Determining the effectiveness of best management practices to reduce nutrient

loading from cattle grazed pastures in Utah

Nicki DevannyUtah State University, MS Watershed

ScienceAdviser: 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

Objectives1) 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

Objectives1) 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

2014ControlImpactInstream Water SampleCollection bermRunoff Water SampleStream Restoration BMPs

2015

2014ControlImpactCollection ditchRunoff Water SampleInstream Water SampleStream Restoration BMPsShallow 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 (f3/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

Objectives1) 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

Objectives1) 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

Input Output

Conclusions1. 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