STREAM WATER USES
This chapter explores both the offstream and instream uses of stream water resources in Minnesota. Offstream uses involve withdrawing water, as for municipal and industrial uses, while instream uses require that water be left in the stream, as for commercial navigation and recreational boating. Conflict among users often erupts on rivers with many competing users due to the interdependence of offstream and instream uses. Offstream uses covered in this chapter are: municipal, thermoelectric, industrial and agricultural uses. Instream uses discussed are: hydropower, commercial navigation, commercial fishing and hunting, recreational boating, other recreational uses and in situ uses such as for natural amenities and waste disposal.
OFFSTREAM WATER USES
The U.S. Geological Survey (USGS) estimates total water use by geographic area and type of use for the United States every five years. The 1995 estimated withdrawals for offstream water uses in Minnesota totaled 3,390 million gallons per day (mgd) (Table 3.1)1. Offstream withdrawals may be for consumptive or non-consumptive use. Consumptive use is defined as water withdrawn from its source and not returned directly to the source (M.S. 103G.005, subd 8). In contrast, water diverted for non-consumptive use is immediately returned to its source after use.
Approximately 79 percent of withdrawals in 1995 came from surface water sources. Although some water is withdrawn from lakes, notably Lake Superior, the majority comes from rivers. Thermoelectric plants constitute the largest single offstream user with 60 percent of total withdrawals, followed by public water supply (14 percent), mining (9 percent) and irrigation (5 percent). Thermoelectric power production returns most of the water withdrawn to surface sources and is considered a non-consumptive use. Groundwater withdrawals make up 55 percent of total withdrawals when non-consumptive use for power generation is excluded.
The Minnesota Department of Natural Resources (DNR) provides annual information on actual withdrawals by users holding water appropriation permits. Under state law, users withdrawing more than 10,000 gallons per day or one million gallons per year must obtain an appropriation permit. Permit holders must report to the DNR each year the volume of water withdrawn, accurate to within 10 percent. Based on these individual reports, the DNR calculates total permitted withdrawals for the state by type of use (DNR, 1997).
________________________________________________________________ Type of Use Surface Ground water Total ________________________________________________________________ ...... million gallons/day (mgd) ..... Public Supply 154 331 485 Domestic 0 88 88 Commercial 20 46 66 Irrigation 37 120 157 Livestock 0 62 62 Industrial 83 58 140 Mining 292 6 298 Thermoelectric 2,090 2 2,090 Total* 2,680 714 3,390 ______________________________________________________________
Source: http://water.usgs.gov/watuse/ * Figures may not add up to totals because of rounding
Table 3.2 shows Minnesota’s total permitted water use for the 1986-95 period. Over this period, total permitted usage trended upward due predominantly to increased thermoelectric demands. Based on available information, permitted use data represent a relatively good proxy for total usage. A comparison of the 1995 U.S. Geological Survey’s total estimated water use of 3,390 mgd with the 1995 DNR total permitted use of 3,277 mgd reveals the two measures of total use are very close. These data also suggest that there are very few small diverters (those withdrawing less than 10,000 gallons per day).
Thermoelectric Power Generation Water Use
The largest volume of surface water withdrawals reported for the 1986-95 period was for nuclear and stream power plant cooling. During this period, Minnesota’s power plants withdrew an average of 1.86 billion gallons of surface water per day. Usage trended upward over the period, increasing 28 percent between 1986 and 1995 (Table 3.2). Approximately 90 percent of total withdrawals for power plants return to their originating source and therefore are defined as non-consumptive use. This means that in 1995 while power plant withdrawals made up about 78% of total surface water withdrawals, consumptive use by power plants was less than 8 percent of total consumptive use (Table 3.1). Sixty-nine percent of reported water use in the state took place in the eight counties where power plant cooling was identified as the primary use. For example, water for cooling power plants in Goodhue and Wright counties accounted for 28 percent of total 1995 reported use for the state (DNR, 1997).
Division of Waters, “1995 and 1996 Water Year Data Summary,” May 1997.
Public Supply Water
Use Public supply includes water distributed to domestic, commercial, small industrial, and public users such as city parks, government buildings and hospitals. It does not include self-supplied domestic users or those served by small water companies (fewer than 25 customers). Withdrawal to meet the demands of this user group varies seasonally in Minnesota. Water usage increases in the summer months because of landscape irrigation and other outdoor uses of water. A rapid increase in demand for public water supplies has accompanied significant growth in Minnesota since the 1950s. While reliance on surface water sources increased until 1980, the majority of public supplies now come from groundwater. Increased dependence on groundwater to meet drinking and other public supply needs has raised new issues for water utility managers related to water quality and long-term sustainability of current withdrawal rates.
Industrial Processing Water Use
Industrial water use includes milling activities, paper and forest product operations, and food processing. It does not include smaller industrial facilities that receive water from public water suppliers. According to 1995 U.S. Geological Survey data, industrial use constituted 4 percent of total estimated water use and 11 percent of total consumptive use (Table 3.1). Surface water sources contribute 60 percent of the water used in industry. The mining industry is the third largest water user in the state with nine percent of total withdrawals and the second largest consumptive user with 23 percent of total.
Annual permitted water use data for industrial processing reported by the Minnesota DNR provide aggregated industrial and mining use data. In 1995, mining-related water-use activities accounted for 65 percent of reported industrial usage, pulp/paper processing for 16 percent and agricultural processing for 7 percent (DNR, 1997). Total water usage for industrial processing increased 33 percent between 1994 and 1995 because of increased mining demands in Lake County (Table 3.2). Counties with the highest industrial processing water use, ranked in decreasing order of use, include: Lake (mine processing), Cook (mine processing), Koochiching (pulp/paper processing), St. Louis (mine processing), Itasca (pulp/paper processing) and Ramsey (general and agricultural processing).
Agricultural Water Use
In 1995, agricultural use accounted for five percent of Minnesota’s total usage and 13 percent of consumptive use (Table 3.2). Although agricultural use is relatively small, most applied water is used consumptively. Most of this water (76%) comes from groundwater sources (Table 3.1).
Irrigation is the primary agricultural use. The DNR’s irrigation category includes major crops, orchard, and nursery irrigation, as well as some uses that are not agricultural, such as landscaping, cemetery, and golf course irrigation. Major crops accounted for 77 percent of total use in 1995 (DNR, 1997). Virtually every county in the state reports irrigation water use to the DNR. Otter Tail and Sherburne Counties reported the highest irrigation water use in 1995 with 17 percent and 12 percent of total irrigation use, respectively.
Livestock watering and other on-farm water uses make up most of non-irrigation use. Non-irrigation uses generally do not require a DNR permit because they constitute a relatively minor usage. The U.S. Geological Survey estimated 1995 livestock usage at 62 million gallons per day or five percent of consumptive use (Table 3.1).
Other Offstream Water Uses
Other uses as defined by the Minnesota DNR include air conditioning, water level maintenance, fisheries, construction dewatering, pollution confinement and other specialty uses (DNR, 1997). In 1995, these uses represented only five percent of total permitted use.
footnote 1. Under M.S. 103G.005, subd. 8, all groundwater withdrawals not returned to the same aquifer are considered consumptive use. Surface withdrawals are considered consumptive use if they are not directly returned to the originating source so that it is immediately available for further use (DNR, 1997).