Evaluation of the reduction in the water storage capacity of Black Lake, AK

Abstract

The paper provides a systematic evaluation of the causes that trigger reduction of a lake's water storage volume. This evaluation is demonstrated herein through combined numerical analysis and field work conducted on the south side of the Alaska Peninsula to address the reduction in the water storage volume of Black Lake. The contribution of this research was the development of an integrated approach that adequately quantifies the causes of reduction of water storage volume of lakes. For this purpose, a set of established routing, erosion, riverine, and lake models were integrated to identify quantitatively the causes of the Black Lake water storage reduction. Selection of the models was a compromise between their complexity, compatibility, capability, and available input data. The results of this study suggest that contrary to what has been long thought the lake receives sufficient water influx to maintain its maximum storage capacity. In addition, sedimentation was not found to the cause, because siltation since 1950 has reduced the storage capacity by only 1.0%. The reduction in the lake storage was mainly attributed to severe degradation at the lake outlet. The outlet elevation of the lake has decreased by at least 1.0 m over the past 55 years. This study recommended that a gated weir could be used as a control structure to maintain the elevation at the lake's outlet. In addition, an erosion model predicted that the lake may loose 80% of its current storage capacity within a 100‐year period causing a complete destruction of the ecosystem, if no action is taken.