Water Demand Analysis
The United States Geological Survey (USGS) publishes county level water use estimates every five years categorizing water usage by land use. LEAM simulations project changes in total acreage for each land use type, which can be combined with the USGS data to predict future water demand. In this analysis, water consumption rates were based on the USGS consumption data, the only adjustment needed being for new homes, which are required to meet the provisions of the Energy Policy Act of 1992 for water-consuming fixtures. Therefore, residential water demand was adjusted downward by 28 gallons per day, per capita to account new homes. Population projections from the Regional Economics Applications Laboratory (REAL) at the University of Illinois were used to estimate the number of households based on population change and the projected average household size in the region during the project timeframe. Total water demand was broken down into three categories, residential, commercial, and agricultural, defined as follows:
Residential water demand is calculated by dividing the sum of Domestic and Public supply water by the number of households.
Commercial water demand is calculated by a two-step process: 1. Convert the commercial acreage into building square footage via a conversion factor (in this case 13,126); 2. Divide the sum of Industrial and Public supply<!--[if !supportFootnotes]--> water by the total square footage from Step 1.
Agricultural water demand is calculated by summing the Irrigation and Livestock water and dividing by Agriculture acreage.
The following diagram captures some of the connections between land-use change and water stock in a region. Water extraction is divided into several sectors including public supply, domestic, industrial, and agricultural water use. The figure shows how water demand is related to land use change factors such as changes in household units, commercial/industrial buildings, and agricultural land.
Figure 1: Water demand model
The 2000 USGS Estimated Water Use Report used as a base for the model provides county level water use statistics by category (DuPage County water is purchased from the Chicago Department of Water Management and withdrawn from Lake Michigan, so the data for DuPage County was collected from the county itself). These categories include:
Domestic Water: Self supplied water used for all indoor household purposes as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens.
Industrial Water: Water used for fabrication, processing, washing, and cooling, and includes such industries as chemical and related products, food, mining, paper and allied products, petroleum refining, and steel.
Irrigation Water: Water that is applied by an irrigation system to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands such as parks and golf courses. Irrigation includes water that is applied for pre-irrigation, frost protection, chemical application, weed control, field preparation, crop cooling, harvesting, dust suppression, the leaching of salts from the root zone, and water lost in conveyance.
Public-Supply Water: Water withdrawn by public and private water suppliers that furnish water to at least 25 people or have a minimum of 15 connections. Public suppliers provide water for a variety of uses, such as domestic, commercial, industrial, thermoelectric power, and public water use.
Livestock Water: Water for livestock watering, feedlots, dairy operations, and other on-farm needs. Types of livestock include dairy cows and heifers, beef cattle and calves, sheep and lambs, goats, hogs and pigs, horses and poultry.
Click on the links below for spatial water demand results by scenario type.
Regional totals by demand sector
County by county water use data from 2000 was gathered and entered into the water demand model. Results for the total demand by county as well as for each of the three sub-categories by county are shown in figures 2-5. It is important to consider the difference in scale of the different demand sectors; residential demand is always the largest by far.
Figure 2: Total regional water demand change from 2001 to 2030 across scenarios.
There is a total decrease in water demand in Cook County during the projection period due to a loss of residential uses to commercial redevelopment. Across simulations, residential development is occurring outside of Cook County to a greater degree. Because residential demand is the most significant contributor to water usage, a reduction in residential uses and therefore residential water demand, will create a net reduction across the county.
Figure 3: Reduction in residential water use across townships.
It is important to note that the increases in demand projected for residential and commercial uses, those uses that agricultural land will be converted to, far exceed any reduction of agricultural demand. In fact, residential increases in demand alone will exceed reduction in agricultural demand by a factor of 2500, in Will County. This dramatic shift in water demand illustrates the need for responsible resource management and planning. Developing guidelines for encouraging aquifer recharge through site design and directing development away from recharge zones can help reduce the impact of land conversion from agricultural to other uses.
Figure 4: Change in commercial water use across scenarios.
As was expected given the behavior of the various demand sectors, commercial water demand across each of the townships remains relatively flat. The exception is the Groundwater Protection scenario where commercial water demand in Algonquin and Nunda townships is significantly lower than the rest and higher in Grafton township. These trends are a result of a combination of existing commercial development and new commercial development expected to occur during the study period. Note the scale as compared to residential water demand.
Figure 5: Change in agricultural water use across scenarios.
Changes in agricultural water demand remain relatively flat across scenarios and townships. The main exception being the Green Infrastructure scenario where Coral and Greenwood townships see the largest reduction in agricultural water demand during the study period. This is likely because of a reallocation of development into agricultural lands as green infrastructure areas are less available for accommodating new development; new development will occur, but agricultural lands will be converted before IDNR and Chicago Wilderness green infrastructure areas.
Ag preservation districts
40 acre zoning
Land evaluation districts
Compact Contiguous Growth
Short-term transportation projects
Financially constrained transportation projects