Research Project: Sustaining Irrigated Agriculture in an Era of Increasing Water Scarcity and Reduced Water Quality

Location: Agricultural Water Efficiency and Salinity Research Unit

2018 Annual Report

Objectives
Objective 1: Evaluate the effects of degraded irrigation waters on crop water use and yield at commercial production scales. Subobjective 1A: Evaluate the impact of salinity on crop water use and productivity by observing evapotranspiration and carbon fluxes in commercial almond and pistachio orchards exhibiting a range of salinities. Subobjective 1B: Develop quantitative relationships between remotely-sensed plant canopy observations and measured crop water use and productivity. Objective 2: Develop an innovative, open informatics platform for disseminating information, tools, and recommendations for the management of marginal quality irrigation and artificial recharge waters. Subobjective 2A: Develop a web-based platform for disseminating information, tools, and recommendations for evaluating and managing saline irrigation waters. Subobjective 2B: Develop improved models to support managed aquifer recharge (MAR) treatment of alternative water resources for irrigation.

Approach
Drought, climate change, and competition for resources are reducing the availability of irrigation water and farmland in arid and semi-arid regions. One strategy for maintaining or enhancing productivity in the face of diminished resource availability is to make greater use of marginal lands and alternative water sources, both for irrigation and for recharging depleted aquifers. Sustainable use of low quality waters requires soil, water, and crop management practices that optimize crop production and aquifer recharge while minimizing the degradation of natural resources by salts and other contaminants. Advanced models and decision-support tools are needed to evaluate alternative management practices and to assist growers and water managers in satisfying increasingly stringent regulations. In this project, we use micro-meteorological methods to evaluate field-scale crop productivity and water-use across a network of research sites in commercial orchards exhibiting a range of soil salinities and irrigation water qualities. Additionally, we develop an open, web-based informatics platform for disseminating information, models, and decision-support for the use of saline irrigation waters. Lastly, we develop modeling tools focusing on two problems associated with alternative waters and managed aquifer recharge operations: (i.) decreasing infiltration due to soil clogging by colloids; and (ii.) infiltration depths and setback distances required to ensure microbial safety at groundwater extraction points. The project should lead to improved recommendations for managing alternative water resources for irrigation and recharge, and produce new capabilities for predicting the effects of management decisions on crop yields and on soil and water quality.

Progress Report
Objective 1: Monitoring and data collection continued at the five San Joaquin Valley, California field sites established in FY17 (Sub-objective 1A). The monitoring sites consist of eddy covariance (ECV) towers and instrumentation, plus soil monitoring instrumentation. Data workflows for processing the ECV data have been updated. A cooperating graduate student from University of California, Riverside, is incorporating the soil water content and electrical conductivity observations into modeling research. Analysis of field electrical conductivity surveys (Sub-objective 1B) from saline fields and other sites revealed that previously established soil salinity mapping approaches had great difficulty working in complex irrigation systems such as drip irrigation. New methodological surveying approaches are under development in conjunction with another scientist from ARS Riverside, California. Analysis of soil properties and irrigation distributions are largely complete. Objective 2: The focus is the development of informatics and modeling tools for salt-affected irrigated agricultural systems and for managed aquifer recharge operations. Under Sub-objective 2A, Fluxpart (version 0.1.0), a computer program that processes data from eddy covariance monitoring systems to determine water vapor and carbon dioxide fluxes in agricultural fields and other landscapes was released. Water and carbon dioxide flux data provide information about plant growth and water use that is essential in many kinds of agronomic and climate research, including our field work under Objective 1. Encouraged by positive feedback from early users, considerable effort was devoted toward developing Fluxpart version 0.2.0, which has significantly improved capabilities for handling large volumes of data (big data) and a refined flux partitioning algorithm. The updated code will be released in early FY19. The planned update of the RETC software package was completed. The RETC software is the industry standard for analyzing and modeling the water retention and hydraulic conductivity of properties of unsaturated soils. Work continued on applications for modeling and informatics tools. ARS scientists in Riverside, California, participated in a study with the University of California, Riverside, in which ARS hydrologic and agronomic systems models were employed in a hydro-economic analysis of Salton Sea inflows and worked with colleagues from the Swedish University of Agricultural Sciences, the Norwegian Institute for Agricultural and Environmental Research, and Rutgers University on x-ray imaging of soil macroporosity and modeling soil permeability. Sub-objective 2B: Considerable research was directed toward developing improved models to support Managed Aquifer Recharge (MAR) operations. A numerical model was developed to simulate storm water capture and enhanced aquifer recharge using modern drywell geometries that include a sediment chamber, an overflow pipe, and the variable geometry and storage of the drywell system with depth. Falling-head infiltration experiments were conducted on drywells located at the National Training Center in Fort Irwin, California, and a commercial complex in Torrance, California, to determine in situ soil hydraulic properties for an equivalent uniform soil profile by inverse parameter optimization. A good agreement between the observed and simulated water heights in drywells was obtained for both sites. Numerical experiments were conducted to determine the influence of subsurface heterogeneity on drywell infiltration performance. The presence of many highly permeable, laterally extending lenses was found to provide a larger surface area for enhanced infiltration than the presence of isolated, highly permeable pockets. These experiments and simulations provide useful information to improve the design and assess the performance of drywells for enhanced recharge, and to characterize in situ soil hydraulic properties. This research was partially supported by an interagency agreement with the Environmental Protection Agency, 2036-61000-018-03I, “Research Support for Watershed and Basin Hydrology”.

Accomplishments
1. “Fluxpart” software released for micrometeorological gas flux partitioning. The eddy covariance method is routinely used to measure gas fluxes over agricultural fields and other landscapes, providing essential data for many kinds of agronomic and climate research. However, greater insight into the functioning of agroecosystems is possible if the measured gas fluxes can be separated into their constitutive components; e.g., the water vapor flux into transpiration and direct evaporation components, and the carbon dioxide flux into photosynthesis and respiration components. ARS researchers in Riverside, California developed new mathematical results that facilitate partitioning analyses, and released new open source software that processes large volume data streams (big data) that implements the flux variance similarity partitioning algorithm. The research and software benefits scientists, engineers, and irrigators seeking to monitor, understand, and optimize water use in agroecosystems.

2. Impact of alternate wind speed data on irrigation parameterization. Meteorological data are frequently used to estimate crop evapotranspiration, which controls irrigation scheduling. However, wind speeds can be highly variable between weather stations, resulting in potentially inaccurate crop evapotranspiration calculations and poor irrigation. An ARS researcher at Riverside, California and collaborators from Federal University of the Semi-Arid, Brazil, assessed the impact of non-local wind speeds on irrigation parameterization and the potential improvement in irrigation parameterization using field-specific wind speed data to calculate irrigation needs. Results show that wind speeds are highly variable in coastal regions of California and that using the nearest meteorological station (as is common practice now) does not provide an adequate substitute for wind speed data. Adding an on-farm sonic anemometer that requires minimal farmer maintenance can result in an improvement in crop evapotranspiration parameterization of 5-10 percent, which could save farmers significant water costs in coastal California where farmers often must use expensive (more than $1,500/acre-foot) water sources.

Review Publications
Anderson, R.G., Zhang, X., Skaggs, T.H. 2018. Measurement and partitioning of evapotranspiration for application to vadose zone studies. Vadose Zone Journal. 16(13):1-9. doi:10.2136/vzj2017.08.0155.
Skaggs, T.H., Anderson, R.G., Alfieri, J.G., Scanlon, T.M., Kustas, W.P. 2018. Fluxpart: Open source software for partitioning carbon dioxide and water vapor fluxes. Agricultural and Forest Meteorology. 253:218-224. https://doi.org/10.1016/j.agrformet.2018.02.019.
Adrian, Y.F., Schneidewind, U., Bradford, S.A., Simunek, J., Fernandez-Steeger, T.M., Azzam, R. 2018. Transport and retention of surfactant- and polymer-stabilized engineered silver nanoparticles in silicate-dominated aquifer material. Environmental Pollution. 236:195-207. https://doi.org/10.1016/j.envpol.2018.01.011.
Sasidharan, S., Bradford, S.A., Simunek, J., Dejong, B., Kraemer, S. 2018. Evaluating drywells for stormwater management and enhanced aquifer recharge. Advances in Water Resources. 1116:167-177. https://doi.org/10.1016/j.advwatres.2018.04.003.
Sasidharan, S., Bradford, S.A., Simunek, J., Torkzaban, S., Vanderzalm, J. 2017. Transport and fate of viruses in sediment and stormwater from a managed aquifer recharge site. Journal of Hydrology. 555:724-735. https://doi.org/10.1016/j.jhydrol.2017.10.062.
Corwin, D.L., Yemoto, K.K., Clary, W., Banuelos, G.S., Skaggs, T.H., Lesch, S.M., Scudiero, E. 2017. Evaluating oilseed biofuel production feasibility in California's San Joaquin Valley using geophysical and remote sensing techniques. Sensors. 17(10):2343. https://doi.org/10.3390/s17102343.
Whitney, K., Scudiero, E., El-Askary, H.M., Skaggs, T.H., Allali, M., Corwin, D.L. 2018. Validating the use of MODIS time series for salinity assessment over agricultural soils in California, USA. Ecological Indicators. 93:889-898. https://doi.org/10.1016/j.ecolind.2018.05.069.
Anderson, R.G., Ferreira, J.F., Jenkins, D.L., da Silva Dias, N., Suarez, D.L. 2017. Incorporating field wind data to improve crop evapotranspiration parameterization in heterogeneous regions. Irrigation Science. 35(6):533-547. https://doi.org/10.1007/s00271-017-0560-x.
Sasidharan, S., Bradford, S.A., Simunek, J., Torkzaban, S. 2018. Minimizing virus transport in porous media by optimizing solid phase inactivation. Journal of Environmental Quality. doi:10.2134/jeq2018.01.0027.
Ashworth, D.J., Yates, S.R., Anderson, R.G., Van Wesenbeeck, I.J., Sangster, J.L., Ma, L. 2018. Replicated flux measurements of 1,3-dichloropropene from a bare soil under field conditions. Atmospheric Environment. 191:19-26. https://doi.org/10.1016/j.atmosenv.2018.07.049.