Status of the Souris River
It was apparent early in 2011 that moisture conditions over the Souris River drainage were abnormally high. Conditions deteriorated due to additional snow and rain, eventually leading to the most catastrophic flood in the history of the Souris.
While it is too early to accurately assess runoff possibilities in the Souris in 2013, there are some indicators that are deserving of close attention from now through completion of the runoff season.
Lake Darling is the final collection point above Minot for the majority of water that enters the Souris River Basin each spring. Therefore, the amount of water backed up behind Lake Darling Dam is of importance to river interests in the Minot region and downstream.
Lake Darling’s official reading Thursday afternoon was 1,596.01 feet with a release rate of 70 cubic feet per second. 1,596 feet is the level set by the International Souris River Board for winter operation of Lake Darling. It is the same level that was in effect during the flood year of 2011.
According to a spokesman at the Upper Souris National Wildlife Refuge where Lake Darling is located, the release rate from Lake Darling Dam was increased from 50 cfs to 70 cfs on Jan. 16 and is scheduled to continue indefinitely. The releases were in response to similar flows being released from Rafferty and Alameda reservoirs in Saskatchewan. Those flows have essentially been captured by Lake Darling. Releases from Rafferty and Alameda were at 18 cfs each Thursday.
The flow in the Souris at Sherwood, the first gauging station on the river below the Saskatchewan/North Dakota border, peaked about Feb. 10 and has since begun to fall. The difference between the most recent peak and the current flow is about half a foot.
The releases from the Saskatchewan reservoirs were for the purpose of dropping those key storage facilities to operating levels indicated by the ISRB, again the same requirements that were in place in the spring of 2011.
As of Thursday Rafferty Reservoir, located near Estevan, Sask., stood at 1,802.78 feet. Rafferty is required to be no higher than 1,802.91 feet at this time of year. Alameda was recorded at 1,840.35 feet Thursday versus a prescribed operating level of 1,840.64 feet.
The Saskatchewan Water Security Agency released its initial Spring Runoff Potential outlook Feb. 1. It reveals a growing concern over “well above normal” areas of spring runoff and an “above normal” outlook for nearly the entire southern half of Saskatchewan. The headwaters of the Souris River and Moose Mountain Creek, which join to flow into the Souris before it enters North Dakota, are on the fringe of an area identified as containing “well above normal” runoff potential.
According to the WSA, the amount of moisture contained in the identified “well above normal” regions is 200 percent of normal, with much of the province listed “generally 150 to 200 percent of average for this time of year.”
It should be noted that much of the southern agricultural land in Saskatchewan went into freeze-up with dry soil conditions; the province was unusually wet in the fall of 2010. Additionally, it is emphasized that at least two more months of the winter season remain and conditions are subject to significant variations throughout that time period.
The Saskatchewan WSA puts it this way, “Above normal precipitation prior to runoff and/or a faster than typical rate of melt will result in significantly higher runoff. Projected runoff is based on sparse, variable and often conflicting snow accumulation estimates. In many areas conditions vary considerably over short distances.”
To date, no definitive forecast has been issued regarding potential runoff scenarios for the Souris River Basin. Forecasts containing the latest and most accurate information, both from the National Weather Service and the Saskatchewan Water Security Agency, can be expected to begin in March and continue throughout the runoff season.