Bedmap Himalayas - Reconnaissance

在喜马拉雅山脉的高处，成千上万的冰川缓慢地向山下流动，在季风和冬季降雪的作用下，上游的冰川在冰川口的温暖温度下融化，以融水的形式流入亚洲的主要河流——恒河、印度河和雅鲁藏布江。如果降雪量与融雪量相等，冰川的大小就会保持不变，但在干旱的几个月里，融水的稳定径流保持了河流的流动。在干旱期间，当季风降雨和降雪失败时，融化继续，在炎热的天气里，它会增加，在最需要的时候为下面的平原提供水。这些水被大约8亿人用于饮用、灌溉农业、水力发电和工业。在印度河流域，有2.37亿人在旱季严重依赖冰川径流灌溉，而这一人口正以每年400万的速度增长。与此同时，从2003年到2009年，由于降雪跟不上融化的速度，喜马拉雅山每年损失约26立方公里的冰。对于一些河流流域的居民来说，冰川径流是一种至关重要的资源，但由于从未对其进行过调查，人们对其数量知之甚少。据报道，在20,000到40,000个冰川中，只有不到10个有直接的厚度测量，而通过间接方法（如从表面面积估计）估计的体积在1670到6500立方公里之间。这种不确定性使得很难预测这种脆弱但非常宝贵的水资源的未来。由于几个原因，测量冰川体积并不容易。我们可以使用像x射线系统一样的雷达，透过冰川看到它们的床，测量它们的厚度，但在喜马拉雅山脉，许多冰川都被一层从周围陡峭的山壁上掉下来的碎石覆盖着。这个屏幕上的石头大约是用于极地冰调查的雷达波长的大小，所以它们散射雷达信号，而不是让它穿过冰。此外，融化的冰川舌中的水吸收雷达能量，阻止它到达床。即使我们有一个合适的雷达可以看穿这些冰川，要到达它们也是很困难的，因为山脉非常崎岖，而且经常位于两国有争议的边界上。在这个项目中，我们将与加德满都国际山地综合发展中心（ICIMOD）的当地专家合作，将低频雷达系统带到一个覆盖着屏幕的尼泊尔冰川上，通过改变频率和功率，研究如何在这些具有挑战性的条件下看到冰川床。有了这些知识，我们将来可以为小型飞机设计一种雷达，可以快速方便地测量大面积。我们还将与ICIMOD的水文学家、冰川学家、地理学家和区域专家合作，为喜马拉雅地区设计一项空中调查，在最大限度地扩大冰川覆盖范围的同时，将飞行成本降至最低，提供区域冰分布的良好样本，优先考虑最依赖径流的河流集水区，并尊重边界和政治敏感地区。这可能会跨越尼泊尔、印度、巴基斯坦、中国和不丹的冰川地区。为了能够进行大规模的调查，我们必须与这些国家的科学家和政府机构建立合作关系。我们将通过在加德满都和在巴基斯坦伊斯兰堡的另一个ICIMOD办事处的访问接触，开始培养这些合作。与物流专家一起，我们还计划选择并参观一个山地飞机跑道，以检查它是否适合用作该地区冰川航空调查的物流枢纽。总之，这些活动将为我们进一步了解亿万人民赖以生存的水资源铺平道路。

High in the Himalayan mountains thousands of glaciers flow slowly downhill, fed in the upper reaches by monsoon and winter snowfall while melting away in the warmer temperatures at the glacier snouts, to flow as meltwater down into Asia's major rivers -the Ganges, Indus and Brahmaputra. If snowfall equals melt the glaciers remain the same size, but the steady runoff of meltwater through the dry months keeps the rivers flowing. During droughts when the monsoon rains and snowfall fail, the melt continues, and in hot weather it increases, supplying water to the plains below when it is most needed.This water is used by around 800 million people for drinking, irrigated agriculture, hydropower and industry. In the Indus catchment, 237 million people are rated as heavily dependent on glacier runoff for irrigation in the dry season, and this population is growing by 4 million per year. Meanwhile, from years 2003-2009, the Himalayas lost around 26 cubic kilometres of ice per year as snowfall has not kept up with melt. For the populations of some river basins, glacier runoff is a vital resource, but its volume is remarkably poorly known because it has never been surveyed. Reportedly fewer than ten of the 20,000 to 40,000 glaciers have direct thickness measurements, and volume estimates from indirect methods (like estimating it from the surface area) range from 1670 to 6500 cubic kilometres. This uncertainty makes it difficult to predict the future of this vulnerable but highly valuable water resource.It is not easy to measure the glacier volume for several reasons. We can use radar like an x-ray system to see through glaciers to their beds and measure their thickness, but in the Himalayas, many glaciers are covered in a layer of scree that has fallen from the steep walls of the surrounding mountains. The stones in this scree are about the size of the radar wavelengths usually used for ice surveys in polar regions, so they scatter the radar signal rather than letting it pass through into the ice. Also, water in the melting glacier tongues absorbs the radar energy, preventing it from reaching the bed. Even if we have a suitable radar that could see through these glaciers, just getting to them is difficult because the mountain ranges are extremely rugged and often lie along national borders that are disputed by the countries on either side.In this project, we will work with local experts from the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu to take a low-frequency radar system to a scree-covered Nepali glacier and, by varying the frequency and power, work out how to see the glacier bed even in these challenging conditions. With this knowledge, we can in future design a radar for a small aircraft that can survey large areas quickly and easily. We will also work with ICIMOD's hydrologists, glaciologists, geographers and regional experts to design an airborne survey for the Himalayan region that maximises glacier coverage while minimising flying costs, giving a good sample of the regional ice distribution, prioritising the most runoff-dependent river catchments and respecting boundaries and politically sensitive regions. This will likely span the glaciated areas of Nepal, India, Pakistan, China and Bhutan. To be allowed to conduct a large-scale survey, it is vital that we establish collaborations with scientists and government agencies in these countries. We will begin to cultivate these collaborations through visiting contacts in Kathmandu and another ICIMOD office in Islamabad, Pakistan. With a logistics expert, we also plan to select and visit a mountain airstrip to check whether it is suitable for use as a logistics hub for an airborne survey of the region's glaciers. Together, these activities will pave the way for a major advance in our understanding of a water resource relied upon by hundreds of millions of people.