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RGDSS Memorandum <br />Final <br />TO: Ray Bennett <br />FROM: Ed Armbruster, Hydrosphere, Erin Wilson, Leonard Rice Consulting Water <br />Engineers <br />SUBJECT: RGDSS Surface Water, Task 8.1 -Review Wells and Lands Served by <br />Groundwater Only <br />DATE: July 6, 2000 <br />CC: Randy Seaholm <br />Introduction <br />This memorandum represents delivery associated with Task 8.1 (Review Wells and Lands Served <br />by Groundwater Only). The objective of this task was as follows: <br />Review well inventory to identify those lands served only by groundwater. Select wells to <br />represent in the surface water model. <br />Methodology <br />Irrigated parcels that are outside of ditch service areas have been categorized as "ground water <br />only" parcels. These parcels are grouped together based on their location within a unit response <br />function zone (URF zone). The following procedure was followed, using ArcView, in the <br />development of ground water only aggregate structures: <br />1. The most recent irrigated parcel coverage (div3_irrparcels) attribute table was queried for <br />irrigated parcels that are not covered by a ditch service area. The query field, Ditchl_cov, is <br />blank if there is not an associated ditch system. Therefore, the query had to be performed by <br />choosing all Ditchl_cov records that were greater than 0, then using the "switch selection" <br />function in ArcView. <br />2. Parcels that match the query performed in Step 1 determined to have only a ground water <br />source were grouped based on the URF zone coverage (URFS12-15-99 arcview). The ID <br />in the URF zone coverage was assigned to each ground water only parcel based on its <br />location within a URF zone. This was completed by performing a spatial join between the <br />two themes. <br />3. In some cases, URF zones cross water district boundaries. Because it is valuable to aggregate <br />"structures" by water district in order to calculate and report consumptive use, the groups <br />identified in Step 2, above were further refined to not cross a water district. This was done by <br />performing a spatial join between the results of Step 2 and RGDSS wd theme. <br />4. The two fields (wd and urf~ were then combined using Arcview's calculator function to create <br />aggregate names such as " 20URF24". This example "structure" is in water district 20, URF <br />zone 24. <br />C:\cdss\Task8-l.doc Groundwater Only Lands July 6, 2000 -Page 1 of 5 <br />