SIMS (Satellite Irrigation Management Support System)

General Description	Originally developed to enhance the utility and accessibility of satellite data for irrigation management and scheduling. Relies on remote sensing data in the red and near-infrared wavelengths and reference evapotranspiration (ETo) data from the California Irrigation Management Information System (CIMIS) for calculation of basal crop evapotranspiration (ETcb). ETcb is preferable for irrigation scheduling since it represents the crop's biological water demand. Integrates NASA's TOPS, Landsat, MODIS, and CIMIS to calculate demand at a spatial resolution of 0.25 acres from 2010 to present. Model website at: https://ecocast.arc.nasa.gov/simsi/
Model Domain	Water use and demand of crops.
Developer	NASA-Ames Monterey
Hardware computing requirements	Beta web interface, python-based server
Code language	NA
Original application	Developed by NASA to enhance the utility and accessibility of satellite data for irrigation management and scheduling. TOPS-SIMIS application developed for direct use by farm operators.
Public/proprietary and cost	Free public data available through web interface. A web-based user interface providing access to visualizations of TOPS-SIMS information eliminates the barriers to data access, as only a web browser is needed to view and query the information, and no knowledge of specialized data formats is necessary.
Physically or empirically based	Empirical
Mathematical methods used	Model uses Top of Canopy or Top of Atmosphere reflectance to calculate the normalized difference vegetation index (NDVI) and fractional cover (Fc). SIMS then combines Fc with estimates of crop height and stomatal control to calculate the actual basal crop coefficient (Kcb_actual) for each 30m x 30m pixel. SIMS calculates the actual ETcb (ETcb_actual) following the FAO-56 approach (Allen et al., 1998) and multiplies Kcb_actual for each 30m x 30m pixel by the California Department of Water Resources Spatial CIMIS daily ETo.
Input data requirements	See attached figure: TOPS Landsat 7/8 Spatial CIMIS (water content, soil water potential, drainage, irrigation, precipitation, wind speed) Crop coefficients (Kc)
Outputs	CSV containing multi-year variables Can only direct download one coordinate at a time.
Pre-processing and post-processing tools	None specified
Representation of uncertainty	Field validation found that calculated ETcb was within +/-10% for well-watered crops, and within +/-15% for 15 major California crops.
Prevalence	Predominantly academic, but publically available
Ease of use for public entities	Easily accessible data through web interface, potential opportunity to connect with python back-end for download.
Ease of obtaining information and availability of technical support	Website contains basic help for navigating interface and dataset as well as links to research and scientific basis. Developer contact information readily available through website.
Source code availability	None
Status of model development	Ongoing work is incorporating data from Sentinel-2A to further increase the satellite observation frequency at the 20-30m spatial resolution. Participating growers will ultimately be able to create an account, draw or upload information to define a region of interest, and configure customized reports summarizing Kc and ETc values for fields or blocks of interest.
Challenges for integration	Web interface is a barrier to collecting large scale datasets for use with other models. Interface only allows query of one set of coordinates at a time, an API or alternate platform for the model would be needed.

References

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. FAO, Rome, 300(9).

Melton, F. S., Johnson, L. F., Lund, C. P., Pierce, L. L., Michaelis, A. R., Hiatt, S. H., Nemani, R. R. (2012). Satellite irrigation management support with the terrestrial observation and prediction system: A framework for integration of satellite and surface observations to support improvements in agricultural water resource management. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 5(6), 1709–1721. https://doi.org/10.1109/JSTARS.2012.2214474

Melton, F., Guzman, A., Johnson, L., Rosevelt, C., & Post, K. (2018). A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta - Appendix E. Appendix G. NASA Satellite Irrigation Management Support System (SIMS). Davis, CA. https://doi.org/10.1002/j.1681-4835.2014.tb00468.x

Figure 1 - Overview of TOPS-SIMS architecture with data inputs and outputs (Melton et al., 2012)

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