Research Abstract

The Devils Lake outlet projects in North Dakota, USA have been successful in mitigating regional flooding issues over the past decade. However, as the highly saline water (with especially high sulfate concentration) from the Devils Lake flowed into the nearby Sheyenne River, the river inevitably suffered from an increase of water salinity, which could bring negative environmental and economic impacts to the region. Previous studies have estimated the costs of the Devils Lake flooding adaptations, this study aims to identify and estimate the potential damages from the increasing water salinity of Sheyenne River, multiple aspects including agricultural activities (crop yield loss, cost in advancing irrigation), recreational activities (loss in fishing and sightseeing) and daily water usage (costs for new water treatment plants) will be assessed in estimating the damages. By comparing the costs between the Sheyenne River salinity damages and the Devils lake flooding mitigation, we aim to further evaluate the regional economic trade-offs under the outlet projects and provide insights for future policymaking.

Research Highlights

The Devils Lake (DL) outlet projects in North Dakota have been effective in mitigating regional flooding over the past decade. However, with the highly saline water pumped from Devils Lake into the nearby Sheyenne River, the water quality degradation has caused societal concerns in sur-rounding communities. This study aims to estimate the monetary costs of the increasing water salinity in the Sheyenne River as the consequence of mitigation measures in combating DL flooding. By comparing the costs of the salinity damages in the Sheyenne River and the benefits received from flooding adaptations in DL, we further evaluate the economic trade-offs of the outlet projects and provide insights for future regional policymaking. Using the benefit transfer method, we monetized the potential impact of DL outlets in the middle and lower Sheyenne River subbasins to be rang-ing from $2,389 to $7,765 per year with every 1 mg/L increase of river salinity. As a tradeoff, reducing the capacity of the outlets to avoid the 1 mg/L increase in the Sheyenne River salinity would have caused an in-crease of 0.012 ft in the DL’s maximum level, which can lead to a cost of $62,796 in protecting the surrounding infrastructures. Thus, our results show that the benefits of the DL outlet project significantly outweigh its costs. While our results support the operations of the Devils Lake outlets, Policymakers should consider population growth and recreational values in future scenarios to better assess the eco-nomic trade-offs of the Devils Lake outlet projects.