Since water keeps flowing, you may not be used to considering it as a limited, finite resource. However, at any given time there's only so much usable fresh water available for core needs such as drinking, sanitation, agriculture, energy production, ecosystem health, and industrial and commercial uses.
One of the most influential concepts in managing nonrenewable resources has been "peak oil" — which describes the point when the cost to extract, process, and transport the resource starts to rival or outweigh the benefits. This concept also can be applied, with some adaptation, to water management and use.
Viewing local, regional, national, and global water issues through the lens of "peak water" can yield some interesting angles on water-related stories and long-term water issues.
The peak water concept was explained in a paper published in May  by the Pacific Institute.
- Pacific Inst. press contact: Nancy Ross,  510-251-1600 x 106.
- Pacific Inst. director Peter Gleick gave a talk  earlier this year explaining peak water, and outlining possible ways to use this concept to enhance water management.
Gleick describes three main types of peak water:
- Peak renewable water: Surface flow constraints limit total water availability over time. (Such as the Colorado River — all water is used before the river reaches the ocean.)
- Peak nonrenewable water: Production rates substantially exceed natural recharge rates or where overpumping or contamination leads to a peak production followed by a decline. (Such as groundwater from the Ogallala Aquifer in the US Great Plains, which has long been drained beyond recharge rates for agricultural use.)
- Peak ecological water: The point beyond which the total costs of ecological disruptions and damages exceed the total value provided by human use of that water. (Such as the Aral Sea in Central Asia.)
To apply these concepts to local, state, regional, national, or global issues, you'll need data:
- USGS water resources.  Includes the National Water Information System,  the definitive resource for current and historical data on US surface water, groundwater, and water quality.
- EPA Surf Your Watershed.  Searchable databases of US watershed information, with context about water contamination and local citizen groups.
These resources also explain the sources of local fresh water, their annual capacity, and estimates of water usage.
In your coverage of potential local or regional impacts of climate change, ask how climate change may affect the quality and quantity of local surface water and groundwater. This is also a factor to consider in coverage of growing sources of water pollution such as surface runoff and hydraulic fracturing for natural gas extraction.
Fossil fuel-powered electricity generating plants require enormous amounts of fresh water to operate. How might projected patterns in electric demand, and integration of renewable power generation, affect electricity-related water demands? For instance, solar thermal power generation (where solar heat is used to create steam to drive turbines) requires significant water usage, while photovoltaic generation does not require water (although it generates less power). Viewed through the peak water lens, solar thermal plants in sunshine-rich but water-poor environments like the southwestern US might have difficult long-term environmental economics.
The weblog Peakwater.org  offers leads on peak water-related news around the US and world.
Check with water utilities, water management authorities, agricultural agencies and extension offices, and environmental regulators about their views on peak water, and how this concept might affect long-range water management planning or policy.