One of the challenges we can expect to face in a climate-changed world is a dramatic redistribution of water resources. Some areas will experience drought, as California and all of the Southwest is currently facing, while others will be forced to deal with flooding, either from massive storms or snowmelt in the spring. These are enormous challenges which could threaten our economy and in some cases our livelihoods. The question of how we can prepare for this is an overwhelming one, though we know that we can surely benefit by becoming more resilient. In this context, this means, among other things, reducing the level of water consumption required for our way of life. That also implicitly means reducing our energy consumption, since the two are so inextricably linked.
There is some good news on that score. According to the US Geological Survey (USGS), water use in the US, in the year 2010 has fallen to the lowest level since before 1970. This was largely due to reductions in the two largest water consuming activities: thermoelectric power generation and agricultural irrigation. The biggest drop was in withdrawals for feeding and cooling thermal power plants, which accounts for about 45% of all water withdrawals. That number fell by 20%. This derived from a migration away from fossil fuel plants, particularly coal, as well as improved efficiency. Irrigation, which accounts for another 33% of all withdrawals, fell by 9%. Public water supply withdrawals also fell by 5% despite an increase in population. The only areas that saw increases were aquaculture and mining. What’s not clear is whether that trend will begin to reverse with severe droughts like the one currently underway in California, which has already reversed decades of progress in air quality improvement.
These numbers were rolled up at a national level. Drilling down into the numbers, as the folks at the Hamilton Project did, shows a wide variation in water usage and water availability across the various regions of the country. Just because the national average is down, deosn’t mean that some areas aren’t struggling.
Regionally, most of the withdrawals for power generation occurred east of the Mississippi, though there is a substantial concentration in Southern California as well. As for irrigation, on the other hand, most of this took place west of the Mississippi, though there is also a dense pocket in Southern Florida. Domestic withdrawals vary, on a per capita basis, from 51 gallons per day in Wisconsin, to 168 gallons per day in Idaho. These differences are mostly attributable to landscaping.
The folks at ACEEE are looking at opportunities for savings at the energy-water nexus. Their recent report Watts in a Drop of Water: Savings at the Water-Energy Nexus, looks at opportunities to save energy in the conveyance, treatment, distribution of water and well as the treatment and discharge of wastewater. Their research also found large disparities by location, due to the various approaches being used. For example, if a municipality received their water from an upland source that could be fed to them by gravity, made a huge difference in energy consumption compared to those with downhill sources that had to be pumped in. According to Scott Sklar of George Washington University, 18% of the eastern electric grid and 30% of the western grid is dedicated to moving water and sewage around. The report calls for mew metrics to highlight the amount of embedded energy in a given water flow.
There is a tremendous opportunity here to continue to improve the efficiency of our water and energy system that can be best addressed by the two utilities working together and taking a systems approach. The more efficient we can become, the more resilient we will be and the better positioned will we be to withstand the shocks that lie ahead.