PROJ00132

• Contract/PO #: FS0014X
• Contractor Name: Southern High Plains Ground Water Management District
• Contract Type: Loan
• Water District: 0
• County: Prowers
• Loan Projects - Doc Type: Feasibility Study

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

5.0 ESTIMATE OF IRRIGATED LANDS AND RELATED WATER USE

5.1 IRRIGATED LANDS
Beck (1967) estimated that a total of 70,000 acres were irrigated from both ground and surface
water sources in 1966. Based upon records from the Baca, Las Animas and Prowers County
Assessors Office, MWE (1999) reported a total of 106,300 acres of irrigated land within the
District and a total of 128,500 acres within the Basin.

Satellite imagery and GIS (ARC-VIEW) tools were used to compare the number of irrigated
acres at two different time periods, August 1989 and August 1999. Comparisons of the
interpretation for the two periods are summarized in Table 5-1 and are shown in Map 6. This
comparison confirms visible changes in the number of acres being irrigated, the portion of the
growing season the irrigation was used, and the type of irrigation methods utilized by irrigators.
A review of the satellite imagery indicates there were approximately 39,400 acres being irrigated
in 1989. Of this total, 10,400 acres appeared to have had winter wheat planted and already
harvested at the time the satellite image was taken. The remaining 29,000 acres were planted
to corn or other crops that were being irrigated during August 1989. A similar interpretation of
the August 1999 satellite imagery indicated there were approximately 94,600 acres being
irrigated. Of this total, approximately 18,100 acres were interpreted as already harvested and
assumed to be irrigated wheat. MWE interpreted the remaining acreage, 76,500 acres, to be
planted to corn or other crops that were being actively irrigated in August 1999.

Using the satellite imagery, MWE made a visual comparison of a 100-square mile area
southeast of Stonington to determine the number of center-pivot sprinklers in place in 1989
versus 1999. In 1989 there were 14 center pivots observed (14 pivots x 122 acres = 1708
acres) in the area; in 1999 there were 57 center pivots observed, including three center pivots
covering full sections (54 pivots x 122 acres + 3 pivots x 488 acres = 8052 acres). This visual
comparison indicates there has been both a change in the type of irrigation method being used
and what appears to be a 3-fold increase in the number of acres being irrigated by center pivots
in this 100-square mile area during the 1 O-year period.

Ideally, interpretation of satellite imagery should also be done in conjunction with site-specific
field inspection to verify the satellite imagery. This field inspection could not be done since the
Landsat photos were obtained prior to the actual study. However, for general comparison
purposes, the satellite imagery and the Baca County Assessor's office both show an increase in
the number of acres being irrigated and the crop selections that are being irrigated in the
District. The Baca County assessor's office shows 52,900 acres irrigated in 1989 and 106,300
acreS in 1999. Data also indicates more water was being used in the District in 1999 than was
being used in 1989.

V-1