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DAP (Delta Agricultural Production Model)

General Description

Based on the SWAP (http://swap.ucdavis.edu) model, DAP is used to model agricultural land models agricultural crop production 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.
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://swapdap.ucdavis.edu 

Model Domain

Agricultural Crop agricultural economics economics of the Delta

Developer

Howitt and Medellin-Azuara (UC Davis) based on the SWAP model

Hardware computing requirementsNot specified

Runs in MS Windows environment.

Code language

Generalized Algebraic Modeling System (GAMS)

Original application

Developed for use in PPIC 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

(brackets include example datasets) Input data requirements include (source datasets are identified in parentheses):

  • Salinity data (monitoring station data from DWRoutsourced from hydrodynamic models including RMA)
  • Land Useuse
  • Crop prices
  • Crop Yieldsyields
  • 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

  • Allocation of acreage per crop type
  • Economic valueProduction 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 program applications through UC Davis in addition to DAP algorithmsCenter 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 developmentSeveral iterations use different disaggregation units, or additional areas of the Central Valley.

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.