Water Storage in the Minnesota River Basin Development of HSPF Model Hydrology-Based Priority Maps for Water Storage: Report 2A

The objective of this task was to use hydrologic considerations derived from existing Hydrologic Simulation Program-FORTRAN (HSPF; Bicknell et al. 2014) models to map the relative potential for reducing peak flows and annual flows to guide where water storage practices can be most effectively implemented in the Minnesota River Basin. Using the watershed HSPF models in the Minnesota River Basin, Tetra Tech determined subwatersheds where river flows have been disproportionately high over past years. Models were developed at the scale of a subbasin within the U.S. Geological Survey’s system of hydrologic units1; a subbasin is the 4th level of the hydrologic unit system and is assigned an eight-digit hydrologic unit code (HUC). These models (one for each HUC8 subbasin) have been developed through multiple iterations by Tetra Tech and RESPEC and were most recently re-calibrated for the 1995 -2012 period (Tetra Tech 2016). Output from the HSPF models was used to develop maps across the entire basin to display prioritization at two scales – the Minnesota River Basin-wide scale and then within each HUC8. Prioritization scales were classified as high, moderately high, moderate, moderately low, and low priority areas based on contributions of flows to the HUC8 outlet.