A SNAKE RIVER WATERSHED CONDITIONS REPORT Topical Report RSI-2483 Prepared by Megan Burke Emily Javens RESPEC prepared for Middle-Snake-Tamarac Rivers Watershed District 453 North McKinley Street Warren, Minnesota 56762 February 2015 1935 West County Road B2, Suite 320 Roseville, MN 55113 651.788.7813 Snake River Watershed Conditions Report EXECUTIVE SUMMARY The Snake River Watershed Conditions Report describes the watershed’s physical characteristics, provides an overview of its water resources, and describes current water quality conditions. This includes summarizing water runoff (floods to drought), patterns in water quality, potential stressors to the biological integrity of the waterbodies, and information gaps. The development of the conditions report is the first step in building a Snake River Watershed Restoration and Protection Strategy (WRAPS). The ultimate goal of the Snake River WRAPS is to develop and implement strategies to protect waters where conditions meet water quality standards and to restore waters that are impaired. This report and subsequent WRAPS will provide additional knowledge and tools for balancing the needs of intense land uses (agriculture and urban development), including flood reduction with the preserving of ecological functions via watershed-based approaches. Located in the Red River of the North Basin in northwestern Minnesota, the Snake River and Middle River Watersheds drain an area of 611,800 acres (or approximately 956 square miles). The Snake River flow network includes two converging rivers, with the Middle River flowing to the west across the northern portion and joining the Snake River and the South Branch of the Snake River draining lands from the southern portion of the watershed. Both rivers receive runoff from extensive networks of drainage ditches. The Snake River Watershed is managed by the Middle-Snake-Tamarac Rivers Watershed District (MSTRWD). Fine-grained lake sediments deposited in Glacial-age Lake Agassiz provide the rich soils of today that are the basis for agricultural food production, with approximately 70 percent of the land cover in agricultural uses. Wetlands and forested areas exist primarily in the eastern portions of the watershed. Watershed soils and geology vary from west to east across the watershed, in part largely because of the sediment deposition within Glacial-age Lake Agassiz and erosion of its former beach ridge areas. The area’s extreme continental climate can experience wide annual temperature fluctuations and is semi- arid, with the watershed receiving an average of approximately 22 inches of precipitation per year. Combined with annual evaporation of approximately 30 inches, dry periods can result in very low stream flows along with increased irrigational needs and wildfire potential. The highest monthly rainfalls occur in May through September; June has the highest monthly rainfall. Based on the last 30 years of climate data for Argyle, Minnesota, the average number of days between spring and fall frosts is approximately 130 days with no increasing or decreasing pattern evident. Continuous stream flows are being measured at three gages along the Snake River and one long-term, continuous gage on the Middle River, with data dating back to 1945. However, flows are not monitored below the confluence of the Snake and Middle Rivers, likely because of backwatering effects from the Red River of the North. Hence, monitored flows from the continuous gaging sites of the Middle and upper Snake Rivers were used to predict (via modeling) flows from the combined flow network. Considerable seasonal flow variability was noted, for example, with Middle River values ranging from peak spring flows (maximum of 3,500 cubic feet per second [cfs]) to very low- or no-flow conditions typically encountered in late summer and into the fall. These dry periods with very low base flows are a concern for aquatic biota as well as agricultural production. Degraded water quality (sufficient to violate state water quality standards) was identified by the Minnesota Pollution Control Agency (MPCA) for six stream segments within the Snake River Watershed RESPEC RSI-2483 i Snake River Watershed Conditions Report and encompassed the entire length of both the Snake River (five segments) and Middle River (one segment). The causes of impaired water quality for each stream segment vary and include low dissolved oxygen and excessive turbidity on the Middle River and the two most downstream reaches on the Snake River, impaired biota (fisheries) and low dissolved oxygen on Snake River’s third reach, impaired biota (fisheries) and turbidity on the Snake River’s fourth reach, and low dissolved oxygen on the Snake River’s headwater reach. Note that the MPCA has recently promulgated new eutrophication standards and replaced turbidity with total suspended solids (TSS) standards for rivers and streams that were approved by the U.S. Environmental Protection Agency (U.S. EPA) in late January 2015. These standards changes are expected to impact the 2015 stream assessment that will determine impairment listings within Snake River Watershed, which are currently being conducted by MPCA’s professional judgment team. Water quality data were available from 21 monitoring sites located throughout the watershed, although the availability of various parameters varied greatly (e.g., many more stations had temperature data available than phosphorus or chlorophyll a data). Water quality evaluations of dissolved oxygen, turbidity, and TSS conducted by this study reinforced impairment listings previously identified. These evaluations also defined levels of E. coli, pH, and phosphorus that likely violate existing or newly approved river quality standards. The MPCA is currently evaluating the intensive monitoring data from 2012–2014, and updated water quality and biological assessments are expected in early 2015. RESPEC RSI-2483 ii Snake River Watershed Conditions Report TABLE OF CONTENTS 1.0 INTRODUCTION ................................................................................................................ 1 2.0 WATERSHED SETTING ...................................................................................................... 2 2.1 WATER RESOURCES ..................................................................................................... 2 2.1.1 Major Rivers and Streams................................................................................... 2 2.1.2 Lakes and Impoundments .................................................................................. 6 2.1.3 Wetlands ........................................................................................................... 6 2.1.4 Groundwater ..................................................................................................... 6 2.2 LAND CHARACTERISTICS ............................................................................................. 7 2.2.1 Topography ....................................................................................................... 7 2.2.2 Geology and Geomorphology .............................................................................. 7 2.2.3 Soils .................................................................................................................. 10 2.2.4 Ecoregions ........................................................................................................ 10 2.2.5 Natural Resources .............................................................................................. 10 2.3 CLIMATE ..................................................................................................................... 14 2.4 HUMAN INFLUENCES.................................................................................................... 19 2.4.1 Land Use ........................................................................................................... 19 2.4.2 Water Use ......................................................................................................... 21 2.4.3 Drainage Systems .............................................................................................. 21 2.4.4 Drinking Water Source Protection ....................................................................... 26 2.4.5 National Pollutant Discharge Elimination System Permitted Discharge Facilities ...... 26 2.4.6 Socioeconomics ................................................................................................. 28 2.4.7 Local Governments ............................................................................................ 30 2.4.7.1 Watershed Districts ................................................................................ 30 2.4.7.2 County Soil and Water Conservation Districts........................................... 30 3.0 WATER QUALITY STANDARDS AND IMPAIRMENTS ....................................................... 31 3.1 WATER QUALITY STANDARDS ...................................................................................... 31 3.1.1 Aquatic Life Protection Standards ........................................................................ 32 3.1.2 Aquatic Recreation Protection Standards ............................................................. 33 3.2 IMPAIRMENTS ............................................................................................................. 34 4.0 EXISTING DATA AND PREVIOUS WORK.......................................................................... 38 4.1 AVAILABILITY