Water quality in the Truckee River is challenged by low stream flows and competing water demands. LimnoTech is supporting several regional agencies in a third-party effort to review and potentially improve numeric nutrient water quality standards and a 1994 TMDL. Driving factors motivating the effort include improved river flow operations, advances in understanding the science of river processes, and a desire for more flexible solutions to water quality management.
LimnoTech developed a publicly available water quality model, Truckee River HSPF (TRHSPF), to predict occurrences of low dissolved oxygen resulting from nutrient inputs, benthic algae growth, and the effects of low flow conditions. A watershed model, WARMF, was applied to the Truckee River watershed to forecast nonpoint source loads under current and future land use, and to project potential nonpoint load reductions. WARMF-predicted tributary flows and nonpoint source loads are inputs to TRHSPF. The linked and calibrated WARMF‐TRHSPF models were applied to evaluate potential nitrogen and phosphorus water quality criteria with inputs derived from a flow management model representing typical low flow and average flow conditions.
LimnoTech’s analysis is helping Nevada regulators identify numeric nutrient water quality criteria that are protective of beneficial uses. As part of an anticipated TMDL review, LimnoTech will further use the modeling tools to evaluate the Truckee River’s assimilative capacity and response to nutrient loading under a range of flow conditions. The analysis will examine TMDL allocation alternatives and consider potential improvements from stream restoration. A revised Truckee River TMDL will provide unique opportunities for flexible, equitable water quality improvement and support for regional growth.