Water
Managing Water Flows at Civilizational Scale
A constant supply of water and power, paid for downstream.
Dams store water through dry seasons and generate hydroelectric power, and diversions carry that water to cities and farms. The costs fall on the river below the dam and on the people and ecosystems that depend on it.
Disrupted fish migration, lost wetlands, altered sediment transport, changed river temperatures, and diminished downstream flows.
Upstream dams and diversions have so reduced its flow that it no longer consistently reaches the Gulf of California.
1 Veldkamp, T. I. E., et al. (2017). Water scarcity hotspots travel downstream due to human interventions in the 20th and 21st century. Nature Communications, 8, 15697. Colorado River: U.S. Bureau of Reclamation, Colorado River Basin Water Supply and Demand Study (2012).
Where Pollution Comes From
Regulation is easiest when you can point to the pipe.
Contaminants from a clearly identifiable conduit, such as a pipe, ditch, channel, or well. The source is known, so it can be permitted and monitored.
Pollutants from broad, diffuse places: agricultural, residential, and industrial activities across a whole watershed.
Loose soil swept into waterways makes the water turbid (cloudy) and reduces light penetration.
Chemicals from agriculture, energy, and infrastructure (as in Flint); bacterial and viral contamination, including feedlot runoff.
Sources: U.S. EPA, Basic Information about Nonpoint Source (NPS) Pollution and NPDES Permit Basics; USGS Water Science School, Turbidity and Water.
Water Scarcity and Conservation
The UN's goal of water security means reliable access to safe, affordable water for everyone.
- In sub-Saharan Africa, fewer than half of people have safely managed drinking water; hauling it falls mostly on women and girls.
- In California's 2015 drought, the governor ordered a 25% statewide cut in potable urban water use, compared with 2013.
- Cape Town planned public collection points for a 2018 “Day Zero” that never came, because residents cut use sharply; wealthier homes added tanks and boreholes.
- Some Middle Eastern nations without adequate fresh water have invested heavily in desalination.
WHO/UNICEF JMP (2025), Progress on Household Drinking Water, Sanitation and Hygiene 2000–2024; California EO B-29-15 (2015); City of Cape Town, Water Outlook 2018. Photo: Paul Jeffrey/Alamy Stock Photo, via W. W. Norton.
Where Do We Use the Most Water?
- Water budget: comparing all the water inputs and outputs.
- But which sectors (farms, cities, homes, industry) actually withdraw the most? Your intuition may surprise you.
Map: U.S. Drought Monitor, May 31, 2022 (National Drought Mitigation Center, USDA, NOAA), as reproduced in Sherman & Montgomery (2023), W. W. Norton.
Garbage, Fossil-Fuel Pollution, and Runoff
Human activity harms the ocean in three big ways: plastic garbage that breaks into microplastics, which can carry and release harmful chemicals; fossil-fuel pollution from spills and airborne mercury; and agricultural runoff that creates oxygen-starved “dead zones.”
NOAA Marine Debris Program, Microplastics; NOAA, Gulf of Mexico Dead Zone. Table 7.1 from Sherman & Montgomery (2023), W. W. Norton; photos: Olenalavrova/Shutterstock, Design Pics/Jeff Schultz/Newscom, NASA.
Overfishing, Climate Change, and Acidification
Three more pressures push ocean ecosystems toward collapse: overfishing faster than stocks can recover, a warming climate that disrupts food webs, and acidification. As the ocean absorbs CO₂, its pH falls and carbonate ions grow scarcer, so shell-building animals struggle to build and keep their calcium carbonate shells.
NOAA Pacific Marine Environmental Laboratory, What Is Ocean Acidification?; FAO (2018), The State of World Fisheries and Aquaculture. Table 7.1 from Sherman & Montgomery (2023), W. W. Norton; photos: Ihi/Shutterstock, Alexander Semenov/Science Source, Jean-Paul Ferrero/Pantheon/Superstock.
Protecting Fresh and Salt Water
ASU’s Global Futures Water Institute is “dedicated to forecasting and tackling water challenges at all scales, from local communities to national systems.” In the desert Southwest, individual choices add up. Here’s where to start.
- Know your water: find where your water comes from and what’s in it via the EPA’s Consumer Confidence Report (CCR) for your provider.
- Rethink your yard: replace thirsty grass with desert-adapted (xeriscape) landscaping. An ASU study with the City of Phoenix modeled park turf irrigation and found that shallower, better-timed watering could cut the water applied by 15–30%.
- Cut indoor use: shorter showers, turn off the tap while brushing, run full loads, and install EPA WaterSense fixtures. Fixing easily corrected leaks saves about 10% on a typical water bill.
- Push for bigger change: ask college or city administrators about irrigation timing, low-water plants, and recycled water. Institutional changes scale fastest.
- Learn & advocate: follow the Kyl Center for Water Policy’s Arizona Water Blueprint. Arizona’s total water use has held below its 1957 level while the population grew several-fold, largely because irrigated farmland was converted to cities, alongside conservation.