Groundwater is used in Obama City, Japan, to melt snow (~13% of total groundwater use) during the winter, the remainder being used for mostly domestic purposes, such as drinking water. Due to concern about the impacts of this snow-melting practice on nearshore marine resources, we estimate the benefits and costs of increasing the volume of the groundwater used for snow-melting by 50%. Assuming that the outcome is the same for all possible snow-melting techniques—snow effectively removed from roads—the primary benefit of the use of groundwater for snow-melting is the avoided cost of, or cost savings relative to, alternative technologies. The costs include losses to nearshore fishery productivity, due to a decline in submarine groundwater discharge (SGD), and increased energy expenditures on groundwater pumping, used to supply the snow-melting system. Our results suggest that the net benefit of increasing the use of groundwater to melt snow by 1.5 times its current rate in Obama is positive, and that the annual net benefit ranges from 10.9 million JPY/year to 547.7 million JPY/year. Because the cost of operating the groundwater system is relatively low, the net benefit of continuing to use groundwater for snow-melting becomes negative only if the impact on fishery productivity is substantial.