Global water resources and the role of groundwater in a resilient water future

Abstract

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.

Complex Policy Mixes are Needed to Cope with Agricultural Water Demands Under Climate Change

“…Far from being a solution in decline, more than 70 water transfer megaprojects (i.e., those with construction costs ≥ US$1 billion, distances ≥ 190 km and volumes ≥ 0.23 km 3 yr − 1 ) are expected to be built (many of them to supply water to large irrigation projects) worldwide (Shumilova et al 2018). Projected transfer volumes for planned or proposed projects (1,910 km 3 per year ) are an order of magnitude greater than existing projects, with a total transfer distance of more than twice the length of the Earth's equator (Shumilova et al 2018;Scanlon et al 2023).…”

“…Currently 2 billion people depend on groundwater (Famiglietti 2014) as their primary source of drinking water, and groundwater supplies around half of the world's irrigation surface (Siebert et al 2010). Globally, it is estimated that one-quarter (585 km 3 yr − 1 ) of the total water withdrawals are drawn from groundwater (Scanlon et al 2023). As a consequence, immense reservoirs that seemed inexhaustible are experiencing rapid depletion rates (Famiglietti 2014;Bierkens and Wada 2019;Jasechko and Perrone 2021;Scanlon et al 2023).…”

“…Globally, it is estimated that one-quarter (585 km 3 yr − 1 ) of the total water withdrawals are drawn from groundwater (Scanlon et al 2023). As a consequence, immense reservoirs that seemed inexhaustible are experiencing rapid depletion rates (Famiglietti 2014;Bierkens and Wada 2019;Jasechko and Perrone 2021;Scanlon et al 2023).…”

Data space inversion for efficient uncertainty quantification using an integrated surface and subsurface hydrologic model

“…We now discuss application of the DSI methodology in a synthetic alluvial stream-aquifer context. Alluvial river systems come from surface water capture (Scanlon et al, 2023). They provide productive aquifer systems and natural riparian filtration; see, for example, Epting et al (2022).…”

Measuring water from space

“…A remarkable innovation at the time, GRACE's measurements revealed changes in sea level, soil moisture, and ice sheets. In more than 15 years of operations, GRACE flew around Earth to measure changes in distance between the two satellites in response to gravity, providing new insights into changes in large-scale terrestrial water storage (TWS) under the warming climate 4,5 .…”