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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
U.S. GEOLOGICAL SURVEY
Techniques and Methods 6-A17
Sacramento, California 2006
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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.
Abstract
Introduction
Irrigation Water Demand and Supply
Previous Simulation of Crop Demand and Irrigation Water Supply
Modeling Agricultural Irrigation Supply and Demand
Purpose and Scope
Acknowledgements
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
Appendix
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