WSP07833

• File Number: 8142.600.30.A
• Description: Other Studies - Purgatoire River Transit Loss Study
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 6/1/1953
• Author: Corps of Engineers
• Title: Review Report on Survey for Flood Control - Volume I
• Water Supply Pro - Doc Type: Report/Study

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paths or invading air masses from the several source regions, result in

the occbfrehc~ df several storm types or combinations of storm types over

the watershed, These storms may be divided into two classifications: the

f~ontal storm, resulting from frontal activity of two or more air masses,

and the thunderstorm (local summer storm) resulting from orographic or

convective lifting. The frontal storms are further subdivided into two

types: a cyclonic wave developing on a cold front or stationary front, and

a second type which is characterized by a front aloft. Each of these

typeS may cover ~ large area. The former general~ produces moderate pre-

cipitation intensities and shows the effects of orographic influence;

during the latter type, precipitation intensities may be high at random

locations within the storm area which seenlS to indicate a series of local

storms over relative~ large areas. Summer thunderstorms are most active

during July and August. The surface winds associated with summer thunder-

storms are usual~ 30 to 40 miles per hour, and in extreme cases may ex-

ceed 60 miles per hour.

33. Runoff. - Purgatoire River above Trinidad, Colorado, is peren-

nial. As is characteristic of most streams originating in the high

sierras, the greatest volume of runoff is produced by melting of the snow

blanket during April, May, and June. Thunderstorms produce floods with

high peaks and relatively small volumes. These usually occur after the

snow-melt season. he cords indicate that hydro graphs of floods resulting

even from general storms are extremely sharp with high peaks.

34. Seventeen stream gaging stations have been operated intermit-

tently on the Purgatoi~e River and tributaries. Records prior to 1921

were of.the staff or chain gage type but the majority of the gages opera-

ted since 1921 have been of the recording type. Discharge records are

available for 31 water years at Trinidad. A staff gage was maintained at

Alfalfa, river mile 122, from 1905 to 1907, and from 1924 to 1928, and was

re-established as a recording gage in 1952. The next station downstream

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