SPDSS_Task74_EstimateGroundwaterSprinklerIrrigatedAcreage

• Title: SPDSS Task 74 - South Platte Historic Consumption Use - Annual Irrigation Parameter Time Series ‎(Ground Water Acreage and Sprinkler Acreage)‎
• Description: This memorandum presents the general approach to fill missing irrigated acreage data for the SPDSS.
• Decision Support - Doc Type: Task Memorandum
• Date: 3/27/2007
• DSS Category: Consumptive Use
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153954
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: Leonard Rice Engineering

Observed differences between the two filling approaches are:
Sub'ect Acrea a Fillin A Acrea a Fillin B
Acreage Total acreage remains constant for Total acreage changes between acreage
Transition structures with surface water. Abrupt snapshots; smooth transitions.
changes at acreage snapshots.
Acreage Controlled by well appropriation date Controlled by snapshot distributions
Subset and snapshot distributions; abrupt only; smooth transitions.
Transition changes at snapshots.

Sub'ect Well Ca acit Fillin A Well Ca acit Fillin B
Total Well Controlled by wells assigned to the Controlled by wells assigned to acreage
Capacity structure and well appropriation date. in each snapshot and linearly
connecting the capacities.
The consumptive use analyses performed showed that the differences in total well capacity did
not limit pumping in any year between 1950 and 2005.
Recommendations
We recommend using Acreage Filling B (Linear Interpolation) with sprinkler acreage set to zero
in 1969 and Well Capacity Filling A (Decreed based on when wells became active), as described
in the approach section.
1. The Acreage Filling A uses well appropriation date as the basis for acreage subset changes
between snapshots. However, there are some inconsistencies in the well assignment process
that causes abrupt changes at the year representing the snapshots. For instance, there are
structures that have wells assigned in the 1987 and 1956 snapshots that have an appropriation
date of 1955. However, these wells were NOT assigned to acreage in the 1976 snapshot.
2. The Acreage Filling A is complex and will be difficult to code in StateDMI, therefore
difficult to test. More importantly, the approach will be difficult to explain to water users
and other interested parties.
3. Amore complex approach may signify to users that we have more confidence in the filled
data than a simpler approach would indicate.
Comments and Concerns
The filling procedures recommended in this memorandum assure consistency with total acreage
and crop type filling algorithm recommended in the Task 71 memorandum.