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United States Department of Agriculture

Agricultural Research Service

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Research Project: FEEDBACK CONTROLLED-DRAINAGE SUBROUTINE INCORPORATED IN DRAINMOD-N2 MODEL TO PREDICT NITRATE LOSS IN DRAINAGE WATER MANAGEMENT SYSTEM

Location: Sugarcane Research Unit

2010 Annual Report


1a.Objectives (from AD-416)
1) Modify the current version of DRAINMOD-N2 by incorporating program code to simulate a feedback controlled-drainage mode of automated operation for drainage water management systems using various feedback signals, such as drain outlet water level, field water table depth, rainfall amounts and/or intensity, etc. 2) Conduct verification runs with the modified model using previous input data sets from the NCSU and ARS investigators, plus one or more Midwestern data sets, to insure the model runs remain stable and that simulated hydrologic functions are not changed by the incorporated program code when conventional subsurface drainage, fixed-weir controlled- drainage, and subirrigation modes are simulated. 3) Conduct preliminary runs with the modified model to simulate Nitrate transport (loss) in the controlled-drainage effluent when using input data sets available from the NCSU and ARS investigators, or other data sets that may be available, for comparison of simulated and field measured Nitrate loss in controlled-drainage.


1b.Approach (from AD-416)
• The ARS investigator will provide Fortran program code changes made in DRAINMOD ver. 3 (that did not include nutrient transport, only hydrology) during the late 1980’s to simulate automatic feedback-control adjustments of the outlet weir elevation, or desired controlled water level, at the subsurface drainpipe outlet in the controlled-drainage and subirrigation modes for automated water table depth control with respect to normal increases in crop root-zone depth during the growing season, and major changes in water table depth due to rainfall or drought. • The NSCU investigators will employ a Research Associate to assist in making the required program code changes/inserts in DRAINMOD-N2 and to conduct the verification and specified preliminary runs under direction of NCSU investigators. Note: The modified model should retain the procedure (routine) currently in DRAINMOD-N2 to change elevation (depth) of the outlet weir a specified distance via a step-wise adjustment on Julian date(s) listed in the input data set. • The ARS investigator will periodically review simulation results with NCSU investigators and Research Associate to ensure the automated operation is properly simulated with the modified model, and to make suggested changes as/if needed. • Upon completion of the above steps, a technical paper on the modified model will be prepared by the NCSU and ARS investigators for publication, and the paper should outline the additional steps needed to validate/calibrate the modified model for major geographic regions to account for differences in topography, climate, soils, crops, cultural and fertility practices, and water management system designs.


3.Progress Report

A Post-doc employed by the NCSU Principal Investigator (PI) prior to the initiation of this project was assigned to the project on the date (04/01/10) the Specific Cooperative Agreement was administratively approved, and he immediately began preparations to conduct the programming required for meeting the stated objectives. The ARS investigator (ADODR) provided four types of information, as follows: 1)the original DRAINMOD source code (ver..
3)that was modified by incorporating a feedback control subroutine; 2)the modified DRAINMOD source code with changes highlighted in red font print; 3)example input and output data sets used by the ADODR for computer simulation runs with the modified DRAINMOD code that had the incorporated feedback subroutine; and 4)several published papers by the ADODR and his colleagues or associates that reported the results of using the modified DRAINMOD model to simulate feedback controlled drainage and subirrigation systems. One paper described an alternative subroutine that allowed the input of weather forecast data for the period of rainfall record to simulate adjusting drainage or irrigation control, if needed, prior to forecast rainfall events. Most of this information was provided via attachments to E-mail messages and instructions sent to the PI, and some limited hard copies of documents were sent by mail or express mail. Several early communications occurred between the ADODR and the PI, the Post Doc’s two technical supervisors (both whom also work under the general supervision of the PI), and the Post Doc employee, to cover details on the materials and information provided, and to establish a means of providing periodic updates on progress to the ADODR. Most communications following the initial series have been via E-mail to ask or answer questions, and to obtain additional details as needed, but occasional phone calls are still needed and used to exchange detailed information and to ask/answer pressing questions that arise. The NCSU PI and the ADODR attended an engineering society meeting in June 2010 and used the opportunity to review details of progress made to date and to tentatively schedule a meeting for the Fall of 2010 to review and evaluate progress. The review meeting will be held at NCSU between the five key individuals working on the SCA project, and preliminary plans will be formulated for preparation of a final paper on the modified model and its function/purpose for presentation at an engineering conference and publication in an engineering journal. The project was monitored through emails, telephone calls, and site visits.


Last Modified: 12/20/2014
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