SIMS

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.