Water is a critical resource, but ensuring it is available faces challenges from climate extremes and human intervention. In this Review, we evaluate the current and historical evolution of water resources, considering surface water and groundwater as a single, interconnected resource. Gravity Recovery And Climate Experiment (GRACE) satellite data show declining, stable, and rising trends in total water storage over the past two decades in various regions globally. Groundwater monitoring provide longer term context over the past century, showing rising water storage in Northwest India, Central Pakistan, and Northwest United States and declining water storage in the US High Plains and Central Valley. Climate variability causes some changes in water storage but human intervention, particularly irrigation, is a major driver. Waterresource resilience can be increased by diversifying management strategies. These approaches include green solutions, such as forest and wetland preservation, and gray solutions, including increasing supplies (desalination, wastewater reuse), enhancing storage in surface reservoirs and depleted aquifers, and transporting water. A diverse portfolio of these solutions, in tandem with managing groundwater and surface water as a single resource, can address human and ecosystem needs while building a resilient water system.Water is a critical resource, but ensuring it is available faces challenges from climate extremes and human intervention. In this Review, we evaluate the current and historical evolution of water resources, considering surface water and groundwater as a single, interconnected resource. Total water storage trends varied among regions over the past century. Some areas, including Northwest India, Central Pakistan, and Northwest United States, have seen rises in water storage over the past century. Others, including the US High Plains and Central Valley, have experienced net declines. Climate variability causes some changes in water storage but human intervention, particularly irrigation, is a major driver. Waterresource resilience can be increased by diversifying management strategies. These approaches include green solutions, such as forest and wetland preservation, and gray solutions, including increasing supplies (desalination, wastewater reuse), enhancing storage in surface reservoirs and depleted aquifers, and transporting water. A diverse portfolio of these solutions, in tandem with managing groundwater and surface water as a single resource, can address human and ecosystem needs while building a resilient water system.