Alternative environmental benefits of agricultural drainage ditches

Abstract

Agricultural drainage ditches have received mixed reviews pertaining to their influence, role, and definition within the agricultural ecosystem. In the early part of the 20th Century, drainage ditches were viewed as a positive means to reduce mosquitoinfested wetlands and convert them into valuable agricultural production acreage (GRUMBLES 1991). In recent decades, however, there has been a concerted effort to attain a 'no net loss' of wetland acreage. This has placed drainage ditches in a precarious situation. They are needed to maintain field drainage, yet frequently their own characteristics may identify them as being wetlands themselves. Many drainage ditches possess the three macrofeatures of any wetland: hydroperiod, hydrosoil, and hydrophytes. There is, however, a fundamental difference in how agricultural drainage ditches are defined. For the purpose of the present study, drainage ditches are limited to those structures created to drain production acreage not marginal wetlands. Within the agricultural community, drainage ditches have been viewed as conduits for removing water from production acreage. The public perception has generally been negative in recent years, because constructed ditches have replaced natural drainage systems. Drainage ditches have largely been ignored in scientific research. Research from the Netherlands has focused on drainage ditch maintenance issues (VAN STRIEN et al. 1989, 1991), while DREN! & KERSTINU (1992) reported the use of experimental drainage ditches for ecotoxicological evaluations. Until now, little information has been available on the potential mitigation capabilities of drainage ditches. By viewing drainage ditches as buffers between production acreage and downstream aquatic receiving systems, it is possible to increase the water quality of agricultural runoff following storm events. Therefore, ditches may serve as an alternative best management practice (BMP). Historical BMPs related to agricultural land include, but are not limited to, winter cover crops, stiff grass hedges, riparian zones, grass filter strips, constructed wetlands, and conservation tillage. Most BMP research has been performed in the capacity of reducing sediment and nutrient-laden agricultural runoff (BurlElt et al. 1974, HAYES & HAIIs ION 1983, HAYES et al. 1984,