Poplar and Red Basins

The Poplar River (Figure 2) rises in Saskatchewan and flows southward, joining the Missouri River at Poplar, Montana. Roughly one-third of the basin is in Canada. The entire surface area of the basin is only 8620 km2. Because annual evapotranspiration usually exceeds precipitation, the climate is considered semiarid. The mean annual flow of the Poplar, where it joins the Missouri, is 3.8 m3/s, about three-quarters of that occurring as spring snowmelt runoff (IJC, 1978). This is equivalent to only 13 mm on the surface area of the basin. Significant variations in flow occur both within years and between years. At the international boundary, the natural flow of this river ranges from zero in the summer and autumn months to the record high monthly maximum of 19.9 m3/s in April 1952. Since the 1990s, the maximum streamflow has

Cookson Reservoir Saskatchewan
Figure 2 Poplar, Red River, and Great Lakes basins.

shifted to March instead of April (Environment Canada, 2002).

The sparsely populated Poplar basin is primarily agricultural. The main water uses are irrigated agricultural land in Montana and cooling of a thermal electric generating station in Saskatchewan.

The Red River (Figure 2), known officially as the Red River of the North in the United States, originates as the Otter Tail and Bois de Sioux Rivers in Minnesota and South Dakota, respectively, and flows northward into Canada, forming the boundary between Minnesota and North Dakota. In Canada, the river flows into Lake Winnipeg, the ninth largest lake in the world, and then to Hudson Bay via the Nelson River. Almost 90% of the 116,500 km2 basin, exclusive of the Assiniboine River, lies in the United States, largely in North Dakota and Minnesota.

The Red River basin has a subhumid to humid continental climate. Runoff is dominated by spring snowmelt and varies within and between years. Flows can vary from near zero to more than 3000 m3/s. The most recent low-flow years occurred in the late 1980s and early 1990s (Environment Canada, 2002).

Water uses in the Red River basin are generally for municipal, rural, and industrial purposes (Krenz and Leitch, 1998). The basin supports an extensive and prosperous dryland agricultural industry. The basin is also home to approximately one million people.

Because of the continuing potential for water use conflicts along the Canada-U.S. transboundary, streams that cross the international boundary are closely monitored. An example of a historic water use conflict on the Poplar occurred in 1972. The Saskatchewan Power Corporation applied for water rights on the East Poplar River to support the operation of a thermal electric generating station. This required the construction of a reservoir capable of retaining 40 million m3 of water, roughly 35% of the mean annual flow in the basin.

As a result of an IJC investigation (IJC, 1978), the waters of the Poplar River are apportioned between Canada and the United States. The IJC's apportionment recommendations (adhered to but not formally accepted by the two countries) call for the waters of the basin to be divided equally between the two countries but for an asymmetric distribution among the three tributaries to accommodate the cooling water requirement on the East Poplar.

The transboundary effects of the generating station are monitored by a binational committee (Poplar River Bilateral Monitoring Committee [PRBMC]). These effects relate to groundwater and to surface water quality. Several water quality parameters are monitored, particularly boron and total dissolved solids, and compared to water quality objectives designed to prevent harm to existing water uses in the United States (PRBMC, 2002).

Recently, flooding has been the key issue on the Red River basin (IJC, 2000), but the basin has experienced droughts as well. Although no formal international agreements exclusively cover the Red River (Bruce et al., 2003), concerns that untreated or poorly treated municipal and industrial effluents entering the Red River from the United States may be impairing water uses in Canada led to a limited set of agreed-upon water quality objectives at the international boundary in 1969. The IJC established a board, now known as the International Red River Board (IRRB), to administer the objectives and report to governments (IRRB, 2002).

Canada has also expressed great concern regarding the potential effects, in particular on the aboriginal and commercial fishery of Lake Winnipeg, of proposed North Dakota water projects such as the Garrison Diversion Unit on Canadian waters. The proposed projects divert water from the Missouri basin to the Hudson Bay basin, and the concern is two-fold: degradation of water quality and the introduction of invasive species (IJC, 1977; Kellow and Williamson, 2001).

Multi-decadal droughts occurred in the region before European settlement. Lake salinity records covering 2000 years are used as proxy drought data for Moon Lake, North Dakota (Liard et al., 1996). The records indicate that multi-decadal droughts occurred before AD 1200 but not in subsequent years. Further evidence (Sauchyn and Beaudoin, 1998) indicates that the 20th century was relatively benign clima-tologically and confirms that decade-long droughts occurred before European settlement. Rannie (1999) identifies only two 3-year droughts in the pre-instrumental historical record (1793-1870) for the Red River: 1816-18 and 1862-64.

In more recent times, droughts have affected water use. For example, during a prolonged dry period beginning in 1987, groundwater pumping was used to mitigate decreased volumes and degraded water quality of the Cookson reservoir in the East Poplar River (PRBMC, 2002). The societal impacts of the recent droughts (1987-88 and 2000-02) have not been thoroughly documented for the Poplar and Red basins. The flows of both streams were severely reduced during the late 1980s, with effects on agricultural production and municipal and industrial water supplies, and decreased assimilative capacity.

Although both the Poplar and Red basins are susceptible to drought events, no comprehensive drought management plans exist for either basin. The primary public and institutional response to Red River water quantity problems is to augment supply through importation from the Missouri basin (Fargo Forum, 2003).

Future climate change will have an impact on available water in both the Poplar and Red basins. The Poplar basin is projected to have a 2-4°C temperature increase by the 2050s from the 1961-1990 averages. By the 2080s, the basin's temperature is projected to increase by 3-6°C. The CGCM2 and CSIRO model runs indicate that the majority of the warming will be in the winter and spring whereas the HADCM3 indicates that the summer and fall seasons will have the largest amount of warming. Precipitation amounts are expected to increase on an annual basis in both the 2050 and 2080 periods. However, the summer season is projected to have less precipitation than what was received in the 1961-1990 period (Canadian Institute of Climate Studies, 2003).

The Red River basin is projected to have a temperature increase of 2-4°C in the 2050s and 3-7°C in the 2080s. Annual precipitation values are expected to be below the 1961-1990 values for the 2050 and 2080 periods for the CGCM2 and CSIRO model runs and close to the 1961-1990 values for the HADCM3 model. The largest decrease in precipitation is projected to be in the summer (Canadian Institute of Climate Studies, 2003).

The result of these climatic changes will be that the prairies, on average, will likely experience significantly reduced spring runoff with the possibility of more severe summer rainfall events. Decreased water availability will lead to greater likelihood of transboundary conflicts concerning water use.

There are a number of potential consequences for the Poplar basin. First, on-farm water demands could increase. Canadian demands could match or exceed the entitlement under the current apportionment arrangement. Irrigation water demands in the United States, as well as other on-farm demands, would likely increase. Water use in the United States may be further affected by Montana water rights administration. Under the principle of prior apportionment (Lucas, 1990; Wolfe, 1996), the water rights associated with the Fort Peck Indian Reservation are senior rights, and the needs of the reservation (IJC, 1978) must be met before those of irrigators between the reservation and the international boundary. The response to such a situation could be to attempt to renegotiate the apportionment arrangement with Canada at a time when Canadian farmers are also facing water shortages.

Second, a suite of potential problems is associated with the generating station in Canada. Under drought conditions, the quantity of cooling water in Cookson reservoir would be insufficient to cool both units at the generating station. Therefore, as reservoir water temperatures increase, the plant must be de-rated. Further, during periods of low inflow, the water quality in Cookson reservoir steadily degrades through evaporation until it may exceed the water quality objective for total dissolved solids, and thus affect use of the water released to the United States.

The onset of prolonged droughts in the Red River basin as projected with climate change scenarios will lead to increased water demands for municipal and industrial purposes. The communities in the Red River basin in the United States are abundant water users, with per capita use in Fargo much greater than that in Winnipeg or desert cities such as Tuscon (Fargo Forum, 2001; D. Griffen, personal communication, 2001). One could assume that the effects of drought may be met through water conservation.

There may also be a problem with the lower flows in the Red River and its ability to assimilate municipal wastewater, especially considering the large population along the river. The quantity of water may become an issue even with urban conservation measures. At present, irrigation water demand in the basin is minor, but an increase in irrigation development on account of drought would have a profound effect on water supplies. Irrigation return flows may also affect water quality.

An increase in water demand of that magnitude would lead to Canadian pressure to formally apportion the waters of the Red River between the two countries, as is done for other prairie basins. This task would be complex of itself because North Dakota and Manitoba administer water rights on the basis of prior apportionment, but Minnesota uses riparian water law (Lucas, 1990). More important, increased water demands on the Red River may well lead to increased pressure to divert water from the Missouri River to meet agricultural and other needs in North Dakota, rather than curtailing water uses as would be required under apportionment or conservation measures. This pressure to divert water raises concerns over degradation of water quality and the introduction of invasive species.

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