More than half of the world’s largest lakes and reservoirs are losing water — and climate change and human consumption are the main drivers, a new large-scale study warns.

Why it matters: About 2 billion people live in the basins of drying lakes, per the study published in the journal Science. Water insecurity is already an issue, with hundreds of millions of people around the world lacking reliable access to safe water.

• The findings underscore an urgent need to incorporate climate change and sedimentation impacts into sustainable water resources management, according to an editor’s summary accompanying the study.

Zoom in: Even with rains soaking the Hill Country, lakes Travis and Buchanan — Central Texas’ chief reservoirs — stubbornly remain only 51% full.

• With parched soils soaking up much of the rainfall, the amount of water actually flowing by creeks and rivers into the lakes last month was about 14.4% of the April historical median, per data dating to 1942.

What they’re saying: “The net volume loss in natural lakes is largely attributable to climate warming, increasing evaporative demand, and human water consumption, whereas sedimentation dominates storage losses in reservoirs,” per the study.

By the numbers: Capacity in Lake Buchanan, very much one of those human-made reservoirs, was 992,000 acre-feet upon its completion in the late 1930s.

• Today, after decades of dirt washing into waterways and settling on the lake bottom, its capacity is 880,356 acre-feet — an 11% drop in available volume.

Be smart: The Lower Colorado River Authority’s 2020 Water Management Plan for the lakes — essentially, the driving manual for operations of the Colorado River — doesn’t include the terms “climate change” or “global warming,” per an Axios review of the document, even though scientists warn of hotter, drier summers ahead.

• The LCRA is the nonprofit utility that doles out water from the lakes to more than a million Central Texans — and its board members are appointed by the governor.

• River authority officials have long said their decision–making is guided by historical data related to drought and water supply availability.

Zoom out: The team of international researchers looked at 250,000 lake-area satellite images taken from 1992 until 2020 to examine the area and water levels of 1,972 freshwater bodies.

What they found: 53% of lakes globally experienced a drop in water storage during that period — a water loss equivalent in volume to 17 Lake Meads, the largest reservoir in the U.S., according to the study.