Abstract
Controlled drainage in drainage ditches in the agricultural landscape is a drainage management strategy that has both environmental benefits (nutrient reductions) and production benefits. Innovative drainage strategies of spatially orientated low-grade weirs show promise to significantly improve nutrient (e.g. nitrate-N) reductions by expanding the area available for biogeochemical transformations, as well as providing multiple sites for runoff retention and nutrient reduction.
Innovative drainage strategies, such as low-grade weirs will provide state and federal agencies (i.e. USDA-ARS, NRCS, NOAA), as well as numerous other stakeholders (i.e. Ducks Unlimited, Delta F.A.R.M., Delta Wildlife) new and additional strategies for effective nutrient reduction to downstream coastal ecosystems.
The overall objective of this proposal is to identify the contribution weirs, an innovative, cost effective drainage management technique plays in decreasing source nitrate-N concentrations and loads to downstream coastal ecosystems. This objective is achieved by assessing the effectiveness of weirs in reducing nitrate-N concentrations and loads, highlighting changes in hydrology in manipulated systems and characterizing soil redox conditions as a result of controlled drainage. These two sub-objectives will be implemented at three spatial scales (replicated ditch experiments, field scale pre and post amendment experiment, instrumented field systems).
The replicated ditch experiments as well the field scale pre- and post amendment experiment will have simulated storm events added to each drainage system. This allows complete control over input concentrations, loads, flow rates and provides the opportunity for mass balance and nitrate-N reduction percentages to be calculated. The instrumented field system will monitor natural field hydrological events (both baseflow and stormflow) to determine mass balances and nitrate-N reduction percentages.
This research proposal will effectively demonstrate how weirs can reduce nitrate-N to coastal ecosystems. A demonstration/education project in conjunction with the Natural Resources Enterprise Program at Newton MS, will provide a field scale project with which farmers, and interested stakeholder can view low-grade weirs and the how they are installed and monitored. Furthermore, this demonstration site will host information days for county extension agents where they will be given information concerning the benefits of low-grade weirs. The demonstration project will allow stakeholders to understand how the system works, question experts and view real-time data from the project site. This knowledge will lead to better strategies for preventing nutrient contamination from source agriculture to receiving coastal systems.
Objectives
- To identify the contribution an innovative, cost effective drainage management technique plays in decreasing source nitrate-N concentrations and loads to coastal ecosystems
- To determine the effectiveness of weirs in reducing nitrate-N concentrations and loads within agricultural drainage ditches
- To characterize the impact of weirs on soil redox conditions and indirectly denitrification
Methodology
The objectives 1 & 2 will be approached throughout the duration of 2 years through three different project foci.
For Year 1 of the project, there will be two project foci:
Project Focus 1: Replicated ditch experiments whereby weir vs. non-weir systems are compared against one another to determine the effectiveness in nitrate mitigation.
Project Focus 2: Field scale research, by instrumenting a system pre and post weir installation to monitor reductions in nitrate N with time.
For Year 2 of the project, there will be two project foci:
Project Focus 2: Field scale research, by instrumenting a system pre and post weir installation to monitor reductions in nitrate N with time. (Continued from year 1)
Project Focus 3: Simulated field amendment experiment where a field scale artificial ditch system are amended with nitrate-N pre and post weir implementation to distinguish differences in load and concentration mitigation
Nitrate-N and total N will be the nitrogen species evaluated, at concentration and load levels. Soil redox will be evaluated with manufactured and calibrated soil Eh probes nested at various soil depths (5, 10 and 15cm) and spatially gradated within the respective drainage ditches.
In year 1, the field scale research suggested in Project Focus 2 will be a single system monitored, through the 319h EPA funded project, while the replicated ditch experiments will have 3 weir, 3 non-weir and 2 control replicates. A simulated storm event will be generated within each replicated ditch, with known inflow concentrations and loads, and hourly outflow samples will be taken to determine mitigation potential. Natural field hydrological events will be monitored for Project Focus 2. Baseflow will be sampled on a monthly basis, while storm flow events will be monitored on an event-driven basis. Changes in storm- and baseflow hydrographs and water levels within each ditch system as a result of the installation of low-grade weirs will be recorded every 15 minutes with HOBO water level (Focus 1 &2) recorders. A HOBO will be placed above the surface water level as a reference calibration.
In year 2, for Project focus 3, a single artificial drainage ditch will serve as a pre-post weir implementation experiment. A simulated storm event will be generated within the ditch, with known inflow concentrations and loads, and hourly outflow samples will be taken to determine mitigation potential. This simulated storm event will take place in the ditch with no weirs and post weir installation. Outflow concentrations, and flow rates will be carefully monitored to determined differences between pre and post-implementation. Changes in storm- and baseflow hydrographs and water levels will be recorded every 15 minutes with HOBO water level recorders strategically placed within each ditch system (Focus 2 &3). A HOBO will be placed above the surface water level as a reference calibration.
Rationale
Major changes in both fishing regulations and in U.S. demographics and travel patterns are proving challenging for Orange Beach fishing fleet. This multi-million dollar industry not only represents an important economic sector, but is also a vital link to the area’s cultural identity. The combination of circumstances creating today’s economic and regulatory conditions is threatening the industry’s future and the livelihoods of those it employs and supports.
Having a baseline of demographic and psychographic data on the current charter fishing customer will provide a crucial step in the ensuring the economic sustainability of this sector of the recreational fishing industry. Identifying customer characteristics and attitudes will assist in reaching more customers and expanding the market. Additionally, an estimation of the economic impact of this sector would prove extremely valuable in quantifying its overall contribution to the region and the state.
For More Information Contact: the MASGC Research Coordinator, Loretta Leist (Loretta.leist@usm.edu).
Please reference the project number R/CCD-19.