Research Project: Managing Water and Sediment Movement in Agricultural Watersheds

Location: Watershed Physical Processes Research

2019 Annual Report

Objectives
1. Develop new knowledge and methodologies to quantify soil detachment and sediment transport, transformation, storage, and delivery. (1a:) Determine functional relations among variables (i.e., rainfall, soil moisture, soil texture, bulk density, organic matter, vegetation) with soil erosion. (1b:) Quantify the surface and subsurface processes controlling erosion and depositional features. (1c:) Quantify the effects of mixed-particle sizes and bed forms on roughness and sediment transport. 2. Improve knowledge of processes controlling surface and groundwater movement in agricultural watersheds, and their associated quantification. (2a:) Removed per approved Ad-hoc approval July 2018. See approved post plan. (2b:) Assess the use and management of floodplain water bodies for providing ecosystem services in order to support their use as a sustainable source of water for agriculture. (2c:) Quantify the processes partitioning components of the water budget in upland catchments of the Lower Mississippi River Basin. 3. Translate research into technology to quantify and evaluate management effects on watershed physical processes. (3a:) Develop a GIS-based erosion prediction management system that facilitates database acquisition and input file development, output visualization, and supports multiple scales of focus, including: watersheds, farm fields, and streams. (3b:) Develop technologies and tools to evaluate the benefits of conservation practice plans within and among fields, streams, and watersheds. (3c:) Develop new computer model components to simulate non-uniform sediment transport and stream morphologic adjustment at subreach scales. 4. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the Midsouth region, use the Lower Mississippi River Basin LTAR site to improve the observational capabilities and data accessibility of the LTAR network and support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Midsouth region. Research and data collection are planned and implemented based on the LTAR site application and in accordance with the responsibilities outlined in the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects. (4a:) Develop the Lower Mississippi River Basin LTAR location addressing issues of long-term agroecosystem sustainability specific to the region, participating in the Shared Research Strategy, and contributing to network-wide monitoring and experimentation goals. (4b:) Enhance the LMRB CEAP watershed long-term data sets and integrate with other long-term data sets in the LMRB to address agroecosystem sustainability at the basin scale. 5. Increase knowledge and understanding of the processes governing movement, storage, and quality of water in the Mississippi River Valley Alluvial Aquifer, and develop technologies to enhance the sustainability of water resources for agriculture. (5a:) and (5b:) See approved post plan.

Approach
In the Lower Mississippi River Valley, groundwater extraction for irrigation has outpaced aquifer recharge, and precipitation is expected to fall in fewer, higher intensity events, thereby increasing runoff and stream peak discharges. This will impact erosion patterns and rates, destabilize streams with consequent loss of arable land, adversely impact ecosystem services, and reduce reservoir usability. These are not only regional but also national concerns. There is a critical need for improved understanding and quantification of the processes that control: the movement of water across the landscape; the detachment and transport of soil and sediment; and the morphologic adjustment of channels. This research will use an integrated approach to watershed management through the development and testing of innovative practices and computational models based on a scientific understanding of hydrogeomorphic processes at the test-plot, farm, watershed, and river-basin scales. Field and laboratory, short- and long-term experiments will be conducted to fill technology and knowledge gaps in USDA erosion models concerning: ephemeral gully and soil pipe erosion; transport of eroded sediments and of sediments introduced by reservoir sediment management actions; and stream system physical integrity. Findings will be used to develop new computer modeling components to optimize conservation measure design and placement for the RUSLE, AnnAGNPS, and CONCEPTS computer simulation models. Long-term monitoring combined with new field experiments will investigate the long-term sustainability of surface and groundwater resources in the Lower Mississippi River Valley.

Progress Report
Progress was made on all five objectives and their subobjectives, all of which fall under National Program (NP) 211. We developed a new laboratory soil erodibility testing method; the construction of the experimental facility is nearing completion. The field site flume retrofit and laboratory rainfall collection system to study gully erosion processes and control are underway. Instrumentation for the field site are being installed. The laboratory experiments on the impacts of soil pipeflow combined with surface runoff on headcut migration were completed and the first draft of the paper is written. The laboratory facilities and methods for measuring sediment transport capacity of soil pipes were developed and experiments were conducted on medium size sand. Additional experiments are planned for transport of very fine sand, silt, and mixtures of particle sizes. In the field, over 50 flow events have been sampled for pipeflow rate and sediment concentrations, and data analysis is underway. Plans are to complete the sampling by the end of this calendar year. Regarding the research on mixed sand and gravel transport, a manuscript concerning the results of the experimental series of the structural effects of gravel-sand beds on the transport of bed load sediment has been submitted, to a refereed journal. Experiments exploring the effect of antecedent flows on transport of gravel and sand under fluvial conditions have been completed and the data collected are being analyzed. Data involving the fall velocity of fine sediment has been collected on Goodwin Creek, and are currently being analyzed. A manuscript summarizing the observed trends in effective and dispersed grain sizes for fine sediment is being prepared. Dune topography and sediment transport data were combined in a study of sediment transport following a sudden drop in water depth and velocity. A manuscript on the results was accepted. The manuscript contains final results for the experiments, including a predictive model for changing sand transport that is based on estimates of the sand transport before and after a rapid decrease in flow strength. Monitoring of particle settling traps at 3 locations in Beasley Lake was continued during FY2019. A new design for compact sediment traps that work in shallow water was completed, and it is being tested alongside existing traps in Beasley Lake. We published results of monitoring sedimentation rate, along with a model for the observed intra-annual variability, in a peer-reviewed journal article. We still do not have the support of the USGS to install deep groundwater wells in the Goodwin Creek Experimental Watershed (GCEW). However, analysis of shallow perched water tables and pipeflow has been completed, a paper published, and analysis of hydrographs at multiple scale is underway. We made progress on further improving the USDA, ARS natural resources computer models AnnAGNPS, CONCEPTS, EphGEE and RUSLE2, including their integration. The topographic analysis tool supporting the AnnAGNPS program was successfully developed to identify and characterize drainage features of a watershed, including prairie potholes in the midcontinental United States. The computer source code of RUSLE2 has been transformed to 64-bit and successfully tested on a web platform, in both one-dimensional and two-dimensional versions. The integrated capabilities of AnnAGNPS to characterize and evaluate ephemeral gullies, riparian buffers and constructed wetlands, as well as sheet and rill erosion, were successfully tested on an ARS experimental watershed in Mississippi. This provides critical management tools to evaluate the most efficient combination of conservation practices applied within watershed systems needed in conservation management planning. A one-dimensional model of subsurface flow was developed for incorporation into RUSLE2 to predict the spatial soil water distribution and seepage in hillslopes. For the CONCEPTS channel evolution computer model, a conceptual model describing the geometric features of streambank protection measures was developed, which can be used to relate local scour to reach-scale sediment transport rates. Laboratory data on the sorting of mixed sand and gravel beds were used to improve the two-dimensional bed-surface dynamics component of TELEMAC2D. The TELEMAC2D model is being enhanced in collaboration with Electricity of France to assess river and reservoir sediment practices. We made progress in developing the Lower Mississippi River Basin (LMRB) LTAR site through participation in national network activities, the establishment of new flux tower sites, and further development of the Common Experiment design for the LMRB site. The Water Information Systems by KISTERS (WISKI) was procured to enhance the collection, management, and analysis of precipitation, runoff, and sediment concentration data from GCEW. We continued development of a novel pilot project for investigating managed aquifer recharge in the Mississippi Valley Alluvial Aquifer. Plans and specifications for the project have been completed and construction is expected to begin this fall for data collection in 2020. In collaboration with scientists at the U.S. Geological Survey, conducted geophysical mapping of the aquifer to update its hydrogeologic understanding for the purposes of enhancing modeling efforts and planning sustainable water use from the region.

Accomplishments
1. New bank stability assessment technology incorporates variability of bank-soil erosion-resistance. The erosion-resistance of stream bank soils can vary significantly in space and time. Current bank erosion prediction technology does not account for this variability, which makes it difficult to select appropriate soil erosion-resistance values when assessing bank erosion. ARS researchers in Oxford, Mississippi, developed a new stochastic analysis of expected bank erosion that uses the distribution of measured erosion-resistance parameters such as soil erodibility and shear strength, and incorporated the analysis in the widely used ARS Bank Stability and Toe Erosion Model (BSTEM). The new BSTEM version is able to determine the probability that certain bank retreat magnitudes are exceeded. This is crucial information when critical infrastructure is located near rivers and streams. As part of the $1.6 Billion American River Common Features Program, the new technology is currently being used by the U.S. Army Corps of Engineers, Sacramento District, to prioritize bank protection measures to prevent levee failure around the City of Sacramento, California.

2. Results and model for seasonal changes in sedimentation rate for Beasley Lake, Mississippi. Sediments deposited in natural lakes represent an archive that can be used to detect and quantify changes in watershed erosion rates caused by changing weather or implementation of soil conservation measures. Due to the unconsolidated state of recently deposited sediments and insufficient passage of time for decay of radioisotopes, typical radiometric methods are only able to resolve rates from approximately 10 years prior to the sampling date. These factors lead to uncertainty in recent sediment accumulation rates, making it difficult to resolve the effects of changes in watershed management on timescales relevant to resource managers. To address these shortcomings, sediment from traps installed in Beasley Lake, Mississippi, was collected at 2- to 3-month intervals for 3 years by ARS scientists in Oxford, Mississippi. The results showed a delay in sedimentation caused by seasonal temperature and algal community changes, which means that changes in sediment load in runoff from specific precipitation events may not be detectable in the winter or early spring. Our observations question previous estimates of oxbow lake sediment trapping efficiency, since winter and spring sediment loads may remain in suspension for extended periods of time, increasing the probability of export from lakes. Accurate measurements of sediment accumulation in lakes on short time-scales provide resource managers relationships between best management practices, loss of critical oxbow lake habitat, and trapping efficiency of sediment-associated pollutants.

3. Effects of filling gullies on soil quality. Globally, the main cause of soil degradation is gully erosion. Filling-in gullies by equipment operations like tillage or scraping with box blades degrades the soil for significant distances adjacent to the gully. ARS researchers in Oxford, Mississippi, quantified the impact of filling of gullies on crop yield and soil quality adjacent to a gully. Soil properties were measured and sampled every 7.6 m out to 37 m from each side of a gully along five transects perpendicular to the gully. The best indicators of soil physical quality were depth of topsoil, available water capacity, shear strength at the surface, and soil penetration resistance at both the surface and 5-cm soil depth. The soil physical quality indicators were dramatically changed by tillage following the five-year period of no till such that the relationship between soil quality and the soil properties was no longer appropriate. This work will guide future efforts to address the dynamic changes in soil quality following tillage as the soil reconsolidates as well as the inclusion of chemical and biological properties to better assess the loss of soil quality due to gully filling.

4. Sunflower River point bar deposits contribute recharge to the Mississippi River Valley Alluvial Aquifer during periods of high flow. Surface-groundwater connections are an important pathway for recharging the Mississippi River Valley Alluvial Aquifer. ARS researchers in Oxford, Mississippi, demonstrated a pathway between the Sunflower River and the aquifer that depends on the stage of the river in which high flow events enter coarse deposits in the river banks, which are in turn connected to the underlying aquifer. This work will be of use to water resources managers in the region for determining the potential impact of practices such as instream weirs and other in-channel management practices for increasing recharge.

5. Urban development can lead to accelerated soil erosion. Measuring and modeling erosional processes is challenging in ungauged watersheds, especially in developing countries where rapid urbanization complicates parameter identification, model structure, and where erosional features like gullies are important components of the sediment budget. A simulation model was used by ARS scientists in Oxford, Mississippi, to quantify the sediment budget in the Los Laureles Canyon watershed, a rapidly urbanizing watershed in Tijuana, Mexico. Suspended sediment concentration (SSC) collected at 10 different locations during one storm event correlated with modelled SSC at those locations, suggesting the model represented spatial variation in sediment production. Simulated gully erosion was shown to represent about 40-55% of hillslope sediment production and 50% of the total sediment yield, which was produced by only 23% of the watershed area that is on steep highly erodible marine sediments. The model identifies priority locations for installation of sediment control measures and can be used to identify tradeoffs between sediment control and runoff production. Scenario analysis for those locations would reduce total sediment yield by 30%, but may increase peak discharge moderately (2-21%) at the watershed scale.

6. Prediction of sand transport during rapid decreases in water discharge. The presence of relict bed forms in ephemeral streams reduces the accuracy of sediment transport predictions, impacting restoration efforts, flow stage prediction, flood forecasting, and validation of controls on sediment transport. In addition, the bottom topography of channels, which in sand beds often consists of dune-shaped bed forms that are affected by changes in flow rate, affects flow-depth, flooding, bank stability, and sediment transport rate, making it an essential component for sediment transport and flow modeling efforts. Previous research has shown that an equilibrium sand bed formed at a high flow rate followed by a rapid reduction in flow discharge and depth produced a gradual reduction in sediment load that could be modeled with a two-term exponential equation. Additional data from new experiments by ARS scientists in Oxford, Mississippi, generalized the relationship for predicting the decay in sand transport rate resulting from a rapid decrease in flow strength. The information can be used by river engineers and resource managers who need to be able to predict sediment transport during rapidly reduced flow conditions.

7. Effect of bed surface structure on the transport of coarse sediment in streams. Accurate knowledge of the movement of sediment in streams is necessary to assess the potential of the channel to transport and erode sediment, to assess the net rate of erosion for the upstream watershed, and to assess the stability of the channel boundary. Experiments were conducted in a laboratory channel by ARS scientists in Oxford, Mississippi, to determine the effect of flow strength on the structure of a sediment bed consisting of a mixture of sand and gravel. The structure of the channel bed was found to change with increasing flow strength such that sand corridors formed and evolved which affected sediment transport, bed roughness, and the depth of flow. An understanding and predictive capability for the evolution of the bed surface structure is important for improving the generally poor performance of sediment transport prediction methodologies. Information of this type will be useful to develop improved tools to predict bed material transport and the stability of channel boundaries. This capability will allow watershed managers to more effectively manage sediment in agricultural watersheds in an environmentally sensitive manner to facilitate the design and maintenance of stable channels and contribute to the preservation of soils and sustainable agriculture.

8. Complexity of Mississippi River Valley Alluvial Aquifer (MRVA) revealed through subsurface mapping. The MRVA is one of the most productive agricultural aquifers in the United States, supplying irrigation for 8 million acres of arable land, which results in approximately $9 billion in direct revenues annually for crops. Reliance on groundwater for irrigation has resulted in alarming declines in groundwater levels across the region. Using an airborne geophysical mapping survey, ARS researchers in Oxford, Mississippi, in collaboration with the U.S. Geological Survey have updated the basic understanding of the aquifer and its recharge sources. This mapping effort provided an unprecedented three-dimensional view of the entire aquifer structure thereby revealing deep structure such as paleochannels and preferential flow paths. This survey will provide a long-term foundation for hydrologic and geologic research in the region to support sustainable water resources.

Review Publications
Wilson, G.V., Wells, R.R., Dabney, S.M., Zhang, T. 2018. Filling an ephemeral gully channel: impacts on physical soil quality. Catena. 174:164-173. https://doi.org/10.1016/j.catena.2018.11.006.
Ozeren, Y., Wren, D.G., Yasarer, H. 2018. Assessment of levee treatments for an irrigation reservoir in Arkansas. Transactions of the ASABE. 61(5):1677-1689. https://doi.org/10.13031/trans.12983.
Wanger, M., Fox, G., Wilson, G.V., Nieber, J. 2019. Laboratory experiments on the removal of soil plugs during soil piping and internal erosion. Transactions of the ASABE. 62(1):83-93. https://doi.org/10.13031/trans.13092.
Mulatu, C.A., Crosato, A., Moges, M.M., Langendoen, E.J., McClain, M. 2018. Morphodynamic trends of the Ribb River, Ethiopia, prior to dam construction. Geosciences. 8(7):255. https://doi.org/10.3390/geosciences8070255.
Stover, J., Keller, E.A., Dudley, T.L., Langendoen, E.J. 2018. Fluvial geomorphology, root distribution, and tensile strength of the invasive giant reed, Arundo donax, and its role on stream bank stability in the Santa Clara River, southern California. Geosciences. 8(8):304. https://doi.org/10.3390/geosciences8080304.
Gudino-Elizondo, N., Biggs, T., Bingner, R.L., Yuan, Y., Langendoen, E.J., Taniguchi, K., Kretzschmar, T., Taguas, E.V., Liden, D. 2018. Modeling ephemeral gully erosion from unpaved roads: Equifinality and implications for scenario analysis. Geosciences. 8(4)137. https://doi.org/10.3390/geosciences8040137.
Wren, D.G., Rigby Jr, J.R., Langendoen, E.J., Kuhnle, R.A. 2018. Sampling interval analysis and CDF generation for grain-scale gravel bed topography. Journal of Hydraulic Engineering. 144(10). https://doi.org/10.1061/(ASCE)HY.1943-7900.0001522.
Wren, D.G., Taylor, J.M., Rigby Jr, J.R., Locke, M.A., Yasarer, L.M. 2019. Short term sediment accumulation rates reveal seasonal time lags between sediment delivery and deposition in an oxbow lake. Agriculture, Ecosystems and Environment. 281:92-99.
Wilson, G.V., Wells, R.R., Kuhnle, R.A., Fox, G.A., Nieber, J. 2018. Sediment detachment and transport processes associated with internal erosion of soil pipes. Earth Surface Processes and Landforms. 43:45-63.
Xu, X., Zheng, F., Wilson, G.V., Wu, M. 2017. Upslope inflow, hillslope gradient and rainfall intensity impacts on ephemeral gully erosion. Land Degradation and Development. 28(8):2623-2635. https://doi.org/10.1002/ldr.2825.
Hou, R., Zhu, O., Han, D., Wilson, G.V. 2018. Effects of field experimental warming on wheat root distribution under conventional tillage and no-tillage systems. Ecology and Evolution. 8(5):2418-2427. https://doi.org/10.1002/ece3.3864.
Akay, O., Ozer Tolga, Fox, G.A., Wilson, G.V. 2018. Application of fibrous streambank protection against groundwater seepage erosion. Journal of Hydrology. 565:27-38. https://doi.org/10.1016/j.jhydrol.2018.08.010.
Wren, D.G., Ozeren, Y., Taylor, J.M., Reba, M.L., Bowie, C. 2018. Assessment of irrigation reservoir levee impairment in Arkansas, USA. Journal of Soil and Water Conservation. 73(5):533-540. https://doi.org/10.2489/jswc.73.5.533.
Surbeck, C.Q., Davidson, G.R., Wren, D.G. 2018. Long-term metal and arsenic mobility between wetlands and lakes variable histories within the same floodplain. Applied Geochemistry. 96:244-251.
Momm, H.G., Bingner, R.L., Wells, R.R., Porter, W.S., Yasarer, L.M., Dabney, S.M. 2019. Enhanced field-scale characterization for watershed erosion assessments. Journal of Environmental Modeling and Software. 117:134-148. https://doi.org/10.1016/j.envsoft.2019.03.025.