想象一下，您是印度西北部拉贾斯坦邦的小麦农民。小麦需要的水比降雨更多，尤其是在干旱季节。因此，您要钻井。

您不必为使用的水或为泵提供动力的电费，因此让泵运行。虽然您知道水来自脚下某个地方的含水层，但它是看不见的，散布在土壤和岩石层中。因此，排干含水层与排水储层大不相同，在那里您可以看到水位下降。

You and your neighbors, and other farms, companies and cities around the world, keep withdrawing water from these underground sources with little regard for how much water they use and how much is left. People have an incentive – and no disincentive – to tap as much groundwater as they can. The result is a race to the bottom of the aquifer.

这种非常本地现象的结果是通过研究在全球范围内捕获的上周发布by NASA and the University of California, Irvine. The Gravity Recovery and Climate Experiment (GRACE）卫星表明世界上许多最大的含水层are being depleted at a much faster rate than they can be replenished, from the Middle East, India, North Africa and Central Asia to California’s Central Valley.

这些数据和分析至关重要，提高了人们对不足的问题和迫在眉睫的危机的认识，并允许政府，发展组织，公司和研究人员将其地下水工作集中在最糟糕的地区。

但是，还有更多的工作要做。这激发了WRI的水团队专注于其他关键背景因素：地表水竞争，地下水枯竭的综合效果，以及我们对地下水资源本身的全面了解，从当前的地下水位水平到可持续的撤离率等等。

Dry Surface? Look Out Below

供求都必须是有关减少水资源减少的任何讨论的一部分。宽限期确定的所有关键区域在地表河流和溪流中面对高到极高的水应力。在高度水压力的地区，每年企业，农民，居民和其他消费者都会撤出40％至100％的当地供水。Wri的Aqueduct Water Risk Atlas地图世界各地的水压力。中东以深红色和灰色的被子出现在地图集中，表明用户每年每年撤回80％或更多可用的可续签地表水，这表明用户压力很高。

更远的东部，印度的水压力显示出与恩典的地下水位下降地图相似的模式。一大批极高的地表水应力覆盖了印度西北部。由于地表水有限，该地区的农民正在撤出地下水也就不足为奇了。更快速than anywhere else on Earth, making the water situation even more precarious. Across the country, 54 percent of 4,000 measured groundwater wells are declining.

加利福尼亚州的中央山谷是另一个高效的农业地区，在宽限期分析中为地下水耗尽了危险。WRI绘制了加利福尼亚州灌溉农业土地上自然存在的地表水的竞争，地表水应力再次反映了高地下水压力的区域。关于66％of the state’s irrigated agriculture faces extremely high levels of baseline water stress. It’s long been known that Central Valley groundwater is being pumped at unsustainable rates. In the midst of California’s current epic drought, with no natural replenishment of aquifers and over-pumping, groundwater tables are declining alarmingly.

Improving Global Groundwater Estimates

As valuable as GRACE’s groundwater data is, it has a crucial gap: it cannot show the total volume of groundwater available in the aquifers it tracks, only the rate of decline. Without knowing when the aquifers will go dry, or when water tables will sink so low that they are effectively inaccessible, users and water managers are blind to the scope and severity of their problems.

含水层中存储的水数量的全球数据集将是无价的，但是还有很多年。在WRI，我们正在计划为渡槽水风险地图集的新全球地下水数据层作为第一步。与合作乌得勒支大学在荷兰和三角洲，这是一个荷兰水研究组织，我们正在准备更详细的地下水模型。我们将为世界各地的地下水水平和提取率创建全面的高分辨率地下水风险图。我们还计划一个地下应力图，以说明每年给定含水层中充电与耗尽的比率。

Groundwater is a valuable resource the world over. Managed sustainably, it can support food production and growing cities and businesses. But truly understanding the nature of this critical resource, how much groundwater there is, how long it may last in different places at current rates of extraction, and what sustainable recharge rates are, is essential for many countries’ future economic development.