DAP

DAP (Delta Agricultural Production Model)

General Description	Based on the SWAP (http://swap.ucdavis.edu) model, DAP models agricultural crop production and water use for a selection of islands in the Delta and incorporates crop yield response to salinity from root zone which is linked to irrigation water supply and drainage. Model website is at: http://dap.ucdavis.edu
Model Domain	Crop agricultural economics economics of the Delta
Developer	Howitt and Medellin-Azuara (UC Davis) based on the SWAP model
Hardware computing requirements	Runs in MS Windows environment.
Code language	Generalized Algebraic Modeling System (GAMS)
Original application	Developed for use in Public Policy Institute of California report "Envisioning Futures for the Sacramento-San Joaquin Delta" (Lund et al., 2007). Peer review publication is in Medellin-Azuara et al. (2014)
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 (source datasets are identified in parentheses): Salinity data (outsourced from hydrodynamic models including RMA) Land use Crop prices Crop yields Interest rates Land costs Supply costs Labor costs Surface water costs (USBR/DWR/water districts) Irrigation water (DWR) Available water (CVPM/DWR/USBR/water district, simulation models) Elasticities (Russo et al. 2008)
Outputs	Outputs for 71 regions in the Sacramento San Joaquin Delta Production input use (land, water, labor and supplies) by region of analysis and crop group. Economic value (gross revenues from crop farming)
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 applications through UC Davis Center for Watershed Sciences or UC Merced Water Systems Management Group (Medellin-Azuara).
Ease of obtaining information and availability of technical support	Manuals or information on technical model beyond policy publications model runs is not currently available.
Source code availability	None
Status of model development	Model continues to be updated with new land, water use and cost information through the UC Merced Water Systems Management group and the UC Davis Center for Watershed Sciences
Challenges for integration	Similar to those of SWAP, however DAP is also disaggregated into 71 smaller regions of the Delta. Model output scale map might 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. https://doi.org/10.15447/sfews.2014v12iss1art3

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.