Cal-SIMETAW

Cal-SIMETAW (California Simulation of Evapotranspiration of Applied Water)

General Description	Estimates daily soil-water balance to determine potential crop ET and applied water ET for 132 individual crops, 20 crop categories, and four non-crop land-use categories by DAU/county for use in California Water Plan. Model website at: https://water.ca.gov/Programs/Water-Use-And-Efficiency/Land-And-Water-Use/Agricultural-Water-Use-Models
Model Domain	Water use by crops in California
Developer	California Department of Water Resources
Hardware computing requirements	N/A. Computer power is dependent on area of analysis.
Code language	C# and Oracle Spatial Database
Original application	Developed from SIMETAW, for California for 20 crops, 4 non-crop land use classes and historical data. Designed to estimate daily soil-water balance to determine crop evapotranspiration, (ETc) and evapotranspiration of applied water ( ETAW) for California Water Plan updates.
Public/proprietary and cost	Public by request through DWR
Physically or empirically based	Empirical
Mathematical methods used	Reference evapotranspiration, ETo, is estimated by using the Hargreaves-Samani equation calibrated to regional Penman-Monteith equation-derived reference evapotranspiration, to account for spatial climate variability. Crop coefficients (Kc) most fo 120 crops is developed in California using empirical data for ETc/ETo (potential ET measured for the crop/reference ET for the region)
Input data requirements	Weather/climate data: PRISM (monthly) and NCDC (daily) ETo: Spatial CIMIS correction for PRISM data Land cover (e.g. LandIQ, or DWR land use surveys) Crop coefficients (Kc) Soil characteristics (e.g. SSURGO) – water holding capacity, soil depth Irrigation schedules – can be developed assuming minimal water stress and 100% application efficiency Geographic DAU/County boundaries
Outputs	Format: Oracle database files. Various temporal scales (daily, monthly, yearly). Climate and calculated ETo data by PRISM grid (latitude and longitude) and DAU/county over the entire state. Daily soil water balance output by unit for individual crops and 20 crop categories by DAU/county. Monthly total ETo, ETc, Ep, ETaw, and AW by unit for individual crops and 20 crop categories by DAU/county. Seasonal and annual ETc, Ep, ETaw, and AW by unit for 20 crop categories by DAU/county within DAUs, counties, planning areas (PAs), hydrologic regions (HR), and region offices (ROs). Seasonal ETc, Ep, ETaw, and AW by volume for 20 crop categories by DAU/county, DAU, County, PA, HR, and RO. Volume values of seasonal and annual ETc, Ep, ETaw, and AW for 20 crop categories by DAU/county, DAU, County, PA, HR, and RO for a specific water year and calendar year.
Pre-processing and post-processing tools	N/A
Representation of uncertainty	Model verification vs. CIMIS (R = 0.98), no measure of error and several major assumptions required to run the data. No correction for runoff on the sites. Assumption that rainfall cannot exceed soil water depletion. Uncertain results for longer timescales (currently run on a daily scale).
Prevalence	Primarily used for California Water Plan updates every 5 years. ETAW and AW data is also used as inputs for irrigated agriculture models (e.g. SWAP, DAP).
Ease of use for public entities	Requires access to additional data sources (land cover) which can add additional costs to running the model. Requires GIS and coding capabilities to synthesize datasets and run models
Ease of obtaining information and availability of technical support	Direct contacts for developers available through DWR, technical manuals and model schematics not available online. No help desk or active working group advertised.
Source code availability	Not immediately downloadable, but accessible through program in C#
Status of model development	Completed and used for Water Updates every 5 years (DWR). No announcements on new directions/upgrades.
Challenges for integration	Requires some detailed information of irrigation for crop types. Constrained number of crop groups. Output can only be generated for DAUs and county level, not spatially explicit.

References:
Medellín-Azuara, J., & Howitt, R. E. (2013). Comparing Consumptive Agricultural Water Use in the Sacramento - San Joaquin Delta. Davis, CA.

Orang, M. N., Snyder, R. L., Hart, Q., Sarreshteh, S., & Eching, S. (2018). A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta - Appendix C. CalSIMETAW (California Simulation of Evapotranspiration of Applied Water). Davis, CA.

Orang, M. N., Snyder, R. L., Shu, G., Hart, Q. J., Sarreshteh, S., Falk, M., Eching, S. (2013). California Simulation of Evapotranspiration of Applied Water and Agricultural Energy Use in California. Journal of Integrative Agriculture, 12(8), 1371–1388. https://doi.org/10.1016/S2095-3119(13)60742-X

Rayej, M., Snyder, R. L., Orang, M. N., Geng, S., & Sarreshteh, S. (2011). CalSIMETAW and WEAP Models for Water Demand Planning. ICID 21st International Congress on Irrigation and Drainag ICID Transactions No.30-A, 111–128.