Interflow and Tile Flow Analysis for the Minnesota River Basin FINAL

This memorandum discusses hydrologic components contributing to streamflow during periods when Total Suspended Solids (TSS) exceeds criterion concentrations in the Minnesota River Basin (MRB). This deliverable is for Objective 2, Task C of Modeling Support for the Minnesota River Basin Sediment Reduction Strategy Updates. In Task A, linked Hydrologic Simulation Program Fortran (HSPF) models of MRB watersheds (Tetra Tech, 2016) were used to identify and characterize TSS exceedances for major tributaries to the Minnesota River (Tetra Tech, 2018). The mouths of analyzed tributary streams are classified as type 2B, warm water/cool water, and the Minnesota Water Quality Standard for TSS for type 2B segments specifies a target TSS concentration of ≤ 65 mg/L with an exceedance frequency of ≤ 10% between April - September (https://www.revisor.mn.gov/rules/?id=7050.0222).