Assessment of the Ecological Value of Low-Grade Weirs in Agricultural Drainage Ditches

Author(s): Poganski, B.; Kröger, R.

Agricultural best management practices have been a common fixture in farm field landscapes for decades. Unfortunately, little scientific information documents ecological and economic benefits of implementing such practices. Recent literature has highlighted the ability of low-grade weirs placed in agricultural drainage ditches to decrease sediment and nutrient loads to downstream waters by altering ditch discharge rates and hydraulic residence time. Currently, knowledge of how these structures can affect agricultural landscape ecology, from the molecular to ecosystem level, is unknown. The aim of this research is to assess the ecological value of low-grade weirs as effective management practices in agricultural drainage ditches. Ecological value will be appraised based on the diversity and richness of organisms inhabiting such systems. Organismal communities were selected for evaluation because of their critical roles in nutrient cycling and exchange within aquatic food webs. Experimental organisms include aquatic vegetation, microbes, benthic macroinvertebrates, and fish. Sampling events will be conducted during the growing season (May-June) annually for 3 years in agricultural drainage ditches fitted with low-grade weirs in the upper Yazoo River Basin. Conducting the experiment during the specified time period increases the likelihood that water will be present in ephemeral ditches. Organism data will be compared to chemical sediment and water data collected at the study sites provided by an ongoing study that will continue on a parallel temporal scale. Investigating biologically diverse but systematically linked organisms, will not only supplement estimates of the total ecological value of low-grade weirs in drainage ditches, but analysis of individual groups of organisms will aid in predicting mechanistic effects of implementing such structures in heavily cultivated agricultural landscapes.

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Technical Sessions

1 Best Management Practices #1
2 Delta Water Assessment
3 Flood Assessment & Mgmt.
4 Wetlands
5 Watershed Mgmt. #1
6 Non-Point Source Assessment
7 Modeling
8 Water Quality
9 Best Mgt. Practices #2
10 Delta Water Conservation
11 Sedimentation
12 Storm Water
13 Watershed Mgt. #2
14 Public Water Systems
15 Surface Water Assessment & Evaluation

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