Optimal Conjunctive Management of Supplemental Irrigation Reservoirs and Cropland
Taylor, James A.K.
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https://hdl.handle.net/2142/69879
Description
Title
Optimal Conjunctive Management of Supplemental Irrigation Reservoirs and Cropland
Author(s)
Taylor, James A.K.
Issue Date
1987
Department of Study
Agricultural Economics
Discipline
Agricultural Economics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Economics, Agricultural
Abstract
Most claypan soil areas have inadequate groundwater supplies to provide wells for irrigation. Therefore, the establishment of reservoirs for storing rainfall and runoff water, seems to be the most likely source of irrigation water in such areas. However, the storage of runoff water for later reuse in the irrigation of crops when soil moisture supplies are low also means the storage of sediment carried in the runoff. Sediment deposited in a reservoir reduces its water-storage capacity and consequently, the amount of water available for irrigation of crops.
The purpose of this study, therefore, is to develop an analytical procedure for evaluating the feasibility of investments in facilities for supplemental irrigation such as reservoirs. The effects of the sediment carried in the runoff on reservoir water-storage capacity and how that in turn, affects the annual choice of management practices is also considered.
Two dynamic programming models, one structured for intraseasonal decision analysis of a one-crop system, and the other for interseasonal analysis of numerous management systems, are provided.
The intraseasonal DP model is used for determining optimal irrigation policies, i.e., when and how much to irrigate for corn growth within the growing season. From the optimal policies, different annual water use levels are generated, which are combined with different crop rotations, mechanical practices and tillage practices to form the crop management systems used in the interseasonal model as decision alternatives. The interseasonal model is used for choosing annual sets of management practices that maximize the present value of annual net returns to the reservoir.
The analysis indicated that irrigated production compared to dryland production is more profitable at low discount rates. For a specific study site, (S15T.3S-R.3W), near Pilot Knob in Washington County, Illinois, the analysis showed that investments in irrigation facilities yielded positive returns at discount rates of 4.00 and 7.125 percent. At a 12 percent discount rate, the net present value under irrigated production was negative.
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