Data in the Great Lakes Regional Water Use Database has the following limitations that must be considered when viewing water use information.

1. Direct comparison of water use between jurisdictions is not possible because of the following differences in water use patterns, data collection and reporting:

• Each jurisdiction has unique topographical features, soil characteristics, and precipitation patterns that affect water usage patterns.
• Each jurisdiction has unique inclusion criteria for the quantity or type of water use that is reported. All water users are not represented for every jurisdiction.
• Each jurisdiction borders on a different portion of the basin. The proportion of the district that borders the Great Lakes Basin impacts the number of basin withdrawals.
• Use of measurements or estimates varies by jurisdiction · The level of accuracy of water use data varies by jurisdiction.
• Each jurisdiction follows its own protocol in data reporting and differs in funding support and expertise.

2. Numbers generated by the online database will not necessarily match the figures in the printed report of the database due to rounding of individual water uses and conversions between gallons and liters. However, the two numbers should approximate each other.

3. Quantities of water used are reported as a volume per day. Seasonal patterns of use in some categories mean that the average daily flow is not used every day of the year. It is not possible to obtain a total yearly volume from the information provided.

For example: Irrigation may occur for only a few months. Multiplying the daily flow by 365 will overestimate the total water used for the year. Conversely, daily flows that have been calculated by dividing the yearly total by 365 underestimate the actual use on a given day during irrigation season.

4. Data presented in the search results are from all facilities (including principal facilities that withdraw in excess of 100,000 U.S. gallons/day average over a 30-day period and smaller facilities) as reported by each jurisdiction. 

5. Consumptive use data have the following limitations and, therefore, cannot be used in a comparative analysis: · Data are derived from estimations, using coefficients. · The use of consumptive use coefficients are variable across jurisdictions and water use categories. Refer to consumptive use coefficient table.

Data Source by Jurisdiction

Illinois 

Water use data for Illinois was provided by the Department of Natural Resources - Office of Water Resources, and the State Water Survey. The withdrawal data submitted by the Illinois DNR to the repository were 100 percent measured and 100 percent site-specific. 

Indiana 

The Indiana Department of Natural Resources - Division of Water compiled the 1998 data for the Regional Water Use Database for the Lake Erie and Lake Michigan basins. The Indiana Business Research Center at Indiana University provides population estimates for counties used in calculating self-supply domestic withdrawals. The Indiana Agricultural Statistics service at Purdue University provides livestock estimates by county. The local office of USGS Water Resources Division provides estimates of percent of population by county on domestic wells. Indiana data for 1998 were 4% measured, 50% partially measured, and 46% calculated or estimated. The level of aggregation was 99% site-specific and 1% aggregated. 1997 data was used for the hydroelectric water use category. 

Michigan 

The 1998 water use data for Michigan was submitted to the Regional Water Use Data Base by the Michigan Department of Environmental Quality (DEQ). All data are reported to the Michigan DEQ by the facilities within each category except Irrigation, which is divided into agricultural and nonagricultural (golf course, park, etc.) irrigation. Agricultural irrigation is estimated using federal Agricultural Census data and a water use estimation model developed for Michigan. Nonagricultural irrigation facilities report directly to the DEQ. Michigan did not submit water use data for principal facilities in 1998 due to system limitations, the large number of reporting facilities, and lack of staff resources. Most of the data are available within the state data base, and staff expects to provide breakdowns by principal facilities in subsequent years. Michigan data of base year 1998 was 89% measured, 8% partially measured, 3% estimated, and 100% site-specific.

Minnesota 

The Minnesota Department of Natural Resources Division of Waters provides the data on the Lake Superior Basin to the Regional Water Use Data Base. Minnesota water use data were 100% measured and 100% site-specific.

New York

Water use data collection in New York is performed by the Department of Environmental Conservation (DEC), the Department of Health, and the U.S. Geological Survey. For New York, the data reported were 100% partially measured. The level of aggregation was 100% site-specific.

Ohio 

Water use data for Ohio is collected by the Ohio Department of Natural Resources-Division of Water, the Ohio Environmental Protection Agency, and the U.S. Geological Survey. The 1998 water use data for Ohio were 100% partially measured while the level of aggregation was 100% site-specific. 

Ontario 

The 1998 water use data for the Ontario Great Lakes basin, which includes Lakes Superior, Huron, Erie, Ontario, and the St. Lawrence River, were provided by the Ontario Ministry of Natural Resources (MNR). Public Supply and Industrial data were collected by Environment Canada and shared with MNR. All categories contain water use data from1998 except industrial, livestock and irrigation categories, which contain water use data from 1996. Data for some water users is not available, and this database does not represent all water use in the province. Ontario's withdrawal data for this report were 99.9% partially measured and the level of aggregation was 99.5% site-specific. 

Pennsylvania 

Due to staffing and other programmatic constraints, this report utilizes 1994 data. The Department of Environmental Protection - Bureau of Water Supply and Community Health submitted water use data for the Lake Erie and Lake Ontario Basins of Pennsylvania. The Pennsylvania 1994 data were 50% measured and 50% estimated, with a 98% site-specific level of aggregation. 

Quebec 

Due to staffing and other programmatic constraints, this report utilizes 1993 data. The Ministère de l'Environnement - Centre d'expertise hydrique du Québec provided Quebec water use data The Centre d'expertise hydrique du Quebec is concerned with hydrologic and hydraulic studies, floodplain delineation and mapping and hydrometric network management. Figures submitted to the Water Use Database were collected exclusively for this purpose. 

Wisconsin 

1998 water use data for the Lake Michigan and Lake Superior basins of Wisconsin were submitted by the Wisconsin Department of Natural Resources-Bureau of Water Resources Management. Wisconsin's 1998 water use data was 100% calculated or estimated. The level of aggregation was 100%.