Stormwater Quality Management in the Tahoe Basin under a Changing Climate

Abstract Submission: Due to decades of documented clarity loss, Lake Tahoe is designated an impaired water body under the Clean Water Act. This designation led to development of a Total Maximum Daily Load (TMDL) and the aggressive implementation of stormwater control measures to reduce fine sediment particle and nutrients. Climate change in the Tahoe Basin has the potential to produce larger and more intense storm events as well as more winter precipitation falling as rain, which could lead to an increase in runoff volumes and loads to the lake. To offset this change, stormwater infrastructure may need design adjustments to remain effective for larger and more frequent runoff events. Research was conducted to evaluate how BMPs sized for the current design storm may be impacted by a changing climate. Projected temperature and precipitation from a locally downscaled global climate model were applied to a continuous simulation hydrologic model. Changes in runoff volumes, rates, and volumetric percent capture for BMPs located in three different areas of the Tahoe Basin were evaluated for current conditions and a near future period (2030-2060). The study found that within the next 30 years the duration of seasonal snowpack will likely be reduced and the volume of runoff is expected to increase by 30-40%. In addition, although median flow rates are not expected to significantly change in the future, extreme events will become more frequent leading to a reduction in long-term, volumetric percent capture of stormwater in BMPs. This presentation will describe the approach and findings from this study along with recommendations for designing BMPs that will be more resilient to the effects of climate change and more effective at reducing fine sediment particles and nutrients.

Learning Objectives/Expected Outcome (Optional) : Approach for using locally downscaled global climate model data for continuous simulation modeling of stormwater
Potential impacts of climate change on stormwater management in the Tahoe Basin
BMP design considerations to improve resiliency and performance