The structure and dynamics of groundwater systems in northwestern India under past, present and future climates

印度是世界上最大的地下水农业用户。在过去40年里，从大规模地表水管理到广泛抽取地下水的革命性转变，特别是在西北部的旁遮普、哈里亚纳邦和拉贾斯坦邦。因此，印度西北部现在是地下水枯竭的热点地区，“地球上任何规模相当的地区地下水流失率最高”（Tiwari等人，2009年）。随着人口和工业化的迅速发展，对地下水的需求不断增加，加上气候变化对水循环的潜在影响，这种不可持续的地下水使用变得更加具有挑战性。有一些创新的社会经济战略可以解决这个问题，包括加强补给和地下水储存，但其实施和成功取决于区域对含水层系统的地质和水文地质以及地下水流动和补给的模式和速率的扎实了解。我们对区域地下水资源的了解主要来自基于卫星数据的低分辨率研究，或者来自当地调查;没有对地下水系统进行大规模的跨州综合研究。印度西北部的地下水被认为主要存在于埋藏的桑迪河道中，这些河道从喜马拉雅山脉向西南延伸，并被细粒泥隔开。只有少数通道在地表可见;大多数被掩埋，必须推断它们的存在。我们的方法是建立在这样的前提下，我们必须首先了解地质和几何含水层系统之前，我们可以希望估计它将响应于一组复杂的未来应力的方式。这意味着我们必须能够描述这些通道的位置、大小和特征，以及它们的年龄和三维模式。一旦确定了这些特征，我们就可以预测系统未来可能的行为。在本提案中，我们将首次提供印度西北部含水层系统的区域评估，沿着其在水循环变化和地下水使用方式下的演变模型。我们的项目将结合联合收割机在沉积学，地层学，沉积物路由和盆地演化，水文学和同位素地球化学的专业知识，以了解含水层系统的地质框架，其中的地下水的年龄，以及地下水位可能在未来50年内演变的方式。该提案的成果将包括：（1）覆盖印度西北部含水层系统的综合数据库，（2）更好地了解地下水的区域来源、年龄和流速，以及（3）一套关于地下水系统将如何的预测对一系列不同的未来情景做出反应。

India is the largest agricultural user of groundwater in the world. The last 40 years has seen a revolutionary shift from large-scale surface water management to widespread groundwater abstraction, particularly in the northwestern states of Punjab, Haryana and Rajasthan. As a result of this, northwestern India is now a hotspot of groundwater depletion, with 'the largest rate of groundwater loss in any comparable-sized region on Earth' (Tiwari et al., 2009). This unsustainable use of groundwater becomes even more challenging when set increasing demands from a burgeoning population and industrialisation, together with potential but poorly understood effects of climate-driven changes in the water cycle.There are a number of innovative socio-economic strategies that can address this issue, including enhanced recharge and subsurface water storage, but their implementation and success depend on solid regional understanding of the geology and hydrogeology of the aquifer systems, and of the patterns and rates of groundwater flow and recharge. What we know about regional groundwater resources comes largely from either low-resolution studies based on satellite data, or from local investigations; there has been no large-scale, cross-state integrated study of the groundwater system.Groundwater in northwestern India is thought to be largely hosted within buried, sandy former river channels, which extend from the Himalayas toward the southwest and are separated by fine-grained muds. Only a few channels are visible at the surface; most are buried and their existence must be inferred. Our approach is founded on the premise that we must first understand the geology and geometry of the aquifer system before we can hope to estimate the way it will respond to a complex set of future stresses. This means that we must be able to describe the locations, sizes, and characteristics of these channels as well as their age and three-dimensional pattern. Once these characteristics are determined, we can forecast the likely future behaviour of the system. In this proposal, we will provide, for the first time, a regional assessment of the aquifer system in northwestern India, along with models for its evolution under changes in the water cycle and in the way in which groundwater is used. Our project will combine expertise in sedimentology, stratigraphy, sediment routing and basin evolution, hydrology, and isotope geochemistry to understand the geological framework of the aquifer system, the ages of the groundwaters within it, and the ways in which groundwater levels are likely to evolve over the next 50 years. The outcomes of the proposal will include (1) a comprehensive data base that covers the northwestern Indian aquifer system, (2) much better understanding of regional sources, ages, and flow rates of groundwater, and (3) a suite of predictions for how the groundwater system will respond to a range of different future scenarios.