| Popis: |
Lake Erie, among other inland waters, faces persistent threats from harmful algal blooms and hypoxia. The Western Lake Erie Basin (WLEB) algal bloom has especially been impacted by agricultural practices within its watershed; including the increased amount of surface field drainage in the heavy clays of the Paulding Plains. These shallow field ditches, 6 m wide, 0.5 m deep, and at least 100 m long, are too small to qualify under NRCS Conservation Practice Standard 412 for Grassed Waterways. Shallow field ditches are traditionally left unvegetated throughout the year, though sometimes grain crops are planted through them during growing season. It is hypothesized that these non-vegetated shallow field ditches are contributing statistically significant amounts of ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), dissolved reactive phosphorus (DRP), total nitrogen (TN), total phosphorus (TP), and sediment to their respective sub-watersheds within the Maumee River watershed, the foremost contributor to WLEB.This thesis describes and assesses the effectiveness of an edge-of-field water quality monitoring strategy for surface runoff implemented at three paired sites in the Paulding Plains region. Each field location had a non-vegetated and vegetated shallow field ditch pair, each shallow field ditch was instrumented with an edge-of-field monitoring set-up. The vegetation comprised of Kentucky bluegrass, Kentucky 31 fescues, and perennial ryegrass mixture. Monitoring at the outlet of each shallow fieldiiiditch was conducted with a cutthroat flume and ISCO sampler programmed to water sample precipitation event discharges. The effectiveness of the edge-of-field surface runoff monitoring was assessed by investigating precipitation adjustment errors and the causes of researcher, instrument, no runoff, and negligible runoff errors at each site in the observed runoff and water sample collection data. Assessment of the edge-of-field set-up was also completed regarding the durability of equipment and entire instrumentation for a four-year data collection time period. Specific suggestions were made in the discussion sections for each field location, but in general it was concluded site visit frequency should increase to bi-weekly and that the monitoring set-up used was durable and effective at capturing high flow runoff events with a constructed flume outlet fall of minimum 0.15 meters (0.5 feet). To better capture low flow events in future work, a plastic runoff collection receptacle should be attached at the flume outflow and the sample intake relocated to this receptacle.A thorough assessment of the effectiveness of vegetated shallow field ditches, in reducing sediment and nutrient runoff, requires multiple years of year-round data collection. Consistent water quality data collection began in February at one paired site and April at the other two paired sites, encompassing Spring, Summer, and part of Fall 2016. Chemical analyses were completed for the Spring and Summer water samples and preliminary statistical analyses of these results are included at the end of this thesis using one-way t-tests and Wilcoxon Signed-Rank tests, a=0.05 for both. Water samples were analyzed for NH4-N, NO3-N, DRP, TN, TP, and sediment. According to preliminary data, there were no reliable statistically significant results. However trends wereivobserved in the difference between the vegetated and non-vegetated shallow field ditch loading means for NH4-N and DRP. NH4-N had higher loading in non-vegetated shallow field ditches, indicating vegetated shallow field ditches lowering loading. DRP had no higher loading in non-vegetated shallow field ditches, indicating vegetated shallow field ditches have no decreasing effect on loading. General decreases in nutrients and sediment loadings means were observable in the data for vegetated shallow field ditches in comparison to non-vegetated counterparts. Water sample collection should continue year-round for two more years to determine if other data trends exist. |
