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User Guide for the Farm Process (FMP1) for the U.S. Geological Survey's Modular Three-Dimensional Finite-Difference Ground-Water Flow Model, MODFLOW-2000

By Wolfgang Schmid1, R.T. Hanson, Thomas Maddock III2, and S.A. Leake

1Research Hydrologist, Department of Hydrology and Water Resources, University of Arizona

2Professor amd Department Head, Department of Hydrology and Water Resources, University of Arizona



Techniques and Methods 6-A17

Sacramento, California 2006

Prepared by the U.S. Geological Survey, Office of Ground Water, Ground-Water Resources Program

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There is a need to estimate dynamically integrated supply-and-demand components of irrigated agriculture as part of the simulation of surface-water and ground-water flow. To meet this need, a computer program called the Farm Process (FMP1) was developed for the U.S. Geological Survey three-dimensional finite-difference modular ground-water flow model, MODFLOW- 2000 (MF2K). The FMP1 allows MF2K users to simulate conjunctive use of surface- and ground water for irrigated agriculture for historical and future simulations, water-rights issues and operational decisions, nondrought and drought scenarios. By dynamically integrating farm delivery requirement, surface- and ground-water delivery, as well as irrigation-return flow, the FMP1 allows for the estimation of supplemental well pumpage. While farm delivery requirement and irrigation return flow are simulated by the FMP1, the surface-water delivery to the farm can be simulated optionally by coupling the FMP1 with the Streamflow Routing Package (SFR1) and the farm well pumping can be simulated optionally by coupling the FMP1 to the Multi-Node Well (MNW) Package. In addition, semi-routed deliveries can be specified that are associated with points of diversion in the SFR1 stream network. Nonrouted surface-water deliveries can be specified independently of any stream network. The FMP1 maintains a dual mass balance of a farm budget and as part of the ground-water budget.

Irrigation demand, supply, and return flow are in part subject to head-dependent sources and sinks such as evapotranspiration from ground water and leakage between the conveyance system and the aquifer. Farm well discharge and farm net recharge are source/sink terms in the FMP1, which depend on transpiration uptake from ground water and other head dependent consumptive use components. For heads rising above the bottom of the root zone, the actual transpiration is taken to vary proportionally with the depth of the active root zone, which can be restricted by anoxia or wilting. Depths corresponding to anoxia- or wilting-related pressure heads within the root zone are found using analytical solutions of a vertical pseudo steady-state pressure- head distribution over the depth of the total root zone (Consumptive Use Concept 1). Alternatively, a simpler, conceptual model is available, which defines how consumptive use (CU) components vary with changing head (CU Concept 2).

Subtracting the ground water and precipitation transpiration components from the total transpiration yields a transpiratory irrigation requirement for each cell. The total farm delivery requirement (TFDR) then is determined as cumulative transpiratory and evaporative irrigation requirements of all farm cells and increased sufficiently to compensate for inefficient use from irrigation with respect to plant consumption. The TFDR subsequently is satisfied with surface- and ground-water delivery, respectively constrained by allotments, water rights, or maximum capacities.

Five economic and noneconomic drought response policies can be applied optionally, if the potential supply of surface water and ground water is insufficient to meet the crop demand: acreage-optimization with or without a water conservation pool, deficit irrigation with or without water-stacking, and zero policy.




Irrigation Water Demand and Supply

Previous Simulation of Crop Demand and Irrigation Water Supply

Modeling Agricultural Irrigation Supply and Demand

Purpose and Scope


Farm Process Capabilities

Consumptive Use

Transpiration for Water Levels between Ground Surface and Bottom of Root Zone

Consumptive-Use Concept 1

Consumptive-Use Concept 2

Transpiration for Water Levels between Bottom of the Root Zone and the Extinction Depth

Evaporation for Water Levels between Ground Surface and Extinction Depth

Head-Dependent Transpiration from Precipitation

Head-Dependent Crop Irrigation Requirement

Surface-Water Supply

Ground-Water Supply

Net Recharge

Water-Rights Allocation

Equal Appropriation with Specified Canal Diversions

Prior Appropriation with Simulated Canal Diversion

No Senior Farm Downstream of the Farm of Interest on the Same Canal

Senior Farm Exists Downstream of the Farm of Interest on the Same Canal

No Senior Farms Exist on Downstream Diverting Canal (Case A)

Senior Farms Exist on Downstream Diversion Canal (Case B)

Modification of Prior Appropriation System for Surface-Water Surplus

Drought Scenario Alternatives

Update of Source Term Flow Rates

Applicability and Limitations

General Data Requirements

Arrays and Lists of Spatially Distributed Data

Two-Dimensional Arrays

Ground-Surface Elevation

Identification Arrays

Multi-Dimensional Attribute Lists

Farm Wells

Stream Segments and Reaches

Data Requirements for Entire Simulation

Farm-Wells Data

Farm Data

Farm Irrigation Efficiency

Soil-Type Data

Crop-Type Data (Natural)

Root-Zone Depth

Fraction of Transpiration and Evaporation of Consumptive Use

Fraction of Inefficiency Losses to Surface-Water Runoff

Root-Uptake Coefficients for Stress Response Function

Specific Crop Coefficients

Climate Data

Crop-Type Data (Agro-Economic)

Crop-Type-Related Fallow Flags

Crop-Type Benefits Data

Water-Cost Coefficients

Surface-Water Data

Nonrouted Deliveries

Routed Deliveries

Semi-Routed Deliveries

Fully-Routed Deliveries

Stream-Reach Data

Data Requirements for each Stress-Period

Farm-Wells Data

Nonparameter or Parameter Farm-Wells Lists

Farm Irrigation Efficiencies

Crop-Type Arrays and Data (Natural Attributes)

Crop-Type Identification Array

Crop-Type Data

Climate Data

Precipitation Array

Crop-Type Data (Agro-Economic)

Crop-Type Benefits Data

Water-Cost Coefficients

Surface-Water Data

Nonrouted Surface-Water Deliveries

Routed Surface-Water Deliveries

Water-Rights Data

Data Input Instructions

Input Data for the FMP1

Data for each Simulation

Data for each Stress Period

Input Structure of Array and List Reading Utility Modules

Control-Record Item a

Control-Record Item b

Explanation of Fields Used in the Input Instructions

Dimensions and Flags (item 2)

Parameter Dimensions (item 2)

Farm-Well Related Variables (items 3, 4, 22, 23)

Farm Well Parameter Definition (item 3):

Two-Dimensional Arrays (items 5, 6, 8, 10, 25, 30)

Farm Related Data Lists (items 7, 19, 20, 24, 32, 33, 34, 36)

Soil Type Related Data List (item 9)

Crop-Type-Related Data List (Natural Crop Growth Parameters) (items 11-15, 25-29)

Climate-Related Data (items 16, 30)

Climate Time Series (item 16):

Precipitation Array (item 30):

Crop-Type-Related Data Lists (Agro-Economic Parameters) (items 17, 18, 31)

Fallow List (item 17):

Water Cost Coefficients (items 19, 32)

Ground-Water Cost Coefficients:

Surface-Water Cost Coefficients:

Nonrouted Surface-Water Deliveries–Farm-Related Data List (item 33)

Semi-Routed Surface-Water Deliveries–Farm-Related Data List (items 20, 34)

Surface-Water Allotment (items 35, 36)

Equal Appropriation:

Prior Appropriation:

Ouput Data for Farm Process

Farm-Well Budget

Farm Net-Recharge Budget

Farm Supply and Demand Budget

Optimized Flow Rates and Optimized Acreage of Farms

Budgets at Points of Canal Diversion and Farm Diversion

Example Problems

References Cited


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