Decoupling the Hydroclimatological Conditions before and during the Recent Flooding Event in the Missouri River Basin

The recent flooding event in the Missouri River Basin (MRB) has taken a heavy toll on the society by causing a huge socio-economic loss affecting agriculture, water quality and infrastructure. The objective of this study is to analyze the hydro-climatological condition before and during the flooding event in the MRB. In order to achieve our objective, first, the climatology of snow melt, soil moisture, air temperature and soil temperature, obtained from the North American Regional Analysis (NARR), were calculated for 1979-2018 and then, compared with the daily condition of 13^th of March, 2019 which was the onset of the flooding event. Further, the return periods of the peak stream flow were determined using Extreme Value Theory (EVT) at 14 gauging locations in the MRB. From the preliminary analysis, it was found that the amount of snowfall that accumulated mainly from the second week of February, 2019 contributed significantly to the snowmelt in the middle-lower part of the MRB including Loup, Elkhorn and Missouri Nishnabotna hydrologic units. Whereas, in the upper and central part of MRB, significant amount of snowmelt started to take place after 14^th of March due to increase in daily temperature. In the middle-lower part of MRB, the amount of snowmelt was significantly high (4-44 times) compared to the snowmelt climatology on 13^th of March which was mainly driven by the unusual high daily temperature (3-14°C higher compared to the climatology) on that day. Furthermore, the soil was also saturated and frozen (soil temperature was 4-8°C lower than the climatology) which almost nullified the infiltration to the soil. From the EVT analysis of streamflow, it was found that 3 out of 14 gauging locations showed significantly high return periods of more than 100 years.