November 28, 2018
Nexus: “A connection or series of connections between two things”
A nexus exists in the food, water supply and energy sectors. It takes water to make food and energy. Energy is needed secure, treat and distribute drinking water as well as collect and treat wastewater. And a good deal of energy goes into producing, processing and distributing food. These three sectors compete for the same water. Those sectors can also impact the quality of our natural resources in many ways.
In the water sector, energy is used primarily for pumping and distributing drinking water. A significant amount of energy is also used to mix, aerate and otherwise treat wastewater. Then there is also the energy required for maintenance of the process as well as the ‘embedded energy’ from construction and installation of treatment and distribution facilities. Just how much energy is used by a water utility is unique to each facility. Berryville, AR once had a source of water on top of a mountain south of town. The elevation was such that water flowed by the force of gravity down to town and throughout their distribution system. It was a spring source, so treatment was minimal. Their energy use at the time was also minimal. Most utilities on the other hand will need to pump raw untreated water from either a surface supply such as a lake or from an aquifer up to their treatment plant. Then they treat the water and pump it again to fill and pressurize their distribution system. Water is heavy. Moving and lifting water takes lots of energy. In fact, the United States Department of Energy estimated in 2006 that the water supply sector used between 3 ½ and 4% of all electrical energy produced in the US.
Roughly 80% of electrical energy in the US is mostly produced either through hydroelectric or thermoelectric processes. The remainder is produced by solar or wind energy processes. With the exception of solar panels, electricity is produced a generator. A force is required to turn the generator. In Hydroelectric power, the force is provided by moving water through a turbine that turns the generator. For thermoelectric power, coal, gas, nuclear or some other fuel is used to boil water creating steam that turns the turbine. In either case, a generous supply of water is needed. The greatest amount of water withdrawn from the environment is by the energy sector. However, most of that water is returned to the environment. Producing electricity is actually responsible for consuming about 3 ½ % of water consumed in the US each year according to the DOE. Crop irrigation is actually the largest consumer of water in the US.
From the above, it can be seen that agriculture is clearly a huge user of water. It is estimated that irrigation of crops accounts for roughly 80 % of water consumed in the US1. And that is not all of the water consumed. Water is also required to process, distribute and prepare food. Much of that processing and preparation water must be at least drinking water quality. Water use during producing, harvesting, transporting, processing etc. of food also are big energy consumers.
Clearly, the Three sectors; food, energy and water, are interconnected in many ways. It may not be as clear that these sectors also have conflicting interests. They all compete for the same water. Providing water for agriculture or energy, may take water away from water supply. Also, using water for water supply means that water is no longer available for energy or food production. And when water is used for energy production, it may no longer be available where needed for water supply or agriculture. As a local example, in Beaver Lake, Arkansas, both the Beaver Water District (BWD) and the Southwest Power Administration (SWPA) have allocations granted by the US Army Corps of Engineers (COE) to take water from the Lake. BWD takes water from the lake to supply NW Arkansas with domestic (drinking) water. SWPA uses water to produce hydroelectric power at Beaver Dam. They then distribute that power into the electric grid. Currently there is plenty of water and there is no conflict. But, some day in the future, if the region continues to grow, water production at BWD will reach the capacity of their allocation. At that point in time, BWD and the SWPA will have an inherent conflict. A prolonged drought may also cause a shortage of water potentially creating competing uses of the lake. Planning for use of the water in the lake then requires consideration of both sectors, i.e. the nexus. Now imagine that Beaver Lake was in a region where there was also a large demand for agricultural irrigation. The situation becomes complicated quickly.
So, what does all of this have to do with Forests and Drinking Water. First of all, the forestry sector is a big user of both energy and water. Back in 2006, the DOE found that pulp and paper processing, a portion of the forest sector, used 3.3% of electricity produced in the US. Roughly the same as the water sector. The amount of water required to process pulp and paper is difficult to determine. In 2002, K. Ravi used a value of 17,000 gallons per ton of pulp. That figure was not documented but is likely in the ball park. Ravi also reported that new equipment was coming on line that was more water efficient. So, let’s just say that producing pulp takes a lot of water. Water is of course used in other aspects of the forestry industry as well. Secondly, forested watersheds provide a reliable, high quality source of water for drinking water production. A nexus exists.
The Food, Water, Energy (and Forestry?) nexus is neither good nor bad. It’s existence merely indicates the need for coordination in planning among the sectors for use of the common resources. Organizations like the Arkansas Forests and Drinking Water Collaborative provide a forum where divers agencies and organizations can meet to discuss issues such as the nexus. Communication is the first step toward effective co-management.
1. US Department of Energy. 2006. Energy demands on water resources, report to congress on interdependency of Energy and Water
2. Ravi, K. 2002. Pulp and paper industry: water use and wastewater treatment trends. Frost and Sullivan Insite Report