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，水供应的压力越来越大。到2050年，人为的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，预计每天需要超过30亿升的额外水来确保供应。一场极端干旱可能超出许多供水公司的应对能力，导致严重的供水限制，仅在紧急供水措施上就耗资高达400亿英镑。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测试当前供水系统的复原力、支持关键的规划决策（如未来对供水基础设施的投资（例如水库、海水淡化厂、集水区间调水计划）以及确保未来粮食-能源-水系统的充足供水）至关重要。这是一个挑战，因为目前对淡水资源如何对水供应和水需求的变化作出反应的理解仍然很差，而且无法量化，特别是对极端干旱事件。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目前忽视了人类用水（如水库储存、灌溉、水力发电）和陆地水通量（如山坡径流、地表水和地下水流动）之间的关键相互作用。其次，这种极端干旱事件特别难以描述和预测。干旱是一种复杂的现象，在多个空间和时间尺度上发生变化，从小河流到大陆尺度，持续数周到数十年。这项研究通过建立整个英国的水系统对极端干旱的恢复能力来解决这些挑战。它将开发新的综合建模工具，并利用人类用水的独特数据集来确定淡水资源（河流流量和地下水水位）将如何响应供水（来自人为气候变化）和水需求（来自人类用水）的变化。综合模型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。这将用于促进英国干旱预测的逐步变化，并对人类与水的相互作用如何减轻或加强水文干旱产生新的理解，这将为下一代地球系统模型提供信息。我将在全国范围内建立一致的、开放的气象和水文干旱事件图书馆，为英国提供第一个极端干旱预测，说明未来水供应和需求的变化。这些新的数据集将用于支持与关键项目伙伴（包括水务公司、区域规划组织、监管机构和研究机构）合作，就如何最好地管理未来水资源做出关键决策。

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.