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MEMO 93 <br />to a well in 2001 will be tied to the same well for each historic period, as long as the well was <br />appropriated or permitted by the end of that irrigation year. The SPDSS team also agreed that it would be <br />reasonable to assign all groundwater-only land in 2001 to groundwater-only in the historic periods as <br />well. RTi developed a procedure and semi-automated routine to perform these objectives that involved a <br />series of ArcGIS models and scripts as described below. <br />RTi developed an ArcGIS model and python script to calculate groundwater attributes from the 2001 <br />parcel to the intersecting historic parcels, as shown in Appendix C.3. The model first created centroids <br />from the historic parcels, then intersected the centroids with the 2001 parcels and copied the 2001 parcel <br />ID to the historic parcel. The 2001 parcel ID was then used to join the historic parcels to the 2001 <br />parcels. The python script then calculated all groundwater attributes from the 2001 parcel to the joined <br />historic parcel. It also prevented well IDs that were not active in the historic period from being populated <br />in the historic parcels and removed any SW WDID entries for parcels that were groundwater only in <br />2001. The result for each historic period was a parcel dataset that had the same well assignments as the <br />corresponding overlapping 2001 parcels. <br />6.3.2 Assign Wells to Previously Unmapped Historic Parcels <br />Historic parcels that were unmapped in 2001 needed to have wells assigned. Since these parcels were not <br />mapped in 2001, they were not matched to a well as described in 6.3.1. A procedure was outlined with <br />the client to subset these parcels and put them into the StateDGI well-to-parcel matching program. This <br />procedure was documented and approved by the state in the memo, "Historic Well Assignment General <br />Procedure," dated August 25, 2006. <br />The first step in the procedure was to select previously unmapped parcels. This was done in a stepwise <br />approach: 1987 parcels were selected that were not mapped in 2001, 1976 parcels were selected that were <br />not mapped in 1987, and 1956 parcels were selected that were not mapped in 1976. The parcels that were <br />unmapped in 2001 but mapped in the subsequent historic year had well matches translated from the <br />subsequent year with the same procedure described in Section 6.3.1 of this memo. The parcels that were <br />still unmapped were then put into the StateDGI program. For parcels with only a surface water source, <br />the Type 1(well within the parcel) matches were retained. For groundwater-only parcels all of the <br />matches were retained. The next step was performed with aRTi-created script that reconciled the <br />matches of all parcels by removing Type 2 well matches from existing parcels when the well had been <br />matched to a previously unmapped parcel as a Type 1. Figure 12 shows an example of the well-match <br />reconciliation. The final step was to ensure that each parcel had a water source, either surface or <br />groundwater. <br />Page 22 of 59 ,Rrvera~Ge Feel~n81'agy, ioe. <br />