Specific Connection in Energy-Water Nexus
Of all U.S. business sectors, agriculture is the largest consumer of both electricity and water. Most of the electricity used by agriculture goes to pump groundwater at a cost of almost $1.2 billion each year. This combined electricity and water use is concentrated in California and other Western United States, with California farmers using 20 percent of the total U.S. agricultural electricity, or about 10,000 gigawatt-hours (GWH) per year.
The agricultural demand for electricity, which is driven by the scarcity of water, is expected to grow rapidly, because supplies of surface water are scarce and competition for those supplies is growing.
Resource Quantities
Among the factors that drive water scarcity and demand for agricultural electricity is the growing competition for water from environmental and urban interests. Another factor is climate warming, which already is changing stream flow patterns in ways that limit supplies during summer, the period of highest agricultural water demand.
Thus several factors are driving the increases in agricultural electricity use. The link between water scarcity and agricultural electricity use can be illustrated with two examples—drip irrigation and intensive, intentional groundwater storage. Farmers throughout the West are switching to pressurized irrigation systems to conserve water. In California alone, pressurized irrigation methods, such as drip irrigation, now cover some 4.2 million acres. Such systems enable farmers to decrease their need for water, but at the cost of increased energy use. In California pressurized irrigation systems have resulted in a 2.3-GWH per-year increase in agricultural electricity use since the 1970s. At the same time, farmers are using groundwater storage more intensively than in the past—actively storing water below ground in wet years and withdrawing it during dry periods. Groundwater storage also has dramatically increased farmers’ need to pump groundwater.
Sector Challenges and WETT Solutions
The close link between water and energy demands in agriculture poses a special challenge in an era in which both are scarce and expensive. Many technical solutions to water scarcity, such as drip irrigation, increase energy use. Other technical solutions, including increased surface storage, pose risks to the environment. Scientists on the Water and Energy Technology Team (WETT) at Lawrence Berkeley National Laboratory are meeting this challenge, developing programs to increase the efficiency of water management and reduce energy demands. These programs focus on three areas of effort: forecasting climate trends and their impacts on agriculture, minimizing effects of farm drainage on the in-stream environment, and improving management of surface and groundwater storage.
WETT scientists are constructing a suite of climatic, hydrologic, and economic models designed to forecast climate trends and their effects on agricultural water and energy use. For example, our climate models indicate ways in which warming trends will change the timing of snowmelt and stream flows in many Western states. Linked hydrologic models forecast the effects that changing stream flow patterns will have on irrigation supplies and groundwater levels. This suite of climate-related models provides guidance for water managers seeking to protect the farm economy now and in the future. Finally, coupled agricultural-economic models help planners understand some of the effects of changing irrigation supplies on agricultural production, water, and electricity use.
Other WETT activities involve designing real-time scheduling programs to control irrigation drainage, coupled with detailed models of the capacity of rivers to assimilate that drainage. This effort is expected to enhance agricultural water supplies, minimizing the amount of additional water needed to protect in-stream quality, while reducing groundwater pumping and its associated energy costs. At the same time, our scientists are building complex models to track the movement of salinity and pollutants through aquifers in agricultural areas. These groundwater models help farmers both to predict the impact of intensive pumping and recharge programs on groundwater quality and to better manage those programs in order to preserve valuable aquifers.
Another area of research focuses on using mathematical simulation and optimization models to study a range of options for managing reservoirs. Reservoirs usually are operated to supply surface water and generate electricity, as well as to provide flood protection and recreational benefits. WETT scientists are building models of reservoir/aquifer systems in order to evaluate the relationship between reservoir operation and aquifer systems and to assess their impacts on total regional water and energy supplies. A key goal of our group is to better understand and manage the energy/water tradeoffs associated with water storage.
