WSP03745

• File Number: 8111.815
• Description: Arkansas River Compact Administration
• Basin: Arkansas
• Date: 4/1/1990
• Author: UCACOE
• Title: Drought Contingency Plan - John Martin and Trinidad Lake - Appendix D
• Water Supply Pro - Doc Type: Publication

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SECTION III . DROUGHT IDENTIFICATION

3-01. Historical.

a. General. . For the purpose of this plan a drought is defined as a
climatically induced water shortage. It is generally of wide areal coverage and
its impacts are usually over a large spectrum of interests. The information
contained here relates specifically to naturally developed historical shortages.
The development of an isolated shortage at a specific location caused by the
overuse of the resource. while in a normal climatic pattern, . is considered a man-
made event. Such shortages are not considered in this document and are tr~ated
through routine water management procedures and coordination channels.

The Corps projects in the Basin were designed to provide a dependable
irrigation water supply based on the period of record available during design.
A more detailed discussion on design of the conservation storage is provided in
paragraph 4-02b and 4-02c for John Martin Reservoir and Trinidad Lake,
respectively.

b. Experienced Droughts. Although droughts are naturally occurring events
in the Arkansas River Basin, little is known about their occurrence prior to the
last decade of the 19th century. Climatic records kept prior to this period are
not sufficient to show the nature of the droughts.

Generally, these records are sporadic and few in number. The Palmer
Drought Severity Index (PDSI) has been calculated for each month from historical
records. This index is used by the National Weather Service (NWS) as an
indicator of the severi ty of a drought. A more detailed discuss ion of this
indicator is included in paragraph 3-02. Plate 3-1 shows the climatic divisions
for the PDSI in Colorado. By using this measure of severity, droughts can be
categorized as mild, moderate, severe or extreme. The droughts in these
categories and their duration in months, are shown in Table 3-1. The drought
periods shown on Table 3-1 are for the Arkansas River Drainage (NWS Climatic
Division # 1) in Colorado.

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rablo 3-1
Arkansas River DratnRge
Hlat~rlcal Drou&ht Periods
DROUGHT PERIOD NUKBER OF HONTHS TOTAL HONTHS
IIAIII 11m "1IUIl MODUATI W1RI EXTREME
Au! 1900 May 1903 10 14 8 2 34
Ju1 1931 Rov 19 37 3 20 19 33 75
Jun 1939 AUK 1940 2 7 6 15
Rov 1949 Har 1957 10 9 37 31 87
Mar 1962 Mar 1965 3 6 9 19 37
Mar ,1966 Apr 1969 19 13 5 37
Jun 1971 Apr 1972 10 1 4 15
Har 1974 Oct 1978 19 22 9 50
Apr 1980 Apr 1982 -1 -1 -11 -l -1l
Total 79 97 108 87 371

*8.8 T.ble 3-3 for description. of .lld to extre.. drou&ht.
3-1