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On-farm irrigation reservoirs, together with tailwater recovery systems, are commonly used to store water in the Mississippi River Valley alluvial floodplain to supplement limited groundwater resources. The inner slopes of the earthen embankments that enclose these reservoirs are subjected to continuous erosion due to wind-generated waves. Various methods have been used to protect the embankments, but none of them have been shown to be both sustainable and cost-effective. In an effort to assess levee protection strategies, a range of treatment techniques, including levee configurations and surface treatments, were applied on the embankments of the University of Arkansas Pine Bluff (UAPB) Lonoke Demonstration Reservoir in 2007. The treatment techniques included 17 different slope configurations along the east and west embankments and five chemical and mechanical treatments along the north and south embankments. Embankment erosion was measured by comparing new surveys conducted in 2015 and 2017 with as-built information provided by the USDA Natural Resources Conservation Service (NRCS). The change in levee profile between the surveys and the as-built profiles was used to quantify the effectiveness of the treatment methods for protection against wave action. An artificial neural network (ANN) prediction model was developed to establish relationships between erosion parameters (eroded area and maximum retreat) and four independent variables (existence of berm, face slope, maximum effective fetch, and probability of wind speed). Data from 27 sections were used for training, and data from seven sections were used for testing. Almost all of the slope treatments were significantly eroded over the eight to ten years that elapsed between construction and the surveys. Although having a berm did not significantly reduce the total eroded volume, in most cases it delayed the bank retreat. For any two identical slope configurations, the one with the longest fetch typically had at least slightly higher erosion and retreat. In general, milder slopes performed better than steeper slopes. The survey results showed that geo-synthetic fabric, fly ash, and soil cement were more effective at reducing wave erosion than the other treatment methods. [ABSTRACT FROM AUTHOR]

Increasing agricultural demands on limited groundwater resources in the Arkansas and Mississippi alluvial floodplain have created a growing need for the development of surface water resources. On-farm irrigation reservoirs are used to reduce dependence on groundwater supplies, but wind-induced wave erosion of levees creates an additional maintenance cost for producers. Measurements of levee erosion in a typical irrigation reservoir in east-central Arkansas were made with a ground-based LIDAR system and used to quantify erosion and estimate maintenance costs for irrigation reservoir levees. Approximately 1350 m³ of soil loss was measured from a 1530 m long levee during a seven-month period between December 2012 and July 2013. The damage was most severe in the northeast corner, where over 3 m of width were lost due to prevailing southerly winds blowing across the longest diagonal fetch length. Based on a typical cost (in 2014) for earth moving of $2.6 m-3, the cost to repair this loss would be approximately $3,500, resulting in a five-year maintenance cost of $17,500, which is about 16% of the initial cost of the levee. This research provides a basis for decision- making for producers who rely on irrigation reservoirs. Maintenance costs can be projected for a worst-casescenario of levee erosion, and the cost of protection can be balanced against expected erosion and repair costs. [ABSTRACT FROM AUTHOR]

The earthen levees commonly used to form irrigation reservoirs are subjected to significant embankment erosion due to wind-generated waves. The design of bank protection measures relies on adequate prediction of wave characteristics based on wind conditions and fetch length. Current formulations are based primarily on winds and waves in large water bodies and do not provide an optimal fit to waves in small water bodies such as irrigation ponds. Based on wind and wave data collected in an irrigation reservoir near Carlisle, Arkansas, the coefficients in a commonly used equation for wind wave prediction were improved for use in irrigation reservoirs. Details of the development of the new coefficients as well as data collection procedures are presented here. With the new empirical coefficients, the RMS error is 0.01 m for energy-based significant wave height and 0.06 s for peak wave period. [ABSTRACT FROM AUTHOR]

The earth levees commonly used for irrigation reservoirs are subjected to significant embankment erosion due to wind-generated waves. Large seasonal fluctuations in water level make vegetative bank protection impractical, and other stabilization methods, such as the use of stone or discarded tires, are not acceptable due to ecological or economic concerns. Here, a floating wave barrier made of polyethylene irrigation tubing is designed through a laboratory model study and subjected to a short-term prototype-scale field test. Based on wave characteristics measured in an irrigation pond near Carlisle, Arkansas, a laboratory-scale wave generating flume was designed, constructed, and used to test multiple wave barrier configurations for regular waves in deep and transitional water depths. Wave transmission characteristics were investigated for the following breakwater arrangements: (1) fully restrained, (2) vertically restrained with a single mooring line, and (3) horizontally restrained with piles at both sides of the wave barrier. The test results show that cylindrical pipes can be used effectively and that wave transmission characteristics strongly depend on the draft and mooring configuration of the wave barrier. The use of multiple small cylinders to replace a single large one is validated. A composite design made of two sizes of cylinders joined at the top was chosen for field testing. In the prototype-scale field test, wave amplitudes were reduced by an average of approximately 50%, which translates into a 75% reduction in wave energy. [ABSTRACT FROM AUTHOR]

Many sampling projects have been initiated or modified in recent years to quantify the effects of water quality protection and enhancement programs. Although comprehensive references on the theory and procedures related to discharge data collection have been published, similar guides to water quality sampling are not available. Several sources provide general guidance on sampling project design and on manual sampling procedures, but only recently has detailed information on automated storm water quality sampling been developed. As a result, a compilation of available information on the design of water quality sampling projects is needed to support sound decision-making regarding data collection resources and procedural alternatives. Thus, the objective of this article is to compile and present practical guidance for collection of discharge and water quality constituent data at the field and small watershed scale. The guidelines included are meant to increase the likelihood of project success, specifically accurate characterization of water quality within project resource constraints. Although many considerations are involved in establishing a successful sampling project, the following recommendations are generally applicable to field and small watershed studies: (1) consider wet-weather access, travel time, equipment costs, and sample collection method in the selection of sampling site numbers and locations; (2) commit adequate resources for equipment maintenance and repair; (3) assemble a well-trained, on-call field staff able to make frequent site visits; (4) establish reliable stage-discharge relationships for accurate discharge measurement; (5) use periodic manual grab sample collection with adequate frequency to characterize baseflow water quality; (6) use flow-interval or time-interval storm sampling with adequate frequency to characterize storm water quality; and (7) use composite sampling to manage sample numbers without substantial increases in uncertainty. [ABSTRACT FROM AUTHOR]