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eff• - conveyance eff• application eff <br />Where: SW ccnveyanceeff. =User Input (maximum) <br />SW applcation eff. = Crop Demand <br />Headgate Delivery <br />The Consumptive Use Contractor identified that, in several areas, a combination of application <br />techniques was used to apply water from groundwater wells. As such, groundwater efficiencies <br />were determined using the following approach: <br />GW eff = <br />(GW Lands Flood Irrigated) * 0.60 + (GW Lands Sprinklered) * 0.85 <br />Total Ground Water Land Acreage <br />The Phase lc model and subsequent model development phases include efficiencies calculated <br />using these methods and represent average monthly efficiencies over the 1950-1997 study period. <br />Model Execution Sequence <br />Following development of input data sets to reflect the addition of groundwater well use, <br />StateMod was run using the three-step process described in the memorandum documenting Task <br />Phase la model development (Task 6.14). That is, the model was first executed in baseflow <br />mode, followed by data check mode, and finally the model was run in simulation mode. This <br />three-step process (baseflow, check, simulation) may be repeated numerous times during model <br />calibration efforts. <br />Phase 1c Model <br />As previously described, the Phase lc surface water model for the Rio Grande Basin represents <br />100 percent of the surface water and groundwater use in the Rio Grande Basin from its <br />headwaters to the Colorado-New Mexico stateline. In this phase of development, the model was <br />executed in baseflow, check and simulation mode over the period 1950 to 1997. During this <br />period, historical flow observations at numerous gages, recorded water deliveries to diversion <br />structures, historical pumping by groundwater wells, and historical reservoir end-of--month <br />contents were used to develop baseflow hydrologic conditions. The model was then run in <br />simulation mode using historical diversions and well pumping as a surrogate for water demand. <br />This "historical simulation" that uses historic data and estimates as a surrogate for demand is <br />appropriate for a sequential calibration approach but will not be used for calculated demand <br />scenarios. In addition, this "historical simulation" includes numerous operating rules to reflect <br />water management practices over the study period. <br />Model calibration can be defined as simulating a system such that results agree reasonably well <br />with historical observations. The Rio Grande Surface Water Model was calibrated through <br />several adjustments to hydrologic conditions (baseflows) and operating rules. Efforts towards <br />calibration focused on three areas: comparison of historical to modeled diversion amounts, <br />comparison of historical to modeled stream flows, and comparison of historical to modeled <br />reservoir contents. The calibration period extended over the entire study period (1950 - 1997). <br />Due to improvements in data collection and changes in river administration, the most recent 20 <br />C:Acdss\Task8-8.doc Phase lc Model September 27, 2000 -Page 6 of 17 <br />