Determining the effectiveness of best management practices to reduce nutrient loading from cattle grazed pastures in Utah Nicki Devanny Utah State University, MS Watershed Science Adviser: Nancy Mesner

Water Pollution Management Point source pollution: easily identified, monitored, and treated Nonpoint source pollution: difficult to identify, monitor and treat Recommended best management practices (BMPs) Effective?

Objectives 1)Develop local, field scale nutrient loading coefficients and evaluate the effectiveness of best management practices (BMPs) on cattle grazed pastures

Objectives 1)Develop local, field scale nutrient loading coefficients and evaluate the effectiveness of best management practices (BMPs) on cattle grazed pastures 2)Build a model with the Soil and Water Assessment Tool (SWAT) for field sites to predict current and potential loads of other fields within the watershed

Objectives 1)Develop local, field scale nutrient loading coefficients and evaluate the effectiveness of best management practices (BMPs) on cattle grazed pastures 2)Build a model with the Soil and Water Assessment Tool (SWAT) for field sites to predict current and potential loads of other fields within the watershed 3)Develop outreach tools

Current site management About 200 acres Flood irrigated pasture with cattle access to stream About 180 head of cattle from May- September

Existing Impairments at Field Site Channelized stream Extreme bank erosion Loss of irrigation diversions Cattle access to stream Lack of riparian vegetation

Best Management Practices Mitigate stream velocity Reduce erosion potential Remove stressors Filter return tailwaters

Objectives 1)Develop local, field scale nutrient loading coefficients and evaluate the effectiveness of best management practices (BMPs) on cattle grazed pastures

2014 Control Impact Instream Water Sample Collection berm Runoff Water Sample Stream Restoration BMPs 2015

2014 Control Impact Collection ditch Runoff Water Sample Instream Water Sample Stream Restoration BMPs Shallow Wells 2015

Water Sample Analysis USU Aquatic Biogeochemistry Lab Phosphorus: TP, DTP, SRP Nitrogen: TN, DTN, Ammonium, Nitrate/Nitrite Total Suspended Solids E. Coli

Nutrient Loading Coefficient Calculate load for each chemical component – Chemical Concentration (mg/L) * Flow (f 3 /s) – kg/day Calculate average loading coefficient for each chemical component – Load (kg/day) * Area (ha) – kg/ha/yr From this calculate nutrient ratios and changes

Objectives 1)Develop local, field scale nutrient loading coefficients and evaluate the effectiveness of best management practices (BMPs) on cattle grazed pastures 2)Build a model with the Soil and Water Assessment Tool (SWAT) for field sites to predict current and potential loads of other fields within the watershed

Soil and Water Assessment Tool Used extensively to calculate impairment reductions for TMDL reports. Can be used for multiple scales – Subbasins – Reaches – Impoundments – Point source

SWAT Input Watershed dimensions Climate Hydrologic cycle Sediment Nutrients Pesticides Bacteria Plants Management Channel processes Impoundment processes

SWAT Output Nutrient Loads (kg/ha/yr) – Total N – Ammonia – Nitrate – Organic N – Total P – Soluble P – Organic P Annual Averages (kg/ha) – Total N – Ammonia – Nitrate – Organic N – Total P – Soluble P – Organic P Runoff flows Surface, Lateral, Groundwater

Objectives 1)Develop local, field scale nutrient loading coefficients and evaluate the effectiveness of best management practices (BMPs) on cattle grazed pastures 2)Build a model with the Soil and Water Assessment Tool (SWAT) for field sites to predict current and potential loads of other fields within the watershed 3)Develop outreach tools

USU Water Quality Extension Fact Sheet

Soils Climate Irrigation Practices Land Cover and Slope Cattle Density Water Access Load Allocation: (kg/ha/yr) total, reduction InputOutput

Conclusions 1.Provide locally relevant nutrient runoff coefficients 2.Determine if BMPs implemented in cattle grazed pastures will significantly decrease the nutrient load within one year 3.Provide SWAT analysis of nutrient loading at a field scale 4.Scale up results to check the assumptions of predicted TMDL load reductions 5.Provide outreach materials to educate land owners and managers on nutrient loading potential

Thank you… Questions? My committee Nancy Mesner, Dr. Niel Allen, Dr. Sarah Null, as well as the Ashton family, Jeff Dunn, Dr. Neil Hansen (BYU), Sandy Wingert, Daniel Gunnell, and Audree VanValkenberg