Deplete and Retreat: The Future of Andean Water Towers

耗尽与撤退：安第斯水塔的未来

• 批准号: NE/X003507/1
• 负责人: Gareth Old
• 金额: $ 5.73万
• 依托单位: UK CENTRE FOR ECOLOGY & HYDROLOGY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX003507%2F1
• 关键词: Deplete; Retreat; Future; Andean; Water

Life on land depends upon freshwater. Mountains act as water towers, producing water by lifting moist air, and by providing temporary surface and below-ground storage of water for later release into rivers. These stores are particularly important in regions that experience seasonal droughts, as snow and ice melt can counteract reduced rainfall during dry spells. Two main natural depots of frozen water exist. Snow is a short-term store, delaying the release of water after snowfall on daily to seasonal timescales. Ice melt also releases water seasonally. However, glacier ice is a longer-term reservoir, storing water for decades to centuries. A similar behaviour can be observed in the non-frozen part of a mountain catchment. Stores such as wetlands, ponds and shallow below-ground flow provide short-term storage, while lakes and deeper groundwater show long-term release characteristics.The combination of these different processes determines the magnitude and behaviour of a mountain range's water tower function for the surrounding area. This is particularly important in the Andes, where some of the most important water towers of the globe are found. The human population in regions neighbouring the Andes depend on mountain water resources for drinking, food production and hydropower, as do animals and plant life.Unfortunately, human-induced climate change is altering the stores of water held in the Andes water towers. Greenhouse gas emissions mean that snow-bearing weather conditions are becoming less frequent, depleting the stocks of snow held in the mountains. The lack of replenishing snow, and increasing temperatures, are causing glaciers to lose the ice they store, retreating to the higher and colder portions of the mountains. In combination with climate change impacts on the rest of the catchment, this is contributing to water shortages across the Andes. Ongoing droughts are hitting high-population cities, where the concentration of people increases the demand for water. For example, the cities of Lima and Huaraz (Peru), La Paz (Bolivia) and Santiago (Chile), are all situated in catchments where snow and ice melt contribute to river flow. However, upstream rural areas, which are less adaptable to climate change, are often even more directly reliant upon snow and ice meltwater. This impacts irrigation for agriculture, stressing the food security of the region.To help manage these changes to water supplies, this project aims to achieve two things. The first is to provide better monitoring. The high altitudes of the Andes are poorly instrumented. To work out where and how fast conditions are changing, we will install more scientific instruments to measure snow, weather and river discharge. To contextualise the changes we can measure now, we need longer observational records extending back in time. Many glaciers have been retreating since 1850, leaving behind an imprint in the landscape which we will map. Using satellite imagery, we can track the retreat of these glaciers from the 1970s to their present position. We will also utilise records of past climate conditions, recorded by sailors in ships-log books and stored in the landscape in sediments. Our second goal is to project future changes, which requires computer models of climate, glacier and river processes. Such projections are required for policy makers, who need to be reliably informed of potential future change. We will combine state-of-the-art models, to simulate the changing water resources in ten Andean catchments. To assess the skill of our models at making predictions, we will test them against our observations of past conditions and current changes. Models that perform well at replicating observed conditions will be used to project a range of possible future climate scenarios. By combining these observational and model-based approaches, we will improve the approach to projecting water resource change, and help to inform water management plans.

陆地上的生命依赖淡水。山脉起着水塔的作用，通过提升潮湿的空气来产生水，并提供临时的地面和地下储水，以便稍后释放到河流中。这些商店在经历季节性干旱的地区尤其重要，因为冰雪融化可以抵消干旱期间降雨量减少的影响。有两个主要的天然冻水储存库。雪是一种短期储存，在每天到季节性的时间尺度上，会推迟降雪后水分的释放。冰川融化还会季节性地释放水分。然而，冰川冰是一个更长期的蓄水池，可以储存数十年到数百年的水。在山区集水区未结冰的部分也可以观察到类似的行为。湿地、池塘和浅层地下水流等蓄积物提供短期储存，而湖泊和更深的地下水表现出长期释放特征。这些不同过程的组合决定了山脉对周围地区的水塔功能的大小和行为。这一点在安第斯山脉尤为重要，那里有一些全球最重要的水塔。安第斯山脉附近地区的人口依赖山区水资源饮用、粮食生产和水电，动植物也是如此。不幸的是，人类引起的气候变化正在改变安第斯水塔中储存的水。温室气体排放意味着，带雪的天气条件变得越来越不常见，耗尽了山上储存的雪。补充降雪的缺乏和气温的上升，正在导致冰川失去它们储存的冰，退回到山脉更高、更冷的地方。再加上气候变化对流域其他地区的影响，这导致了安第斯山脉的水资源短缺。持续的干旱正在冲击人口稠密的城市，那里的人口集中增加了对水的需求。例如，利马和瓦拉兹(秘鲁)、拉巴斯(玻利维亚)和圣地亚哥(智利)等城市都位于冰雪融化促进河流流动的集水区。然而，上游农村地区对气候变化的适应能力较差，往往更直接地依赖冰雪融化。这影响了农业灌溉，强调了该地区的粮食安全。为了帮助管理水供应的这些变化，该项目旨在实现两件事。首先是提供更好的监控。安第斯山脉海拔很高，仪器设备很差。为了弄清条件在哪里变化以及变化的速度，我们将安装更多的科学仪器来测量降雪、天气和河流流量。为了将我们现在可以测量到的变化与背景联系起来，我们需要更长的观测记录来追溯到过去。自1850年以来，许多冰川一直在消退，在我们将要绘制的地貌上留下了印记。利用卫星图像，我们可以追踪这些冰川从20世纪70年代到现在的消退过程。我们还将利用过去气候条件的记录，由水手在船舶航海日志中记录，并以沉积物形式存储在景观中。我们的第二个目标是预测未来的变化，这需要气候、冰川和河流过程的计算机模型。政策制定者需要这样的预测，他们需要可靠地了解未来可能发生的变化。我们将结合最先进的模型，模拟安第斯山脉十个流域的水资源变化。为了评估我们的模型做出预测的技能，我们将根据我们对过去条件和当前变化的观察对它们进行测试。在复制观测条件方面表现良好的模型将被用来预测一系列未来可能的气候情景。通过将这些观测方法和基于模型的方法相结合，我们将改进预测水资源变化的方法，并帮助为水资源管理计划提供信息。