Lake flooding and synoptic weather-type frequency at Devils Lake, North Dakota, USA, between 1965 and 2010

Since the spring of 1993, the water surface elevation at Devils Lake, a terminal lake in eastern North Dakota, USA, has risen by 8.8 m, producing more than 1 billion USD in direct flood damages. We examine the relationship between weather-type frequencies at Bismarck, North Dakota, and lake volume changes from 1965 to 2010 using the Spatial Synoptic Classification (SSC) system. First, we find statistically significant changes in the frequency of selected weather types over both annual and seasonal time periods. This indicates a trend toward increased advection of more humid weather types that is consistent with the historical rise in lake level. Second, a comparison of weather type frequencies between a subset of years with extreme large and small lake surges, and extreme large and small lake drawdowns, shows that weathertype frequency plays an important role in explaining annual lake volume fluctuations. The results support a climatic explanation for the historical lake rise at Devils Lake, but the relationships are not as strong as might have been anticipated given the unprecedented lake rise that occurred during the study period. A more detailed examination of the complex and non-linear nature of the lake water balance may be needed to further clarify how precipitation input is translated into lake volume changes.