|Constructed Wetlands to Prevent Adverse Effects of Cropland Runoff: A Modeling and Empirical Approach
Many studies have documented abilities of natural wetlands to filter and trap pollutants. Unfortunately these valuable wetland resources are often located in fertile stream and river corridors and through the years have been drained and converted to economically productive farmland. The long term cost of this "wetland to field" conversion is increased pollutant loading and damage to waterways and downstream areas. Recognition of these problems and their causes led to research and development of artificial or "constructed" wetlands. Constructed wetlands quickly found application as efficient, cost-effective replacements for conventional wastewater treatment facilities in financially limited small towns and cities. Lagoons and constructed wetlands were next successfully employed to clean heavily polluted runoff leaving feedlot, dairy, and industrial operations and have contributed to significant improvements in surface water quality. These point sources of pollution are relatively easy to identify and correct. More difficult are the non-point sources. Non-point source pollutants tend to have a longer pathway before detection and are therefore more likely to find their way into aquifers and other critical sources of drinking water. Identified pollutants in aquifers and surface waters point to the need for improved best management practices (BMPs) in contaminant application and filtering/processing in runoff. Water resource damage can be limited by using BMPs and installing constructed wetlands to control agricultural runoff. Size and design of these wetlands is more difficult to determine due to the wide variety of environmental conditions from farm to farm. Acreage, soil type, slope, rainfall, and soil and crop amendments all must be considered. To this end, Dr. Charles Cooper of the National Sedimentation Laboratory, in cooperation with Dr. Matt Moore and Dr. John Rodgers signed a project agreement with the Wetland Science Institute of the Natural Resources Conservation Service. Project goals were to (1) mathematically model fate of pesticides in herbaceous wetlands and (2) determine wetland size and design requirements using various inputs through mesocosm experiments.
The pesticide fate and wetland design models have been completed and are pending publication. If you would like more information concerning this research, contact Dr. Matt Moore.