MODELING SEDIMENT TRAPPING IN A VEGETATIVE FILTER ACCOUNTING FOR CONVERGING OVERLAND FLOW

Vegetative filters (VF) are used to remove sediment and other pollutants from overland flow. When modeling the hydrology of VF, it is often assumed that overland flow is planar, but our research indicates that it can be two-dimensional with converging and diverging pathways. Our hypothesis is that flow convergence will negatively influence the sediment trapping capability of VF. The objectives were to develop a two-dimensional modeling approach for estimating sediment trapping in VF and to investigate the impact of converging overland flow on sediment trapping by VF. In this study, the performance of a VF that has field-scale flow path lengths with uncontrolled flow direction was quantified using field experiments and hydrologic modeling. Simulations of water flow processes were performed using the physically based, distributed model MIKE SHE. A modeling approach that predicts sediment trapping and accounts for converging and diverging flow was developed based on the University of Kentucky sediment filtration model. The results revealed that as flow convergence increases, filter performance decreases, and the impacts are greater at higher flow rates and shorter filter lengths. Convergence that occurs in the contributing field (in-field) upstream of the buffer had a slightly greater impact than convergence that occurred in the filter (in-filter). An area-based convergence ratio was defined that relates the actual flow area in a VF to the theoretical flow area without flow convergence. When the convergence ratio was 0.70, in-filter convergence caused the sediment trapping efficiency to be reduced from 80% for the planar flow condition to 64% for the converging flow condition. When an equivalent convergence occurred in-field, the sediment trapping efficiency was reduced to 57%. Thus, not only is convergence important but the location where convergence occurs can also be important

Neonicotinoid pesticide and nitrate mixture removal and persistence in floating treatment wetlands

Mesocosm and microcosm experiments were conducted to explore the applicability of floating treatment wetlands (FTWs), an ecologically based management technology, to remove neonicotinoid insecticides and nitrate from surface water. The mesocosm experiment evaluated three treatments in triplicate over a 21-d period. Floating treatment wetland mesocosms completely removed nitrate-N over the course of the experiment even when neonicotinoid insecticides were present. At the completion of the experiment, 79.6% of imidacloprid and degradation byproducts and 68.3% of thiamethoxam and degradation byproducts were accounted for in the water column. Approximately 3% of imidacloprid and degradation byproducts and 5.0% of thiamethoxam and degradation byproducts were observed in above-surface biomass, while ∼24% of imidacloprid and degradation byproducts, particularly desnitro imidacloprid, and \u3c0.1% of thiamethoxam and degradation byproducts were found in the below surface biomass. Further, 1 yr after the experiments, imidacloprid, thiamethoxam, and degradation byproducts persisted in biomass but at lower concentrations in both the above- and below-surface biomass. Comparing the microbial communities of mature FTWs grown in the presence and absence of neonicotinoids, water column samples had similar low abundances of nitrifying Archaeal and bacterial amoA genes (below detection to 104 ml−1) and denitrifying bacterial nirK, nirS, and nosZ genes (below detection to 105 ml−1). Follow-up laboratory incubations found the highest denitrification potential activities in FTW plant roots compared with water column samples, and there was no effect of neonicotinoid addition (100 ng L−1) on potential denitrification activity. Based on these findings, (a) FTWs remove neonicotinoids from surface water through biomass incorporation, (b) neonicotinoids persist in biomass long-term (\u3e1 yr after exposure), and (c) neonicotinoids do not adversely affect nitrate-N removal via microbial denitrification

G96-1307 Bioengineering for Hillslope, Streambank and Lakeshore Erosion Control

This NebGuide describes bioengineering techniques for hillslope, streambank and lakeshore erosion control. Tips for a successful bioengineering installation and demonstration project are described. Soil erosion occurs whenever water meets land with enough force to move soil. Often this occurs along streambanks and lakeshores or where excess water flows over hillslopes. While streambank and hillslope erosion can be dramatic, especially after large rainfalls or floods, normal streamflows, excess runoff from urbanized areas and wave action along lakeshores continually erode soil. Erosion can be severe, as is the case in many man-made lakes, where shorelines are composed of easily erodible soil. Traditional methods of controlling streamflow and wave induced erosion have relied on structural practices like rip rap, retaining walls and sheet piles. In many cases these methods are expensive, ineffective or socially unacceptable. An alternative approach is bioengineering, a method of construction using live plants alone or combined with dead or inorganic materials, to produce living, functioning systems to prevent erosion, control sediment and provide habitat. Bioengineering uses combinations of structural practices and live vegetation to provide erosion protection for hillslopes, streambanks and lakeshores. Bioengineering is a diverse and multi-disciplinary field, requiring the knowledge of engineers, botanists, horticulturalists, hydrologists, soil scientists and construction contractors. It is a rapidly growing field, subject to innovations and changing design specifications. Terms such as biotechnical erosion control, biostabilization or soil-bioengineering are often used synonymously with bioengineering

NF01-460 Total Maximum Daily Loads, TMDLs, for Surface Water Pollutants: What They Mean to Nebraska Agriculture

What is the TMDL Process? A Total Maximum Daily Load (TMDL) is a written plan specific to a pollutant and a body of water that incorporates water quality monitoring data, exceedence frequency, sample time flow conditions, and the sources that may be contributing to the water quality problem. Its purpose is to identify pollution sources and propose a plan that will help achieve water quality standards for the body of water. The Clean Water Act calls for the Environmental Protection Agency (EPA) to work with state agencies which in turn work with interested parties in an effort to develop TMDLs to clean up the polluted body of water. Water quality standards are set by states, territories and tribes. They identify the uses for each body of water, such as drinking water supply, contact recreation (swimming) and aquatic life support, and the water quality criteria to support that use

NF05-632 Protecting Your Watershed

Everyone lives in a watershed. A watershed is the land area that contributes water to a location, usually a stream, pond, lake or river. Everything we do on the suface of our watershed impacts the water quality of our streams, wetlands, ponds, lakes and rivers. Like organs in a body, every part of the watershed is essential. What happens in one part affects other downstream parts. This NebFacts discusses the threat of pollutions in our watersheds, common runoff pollutants, and best management practices for protecting the watershed

NF98-375 What is the Cooperative Agreement for Endangered Species Habitat Along the Central Platte River?

The governors of Nebraska, Colorado and Wyoming and the Secretary of the Interior signed a historic agreement on July 1, 1997. This agreement addresses endangered species issues affecting the Platte River Basin upstream of its confluence with the Loup River. The Cooperative Agreement for Platte River Research and Other Efforts Relating to Endangered Species Habitats Along the Central Platte River, Nebraska provides funding and an administrative structure to allow the states and the federal government to work together in enhancing water and land resources for endangered species. The agreement has two main objectives: 1. To develop and implement a recovery implementation program to improve and conserve habitat for four threatened and endangered species: whooping crane, piping plover, least tern and pallid sturgeon. 2. To enable existing and new water uses in the Platte River Watershed to proceed without actions beyond the Program for the four species under the Endangered Species Act. This NebFact discusses the publication participation, proposed program, and committee structure of this cooperative agreement

NF05-631 Understanding Watersheds

Watersheds are dynamic and unique places. They are complex webs of natural resources, — soil, water, air, plants and animals. Together land and water make a watershed a whole system. This NebFacts covers what a watershed is, how it works, its functions, how human activities can alter watershed functions, and its management

EC98-787 Glossary of Ecosystem Terms

This extension circular contains ecosystem definitions from abiotic to wildlife refuge

EC02-725 Guide to Buffers in the Blue River Basin

Extension Circular 02-725 is a guide to buffers in the Blue River Basin

EC96-143 Pesticide Runoff and Water Quality in Nebraska

Nebraska\u27s natural resources provide its residents with an abundance of wildlife, recreation, and agricultural opportunities. Some of the state\u27s most important resources are its lakes, rivers and streams. These surface waters provide year-round habitat for aquatic and terrestrial wildlife, rest stops for migratory birds, and countless hours of enjoyment for outdoor enthusiasts. In addition, surface waters provide a source of drinking water for many Nebraska residents, and are vital for some farming and industrial operations. To better understand how surface waters become contaminated from pesticide runoff, the various factors and processes influencing runoff must be understood. With this understanding, pesticide applicators will be able to manage pesticides more efficiently and reduce the potential for surface water contamination