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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 website is at:  http://swap.ucdavis.edu

Model Domain

Agricultural 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 Public Policy Institute of California 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 (example source datasets are identified in parentheses):

• Salinity data (monitoring station data from DWRoutsourced 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)
• Elasticities (Russo et al. 2008)

Outputs

Outputs for 71 regions in the Sacramento San Joaquin Delta

• Allocation of acreage per crop typeInput use (land, water, labor and supplies) by region of analysis and crop group.
• Economic value

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 algorithmsCenter for Watershed Sciences.

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 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.

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.