Upland contribution of sediment and runoff during extreme drought: A study of the 1947–1956 drought in the Blackland Prairie, Texas

The 1950s drought severely impacted a 1.1 million km2 area in the central US. This drought, along with the famous 1930s drought, was among the most severe of the 20th century for large areas and is the drought of record for water supply planning in Texas. At the USDA-ARS Riesel Watersheds during the drought, average annual rainfall was reduced 27%, which produced 75% less runoff and 35% less sediment yield. Rainfall intensity during the drought was, however, typically greater than for the non-drought period. Based on long-term data from the Riesel Watersheds, the mean, 75th, 90th, and 95th percentile values of sediment yields on days with measurable soil loss were larger for the drought than non-drought periods. These results reflect the increase in rainfall intensity during the drought but more importantly the increased efficiency of drought rainfall to dislodge and transport sediment, which is attributed to the combined effects of reduced vegetative cover and increased soil erodibility. The potential for high sediment yields during drought periods illustrates the need to consider this landscape vulnerability in long-term planning and assessment and the importance of long-term monitoring to predict water supply impacts. This is especially evident in Texas, which is expected to experience a dramatic increase in population and water demand this century, with a corresponding decrease in reservoir storage capacity due to sedimentation

EM-122 Vegetated treatment areas: Reducing soil, nutrient, & bacteria runoff from small hog farms

Vegetated Treatment Areas (or VTAs) are composed of perennial grasses used to improve runoff water quality associated with livestock, poultry, and other agricultural operations. 70-75% of swine operations nationwide are considered ‘small’ with less than 100 head. Producers need practical, low-cost waste management options to protect local water resources. VTAs are inexpensive alternatives compared to standard waste management systems (i.e. lagoons, etc.), and they help reduce soil, nutrient, and bacteria runoff from small operations with small acreage

EM-122 Vegetated treatment areas: Reducing soil, nutrient, & bacteria runoff from small hog farms

Vegetated Treatment Areas (or VTAs) are composed of perennial grasses used to improve runoff water quality associated with livestock, poultry, and other agricultural operations. 70-75% of swine operations nationwide are considered ‘small’ with less than 100 head. Producers need practical, low-cost waste management options to protect local water resources. VTAs are inexpensive alternatives compared to standard waste management systems (i.e. lagoons, etc.), and they help reduce soil, nutrient, and bacteria runoff from small operations with small acreage

Evaluating, interpreting, and communicating performance of hydrologic/water quality models considering intended use: a review and recommendations

Previous publications have outlined recommended practices for hydrologic and water quality (H/WQ) modeling, but limited guidance has been published on how to consider the project's purpose or model's intended use, especially for the final stage of modeling applications namely evaluation, interpretation, and communication of model results. Such guidance is needed to more effectively evaluate and interpret model performance and more accurately communicate that performance to decision-makers and other modeling stakeholders. Thus, we formulated a methodology for evaluation, interpretation, and communication of H/WQ model results. The recommended methodology focuses on interpretation and communication of results, not on model development or initial calibration and validation, and as such it applies to the modeling process following initial calibration. The methodology recommends the following steps: 1) evaluate initial model performance; 2) evaluate outliers and extremes in observed values and bias in predicted values; 3) estimate uncertainty in observed data and predicted values; 4) re-evaluate model performance considering accuracy, precision, and hypothesis testing; 5) interpret model results considering intended use; and 6) communicate model performance. A flowchart and tables were developed to guide model interpretation, refinement, and proper application considering intended model uses (i.e., Exploratory, Planning, and Regulatory/Legal). The methodology was designed to enhance application of H/WQ models through conscientious evaluation, interpretation, and communication of model performance to decision-makers and other stakeholders; it is not meant to be a definitive standard or a required protocol, but together with recent recommendations and published best practices serve as guidelines for enhanced model application emphasizing the importance of the model's intended use