need will escalate, with no summer water to meet it - a climate change impact that is being underperceived. This paper explores the scale of the issues and the adaptation options. It demonstrates synergy between the interests of agriculture and of water supply and calls for integrated strategic planning, with reservoirs and reuse high on the adaptation agenda. [ABSTRACT FROM AUTHOR]

Resilient water supplies in England need to be secured in the face of challenges of population growth, climate change and environmental sustainability. We propose a blueprint for water resources planning that uses system simulation modelling to estimate the frequency, duration and severity of water shortages at present and in the context of future plans and scenarios. We use multiobjective optimisation tools to explore trade‐offs between these risk metrics and cost of alternative plans, and we use sensitivity analysis to identify plans that robustly achieve targets for tolerable risk, alongside other performance objectives. The results of a case study in the Thames basin demonstrate that the proposed methodology is feasible given commonly available data sets and models. The proposed method provides evidence with which to develop water resource management plans that demonstrably balance the risks of water shortages, costs to water users and environmental constraints in an uncertain future. [ABSTRACT FROM AUTHOR]

Water resources planning and management by water utilities have traditionally been based on consideration of water availability. However, the reliability of public water supplies can also be influenced by the quality of water bodies. In this study, we proposed a framework that integrates the analysis of risks of inadequate water quality and risks of insufficient water availability. We have developed a coupled modeling system that combines hydrological modeling of river water quantity and quality, rules for water withdrawals from rivers into storage reservoirs, and dynamical simulation of harmful algal blooms in storage reservoirs. We use this framework to assess the impact of climate change, demand growth, and land‐use change on the reliability of public water supplies. The proposed method is tested on the River Thames catchment in the south of England. The results show that alongside the well‐known risks of rising water demand in the south of England and uncertain impacts of climate change, diffuse pollution from agriculture and effluent from upstream waste water treatment works potentially represent a threat to the reliability of public water supplies in London. We quantify the steps that could be taken to ameliorate these threats, though even a vigorous pollution‐prevention strategy would not be sufficient to offset the projected effects of climate change on water quality and the reliability of public water supplies. The proposed method can help water utilities to recognize their system vulnerability and evaluate the potential solutions to achieve more reliable water supplies. Key Points: Proposes an integrated water quality‐quantity model,including abstraction rules and reservoir water quality,for PWS reliability assessmentAssesses the impact of land‐use change, and potential mitigations, on water supply reliabilityApplies a novel climate dataset to explore hydrological variability and change [ABSTRACT FROM AUTHOR]

Drought frequency and intensity is expected to increase in many regions worldwide, and water shortages could become more extreme, even in humid temperate climates. To protect the environment and secure water supplies, water abstractions for irrigation can be mandatorily reduced by environmental regulators. Such abstraction restrictions can result in economic impacts on irrigated agriculture. This study provides a novel approach for the probabilistic risk assessment of potential future economic losses in irrigated agriculture arising from the interaction of climate change and regulatory drought management, with an application to England and Wales. Hydrometeorological variability is considered within a synthetic data set of daily rainfall and river flows for a baseline period (1977–2004) and for projections for near future (2022–2049) and far future (2072–2099). The probability, magnitude, and timing of abstraction restrictions are derived by applying rainfall and river flow triggers in 129 catchments. The risk of economic losses at the catchment level is then obtained from the occurrences of abstraction restrictions combined with spatially distributed crop‐specific economic losses. Results show that restrictions will become more severe, more frequent, and longer in the future. The highest economic risks are projected where drought‐sensitive crops with a high financial value are concentrated in catchments with increasingly uncertain water supply. This research highlights the significant economic losses associated with mandatory drought restrictions experienced by the agricultural sector and supports the need for environmental regulators and irrigators to collaboratively manage scarce water resources to balance environmental and economic considerations. Plain Language Summary: Droughts are expected to become more common in many regions worldwide due to climate change. During droughts events, environmental regulators can impose water abstraction restrictions for irrigation to protect drinking water supplies and meet the minimum water requirements for the natural environment. This study provides a novel approach to evaluate the risk of economic losses in irrigated agriculture due to water abstraction restrictions implemented during current and future drought conditions under climate change, using England and Wales as a case study. A data set of modeled daily rainfall and river flow for a baseline period (1977–2004) and for near future (2022–2049) and far future (2072–2099) is used. Decisions regarding when to implement restrictions in 129 catchments are made considering a set of rainfall and river flow thresholds, with the associated economic losses calculated by crop type. Results show that in the future water abstraction restrictions for irrigation will become more severe, more frequent, and longer. The highest economic losses will affect the most drought‐sensitive crops, which are located in water stressed catchments and have a high financial value in the food market. This research highlights the importance of a collaborative work between environmental regulators and irrigators to manage scarce water resources and balance environmental and economic considerations under drought. Key Points: A novel probabilistic approach of the risk of economic losses in irrigated agriculture due to climate change and drought management is shownFuture water restrictions on irrigation in England and Wales are projected to increase in duration, severity, and frequencyHydroclimatic variability, drought management, and the distribution and sensitivity of crops to water stress shape the economic impacts [ABSTRACT FROM AUTHOR]

Although the climate change projections are produced by global models, studying the impact of climatic change on water resources is commonly investigated at catchment scale where the measurements are taken, and water management decisions are made. For this study, the Frome catchment in the UK was investigated as an example of midland England. The DiCaSM model was applied using the UKCP09 future climate change scenarios. The climate projections indicate that the greatest decrease in groundwater recharge and streamflow was projected under high emission scenarios in the 2080s. Under the medium and high emission scenarios, model results revealed that the frequency and severity of drought events would be the highest. The drought indices, the Reconnaissance Drought Index, RDI, Soil Moisture Deficit, SMD and Wetness Index, WI, predicted an increase in the severity of future drought events under the high emission scenarios. Increasing broadleaf forest area would decrease streamflow and groundwater recharge. Urban expansion could increase surface runoff. Decreasing winter barley and grass and increasing oil seed rape, would increase SMD and slightly decrease river flow. Findings of this study are helpful in the planning and management of the water resources considering the impact of climate and land use changes on variability in the availability of surface and groundwater resources. [ABSTRACT FROM AUTHOR]