Estimates of water demand in the Middle Illinois Water Supply Planning Region (WSPR) were developed for the period 2010 to 2060. The estimates were developed separately for five major water demand sectors: (1) public supply; (2) self-supplied domestic; (3) self-supplied thermoelectric power generation; (4) self-supplied industrial and commercial; and (5) self-supplied irrigation, livestock, and environmental. Estimates were developed for all sectors on a county level and for public supply at a facility level for 24 dominant public systems, including the largest systems in each county. The techniques used to develop estimates differed by sector and included unit-demand methods and multiple regressions. These methods provided estimates of future demand as a function of demand drivers and explanatory variables for many sectors and subsectors. Explanatory variables are those that influence unit rates of water demand, such as summer-season temperature and precipitation, median household income, marginal price of water, employment-to-population ratio, labor productivity, and precipitation deficits during the irrigation season. For most sectors and subsectors, total demand was estimated by multiplying unit rates of water demand by demand drivers. Demand drivers included such measures as population served by public systems, population served by domestic wells, number of employees, gross thermoelectric power generation, irrigated cropland acreage, irrigated golf course acreage, and head counts of various livestock types. For each sector, three scenarios were developed of future water demand that reflect different sets of plausible socioeconomic and weather conditions. These include a less resource intensive (LRI) scenario, a current trends (CT) (or baseline) scenario, and a more resource intensive (MRI) scenario. A “normal” climate, based on 1981-2010 climate “normals,” was assumed in all scenarios. Although the estimates suggest a plausible range of future demands, they do not represent forecasts or predictions nor indicate upper and lower bounds of future water demand. Different assumptions or different future conditions could result in predicted or actual water demands that are outside of this range.Total water demand in the Middle Illinois WSPR was an estimated 866 million gallons per day (Mgd) in 2010. Demand for self-supplied water for thermoelectric power generation dominates water demand in the region, making up 76 percent of the total water usage, or about 655 Mgd. Water for thermoelectric power generation is used almost entirely for cooling and generally returned to the source water body from which it was withdrawn, and thus is considered to be mainly non-consumptive. The consumptive loss, mainly in the form of evaporation, was an estimated 77 Mgd in 2010, or about 12 percent of the total. The CT and MRI scenarios assumedthat regional gross thermoelectric power generation remains constant from 2010 to 2060, with no change in water demand. The LRI scenario assumed that a single 136-megawatt (MW) generator at the E.D. Edwards power plant was retired in 2015, reducing the regional water demand to 588 Mgd.Self-supplied industrial-commercial was the next most important water demand sector in the Middle Illinois WSPR, with a demand of 150 Mgd in 2010, with Peoria County accounting for about 85 percent of this demand. The next most important demand sector was public water systems, at 46 Mgd in 2010, with Peoria County accounting for about 52 percent. The two remaining sectors, domestic and irrigation, livestock, and environmental combined accounted for 14 Mgd in 2010, or less than 2 percent of the total demand in the region.From 2010 to 2060, total demand in the region, not considering thermoelectric power generation, is estimated to increase by 241 Mgd under the LRI scenario, 320 Mgd under the CT scenario, and 425 Mgd under the MRI scenario. Most of the increase in total demand under all scenarios, particularly the CT and MRI scenarios, is accounted for by increases in self-supplied industrial-commercial demand. Sector totals for the thermoelectric power generation and industrial commercial sectors are subject to revision, specifically, the simulation of new power plants and water-intensive industrial facilities as well as the retirement of existing facilities.Three climate change scenarios, ranging from hot/dry to warm/wet, were analyzed to determine the impact that increasing temperature and changing precipitation patterns could have on water demands. Public water system demands were calculated to increase between 6.1 and 9.1 percent because of climate change, and increases in domestic demands were similar. Irrigation demands varied from a decrease of 11.5 percent in a wetter future environment to an increase of 1.3 percent in a drier environment. The impact of periodic droughts was also examined. For a severe drought, public water system demand was calculated to increase by 12.4 percent and cropland irrigation demand by 36.6 percent. Demands would return to normal once the drought ended.Illinois Department of Natural Resourcespublished or submitted for publicationis peer reviewedOpe
