Groundwater is a finite resource under continuous external pressures. Current unsustainable groundwater use threatens the resilience of aquifer systems and their ability to provide a long-term water source. Groundwater storage is considered to be a factor of groundwater resilience, although the extent to which resilience can be maintained has yet to be explored in depth. In this study, we assess the limit of groundwater resilience in the world's largest groundwater systems with remote sensing observations.

Groundwater is an increasingly important water supply source globally. Understanding the amount of groundwater used versus the volume available is crucial to evaluate future water availability. We present a groundwater stress assessment to quantify the relationship between groundwater use and availability in the world's 37 largest aquifer systems. We quantify stress according to a ratio of groundwater use to availability, which we call the Renewable Groundwater Stress ratio.

This paper briefly reviews the history of Reusable Launch Vehicle development and recommended reuse techniques based on the lessons learned from those efforts. The paper considers a range of techniques for recovery and reuse of launch vehicles. Launch vehicle component cost and weight by major element are also discussed as a method of determining cost/benefit of reuse. Of particular interest are non-propulsive approaches as economic alternatives to propulsive approaches.