WSP08526

• File Number: 8543
• Description: Closed Basin Division
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 11/13/2002
• Title: Operating Committee Meeting - Hydrologist Report
• Water Supply Pro - Doc Type: Report/Study

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001881

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Operating Committee Meeting
Hydrologist Report
November 13, 2002

OBSERVATION WELL DATABASE
Since 1993 the only observation well database maintained by the USBR has been the Elevation Well (EW)
network. The EW well network was constructed in stages, beginning with stages 1&2 in 1980-81. Stage 3
was constructed in 1982-83 and stages 4&5 were completed in 1983-1984. In addition to these wells, 14
Pilot Wells (PW's) were converted to EW's (EW#'s 69-82; Only the confined wells were monitored at these
locations). This brought the total number ofEW wells to 134 (67 confined & 67 unconfined). In 1994,7
new confined wells were drilled at selected EW sites. Also, monitoring was discontinued at one unconfined
well (EW13) and one confined well (EW28). This resulted in a total of 80 EW well sites:
52 sites have both CON & UNC wells [including 7 sites with original CON well (C-l) and new CON
well (C-2)]
14 sites with CON wells only (EW#69-82)
14 sites with UNC wells only (EW#2, 4,6,7,8,12,14,15,17,18,19,21,23, & 25)

However prior to construction of the EW well network, the USBR had a different observation well network.
This network consisted of:
(25) Pilot Wells (PW's): These were all "confined" aquifer monitoring wells, some were artesian
(25) "OW" Wells: These were shallow unconfined observation wells located at the PW well sites.
(30) "OW-A" Wells: These were shallow unconfined observation wells located at Test Well (TW) sites.
(11) Other shallow unconfined wells located in stages 3, 4, & 5.

As mentioned before 14 of the "PW" wells were converted to "EW" confined wells (EW#69-82). However
monitoring at all other well sites was discontinued over the years. I have tried to locate these wells in order
to re-establish monitoring at these sites. I was able to locate all of the "PW" wells and many of the UNe
wells. However the UNC wells are just 1-1/2" PVC pipes sticking out of the ground and many have been
destroyed. To date monitoring has been re-estabJished at 42 wells:
(3) EW_CON Wells (old PW wells) at EW# 06,18, & 21
(11) EW_UNC wells (old OW wells) at EW#,69,70, 71, 72, 73, 74, 75, 76, 79,80, & 82
(14) PW Wells, this includes 7 sites with both CON & UNC Wells
(14) OW Wells, These are shallow UNC wells 1-1/2" PVC pipe

These additional wells will provide more complete spatial data (filling in gaps between EW wells) as well as
a longer period of record (records begin in 1978 compared to 1980 to 1984 for EW wells).

This additional data along with data from the RGWCD and USGS unconfined wells within the elosed Basin
Study area (see map) will be used to generate new, more detailed, unconfined aquifer change and
potentiometric surface maps.

The USGS wells and the old USBR wells still need to be surveyed for elevation and location to tie them into
the existing EW and RGWCD grid. This should be completed this spring and the new maps should be ready
for the next operating committee meeting.