DETAW (Delta Evapotranspiration of Applied Water)
General Description | A tool for estimating evapotranspiration of applied water (ETaw), which is a seasonal estimate of the water requirement for evapotranspiration of a crop minus any water supplied by effective rainfall. ETaw information is needed to determine the demand side of water requirements. The model accounts for ET losses and water contributions from rainfall, seepage, irrigation, and using datasets with a daily time step. Model website at: https://water.ca.gov/Library/Modeling-and-Analysis/Bay-Delta-models-and-tools/DETAW |
Model Domain | Consumptive use and net channel depletion in the Delta |
Developer | California Department of Water Resources |
Hardware computing requirements | 1. Windows system |
Code language | V1.0 C++ (no longer available) |
Original application | Developed by DWR to replace the Delta Island Consumptive Use Model (DICU) and reconcile two water simulation models used by DWR (namely Calsim II and DSM2) |
Public/proprietary and cost | Public, available for download. General Public License. |
Physically or empirically based | Empirical |
Mathematical methods used | Hargreaves Samani (HS) equation, the reference evapotranspiration (ETo) at the CIMIS Lodi station was calculated; and by using the Penman-Monteith (PM) equation from nine CIMIS stations, including Lodi, isolines of correction factors to estimate Delta subareas ETo from the Lodi HS ETo were developed. Crop coefficients developed using SEBAL-based approach. |
Input data requirements | All input are already formatted csv files. Easily updated with public data described in the user manual.
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Outputs | HEC .dss (Data Storage Systems) – 1 daily, 1 monthly 168 subareas in 15 land use categories |
Pre-processing and post-processing tools | Several input calaculated using ArcGIS, but they can be used as-is in the model. HEC-DSSVue program required to view output files. |
Representation of uncertainty | ET results calibrated against other successful empirical ET models (SEBAL) (<3% difference) |
Prevalence | Internal to DWR but used for academic comparison and as a component of other models |
Ease of use for public entities | Package downloadable on the internet, all software required is open access. |
Ease of obtaining information and availability of technical support | User manual for V1.0 and V2.0 available with software download containing instruction for installation and model inputs/outputs. Email contact for DETAW available online. |
Source code availability | Available and freely modifiable under the General Public License |
Status of model development | Beta version 2.0 released June 2018. V 2.0 updates: updated seepage assumptions; calibrated crop coefficients based on satellite image-based estimates of consumptive use; estimated actual net channel depletion by estimating island diversions, seepages, and drainages; and assigned island diversions, seepages, and returns to model nodes |
Challenges for integration | Spatially explicit model requires model of nodes and spatial impacts of channels within each subarea (Liang & Suits 2017 pg. 3-11). Outputs for predetermined subareas (Liang & Suits 2017, fig. 3-2). |
References
Kadir, T., & Liang, L. (2018). A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta - Appendix D. Delta Evapotranspiration of Applied Water (DETAW). Davis, CA.
Liang, L., & Suits, B. (2017). Implementing DETAW in Modeling Hydrodynamics and Water Quality in the Sacramento-San Joaquin Delta. In Methodology for Flow and Salinity Estimates in the Sacramento-San Joaquin Delta and Suisun Marsh: 38th Annual Progress Report (p. 26). Department of Water Resources.
Medellín-Azuara, J., & Howitt, R. E. (2013). Comparing Consumptive Agricultural Water Use in the Sacramento - San Joaquin Delta. Davis, CA.
Figure source: Liang & Suits (2017)