CRDSS_Task1_15-17_ColoRiver_IrrigationReturnPatterns

Home Browse Search

CRDSS Memorandum Final To: Ray Alvarado From: LRE, Erin Wilson and Heather Justus Subject: Colorado River Basin Representative Irrigation Return Flow Patterns Date: January 20, 2003 Background Monthly irrigation return flow patterns were developed for use in the CRDSS water resources planning models using the Glover analytical solution for parallel drain systems and estimated parameters as outlined in the CRDSS Task Memorandum 1.15-17 (CRDSS Memo 1.15-17) finalized in January 1995. The three monthly irrigation return flow patterns recommended in this memorandum differ from the return flow patterns eventually used in the CRDSS modeling efforts. Backup documentation regarding the development of the return flow patterns used in the CRDSS modeling efforts, as defined in the StateMod delay pattern input files (*.dly), was not found. The CRDSS water resources planning models are being enhanced to simulate using a daily time- step, therefore, daily return flow patterns are required. Initially, the recommended approach was to 1) determine the alluvial aquifer characteristics used to develop the monthly return flow patterns defined for the CRDSS modeling efforts, then 2) develop daily return flow patterns using the same parameters. This approach was followed in the development of daily return flow factors for the Yampa River Basin, as documented in the July 6, 2001 CRDSS Daily Yampa Model Subtask 1-Equivalent Daily Return Flow Factors Memorandum (Daily Yampa Memo). As noted in this memorandum, Glover parameters were chosen such that the monthly delay pattern would closely match the delay pattern "1" used in the CRDSS basin modeling efforts. Introduction The purpose of this task was to develop return flow patterns for both the monthly and daily CRDSS planning models using geologic parameters representative of actual locations of irrigated acreage in each of the five CRDSS basins and a methodology that is acceptable and can be reproduced. Two return flow patterns were developed to represent irrigated lands relatively close to a live stream, and irrigated lands further from a live stream. The Glover solution for estimating accretion to the stream due to recharge of an alluvial aquifer was used for the analyses. This method is commonly used to determine return flow patterns and is believed to appropriate for this task. The State's Analytical Steam Depletion Model, developed by Dewayne R. Schroeder (September 1987), was used to perform the analyses. This model allows options to determine both monthly and daily accretion factors (return flow patterns), and is widely used in determining return flows for water rights transfers and augmentation plans. Pagelofl2