Assessment of irrigation reservoir levee impairment in Arkansas, United States

The use of surface water resources for irrigation in the state of Arkansas increased over the years following 2000 due to groundwater depletion. In order to reduce dependence on groundwater, irrigation reservoirs and tailwater recovery systems are used to capture and store water for irrigation. Irrigation reservoir levees are typically constructed from local soils that are often low in cohesion, and the use of rock armoring and geotextiles is limited due to high costs, resulting in levees that are susceptible to erosion. Wind-driven waves erode the exposed inner slopes of the levees, resulting in the need for frequent repairs, an added expense for agricultural producers. Evaluation of the status of irrigation storage reservoirs and identification of design factors that contribute to erosion are needed to address the problem. A survey was conducted in 2013 to 2015 to assess the current state of levee erosion and attempt to identify associated factors. It was found that 79% of the 584 homogeneous levee segments contained within 148 surveyed reservoirs had block failures and near-vertical slopes. Despite regional winds with preferential southerly and northerly directions, levees of all orientations were damaged by waves. For the surveyed irrigation reservoir levees, soil type, vegetation, inner slope, and berm presence were found to be poor predictors of the state of impairment. The most important variable associated with levee failure was maximum effective fetch length, such that longer fetches were more likely to have block failures and greater loss of top width.