Projecting extreme droughts in rapidly changing human-water systems

在英国，可靠的供水通常被认为是理所当然的。然而，供水压力越来越大。到2050年，人为气候变化和不断增长的人口对水的需求预计将导致英国各地频繁出现水资源短缺，预测估计，为了确保供应，每天需要额外增加30亿升水。极端干旱可能超出许多自来水公司的应对能力，导致严格的供水限制，仅紧急供水措施就耗资高达400亿加元。预测可能出现的“最坏情况”干旱及其对河流流量的影响，对于检验当前供水系统的复原力、支持未来对供应基础设施(如水库、海水淡化厂、集水区间输水计划)的投资等关键规划决策以及确保未来为粮食-能源-水系统提供充足的水供应至关重要。这是一项挑战，因为目前对淡水资源将如何应对水供应和水需求变化的了解仍然很少，也很难量化，特别是对于极端干旱事件。这个问题是双重的。首先，我们目前用来为水资源决策提供信息的模型忽视了人类用水(如水库蓄水、灌溉、水力发电)和陆地水通量(如坡面径流、地表水和地下水流动)之间的关键相互作用。其次，这种极端干旱事件尤其难以描述和预测。干旱是复杂的现象，跨越多个时空尺度，从小河流到大陆尺度，持续数周到数十年。这项研究通过建立英国各地水系对极端干旱的适应能力来应对这些挑战。它将开发新的综合建模工具，并利用独特的人类用水数据集，以确定淡水资源(河流流量和地下水位)将如何应对水供应(人为气候变化)和水需求(人类用水)的变化。综合模拟框架将明确描述人类用水(来自家庭、农业和工业需求)与水文-气候过程(陆地-大气、山坡径流和地表水-地下水相互作用)之间的相互作用和反馈。这将被用来促进英国干旱预测的阶段性变化，并对人类-水相互作用如何缓解或加强水文干旱产生新的理解，这些干旱将被提供给下一代地球系统模型。我将开发全国统一的、开放访问的气象和水文干旱事件资料库，以提供英国首个极端干旱预测，说明未来水供需的变化。这些新的数据集将被用来支持有关如何与包括水务公司、区域规划组织、监管机构和研究机构在内的主要项目合作伙伴合作，最好地管理未来水资源的关键决策。

A reliable water supply is usually taken for granted in the UK. However, there is increasing pressure on water supplies. By 2050, anthropogenic climate change and increasing water demand from a growing population is projected to lead to frequent water shortages across the UK, with projections estimating more than 3 billion litres of additional water a day required to ensure supply. An extreme drought could exceed the coping capacity of many water companies leading to severe supply restrictions and costing up to £40 billion in emergency water supply measures alone. Predicting plausible 'worst case' droughts and their impacts on river flows is vital to test the resilience of current water supply systems, to support critical planning decisions such as future investment in supply infrastructure (e.g. reservoirs, desalination plants, inter-catchment water transfer schemes) and to ensure adequate future water supply for food-energy-water systems. This is a challenge as current understanding of how freshwater resources will respond to changes in water supply and water demand remain poorly understood and quantified, particularly for extreme drought events. The problem is two-fold. Firstly, the models we currently use to inform water resource decisions currently neglect key interactions between human water-use (such as reservoir storage, irrigation, hydro-power generation) and terrestrial water fluxes (such as hillslope runoff, surface water and groundwater flow). Secondly, such extreme drought events are especially difficult to characterise and predict. Droughts are complex phenomena that vary across multiple spatial and temporal scales from small river reaches to continental scales lasting for weeks to decades.This research addresses these challenges by establishing the resilience of water systems across Great Britain to extreme droughts. It will develop new integrated modelling tools and leverage unique datasets of human-water use to determine how freshwater resources (river flows and groundwater levels) will respond to changes in water supply (from anthropogenic climate change) and water demand (from human water use). The integrated modelling framework will explicitly characterise the interactions and feedbacks between human-water use (from domestic, agricultural and industrial demand) and hydro-climatic processes (land-atmosphere, hillslope runoff and surface-groundwater interactions). This will be used to facilitate a step-change in UK drought prediction and generate new understanding of how human-water interactions alleviate or enhance hydrological droughts that will feed into the next generation of earth system models. I will develop nationally consistent, open access libraries of meteorological and hydrological drought events to provide the first extreme drought projections for Great Britain that account for changes in future water supply and demand. These new datasets will be used to support critical decisions on how best to manage future water resources in collaboration with key project partners including water companies, regional planning groups, regulatory bodies and research institutes.