DAP (Delta Agricultural Production Model)
General Description | Based on SWAP, DAP is used to model agricultural land and water use and economic performance but unlike SWAP, DAP disaggregates by agricultural islands and includes the effects of salinity in the water supply on crop yields. |
Model Domain | Agricultural economics of the Delta |
Developer | Howitt and Medellin-Azuara (UC Davis) based on SWAP model |
Hardware computing requirements | Not specified |
Code language | GAMS |
Original application | Developed for use in PPIC report "Envisioning Futures for the Sacramento-San Joaquin Delta" (Lund et al., 2007). |
Public/proprietary and cost | Based on SWAP model, modifications to algorithms available in Lund et al. (2007), runs on GAMS. |
Physically or empirically based | Empirical |
Mathematical methods used | Expansion of SWAP methods, which use positive mathematical programming (PMP) (Howitt, 1995). Salinity response in DAP is based on the Van Genuchten & Hoffman (1985) inverse sigmoid yield response function. |
Input data requirements | Input data requirements include: (brackets include example datasets)
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Outputs | Outputs for 71 regions in the Sacramento San Joaquin Delta
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Pre-processing and post-processing tools | None specified |
Representation of uncertainty | None specified |
Prevalence | Used in policy analysis by both academic, private consultants, and state agencies |
Ease of use for public entities | Requires knowledge of GAMS software, economic optimization and production economics theory, and access to program through UC Davis in addition to DAP algorithms. |
Ease of obtaining information and availability of technical support | Manuals or information on technical model beyond policy publications runs is not currently available. |
Source code availability | None |
Status of model development | Several iterations use different disaggregation units, or additional areas of the Central Valley. |
Challenges for integration | Similar to those of SWAP, however , DAP is also disaggregated into 71 smaller regions of the Delta. Model output scale map not match outputs of other models. |
References:
Howitt, R. (1995). A calibration method for agricultural economic production models. Journal of Agricultural Economics, 46(2), 147–159. https://doi.org/10.1111/j.1477-9552.1995.tb00762.x
Howitt, R. E., Macewan, D., Medellín-Azuara, J., & Lund, J. R. (2010). Economic Modeling of Agriculture and Water in California using the Statewide Agricultural Production Model. California Water Plan Update 2009, 4, 1–25.
Lund, J., Hanak, E., Fleenor, W., Howitt, R., Mount, J., & Moyle, P. (2007). Envisioning Futures for the Sacramento-San Joaquin Delta. Public Policy Institute of California. San Francisco, CA. https://doi.org/10.1007/s13398-014-0173-7.2
Medellin-Azuara, J. M., Howitt, R. E., Lund, J. R., & Fleenor, W. E. (2008). The Economic Effects on Agriculture of Water Export Salinity South of the Delta: Technical Appendix I. Comparing Futures for the Sacramento-San Joaquin Delta.
Medellín-Azuara, J., Hanak, E., Howitt, R., Lund, J., Ferrell, M., Kramer, K., … Stryjewski, E. (2012). Transitions for the Delta Economy Appendix A: Estimates of Acreage and Land Use. Public Policy Institute of California. San Francisco, CA.
Medellín–Azuara, J., Howitt, R. E., Hanak, E., Lund, J. R., & Fleenor, W. (2014). Agricultural Losses from Salinity in California's Sacramento-San Joaquin Delta. San Francisco Estuary and Watershed Science, 12(1), 1–16.
Van Genuchten, M., and G. Hoffman. 1985. "Analysis of Crop Salt Tolerance Data." In Soil Salinity under Irrigation, Processes and Management, ed. Shainberg, I., and J. Shalhevet (Berlin: Springer: Ecological Studies), 258–71.